CIBSE Lighting Guide LG6:1992 "The Outdoor Environment"

LIGHTING GUIDE 6

THE OUTDOOR ENVIRONMENT

LG6: 1992

CIBSE The Chartered Institution of Building Services Engineers Delta House, 222 Balham High Road, London SW12 9BS

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The rights of publication or of translation are reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means without the prior permission of the

Institution.

0 1991 THE CHARTERED INSTITUTION OF BUILDING SERVICES ENGINEERS

LONDON

ISBN 0 900953 53 5

This document i s bored upon the best knowledge ovoilnble nt the time of publicotion. However no responsibility of ony Und for ony injury, deoth, loss, domogeordeloy however caused resulting from the useaftheserecommendo~onrcon be accepted by the Chortered Institution of Building Services Engineers, the authors or others involved in its publicotion. In adopting these recommendations for use each adopter by so doing ogreer to accept full responsibility for any personol injury,

deoth, loss, damage or deloy orising out of or in connection with their use by or on beholf of such odopter inerpective of the cause or reoson therefore ond agrees 10 defend, indemnify and hold hnrmless ihe Chartered Institution of Building Services Engineers, the oufhors and others invoked in their publication from ond agoinst any and 011 liability orising out of or in connection with such use 0s oforesoid ond irrespdve of any negligence on the pad of those indemnified.

Printed in Great Britain by Mayhew McCrimmon Printers Ltd, Great Wakering, Essex

Conients

1 Scope

2 Introduction

3 General design aspects

3.1 Aesthetic considerations 3.2 Functional considerations 3.3 Factors affecting the visual environment

4 Specific applications

4.1 4.2 Covered precincts and arcades 4.3 4.4 Vehicle parks 4.5 Outdoor work and storage 4.6 Railway and coach stations 4.7 Hospitals and health care 4.8 Banks and building societies 4.9 Educational precincts 4.1 0 Community buildings 4.1 1 Hotels, motels and restaurants 4.12 Garage forecourts 4.1 3 Subways, stairways, public footpaths 4.1 4 Roads and associated areas 4.1 5 Tunnel approaches and entrances 4.1 6 Parks and gardens 4.1 7 Structures 4.1 8 Statues and sculpture 4.1 9 Monuments and memorials 4.20 Clocks and sundials 4.21 Flags 4.22 Fountains and pools 4.23 Festive illuminations 4.24 Outdoor bandstands and auditoria 4.25 Son et lumiere 4.26 Illuminated signs and hoardings

Shopping precincts and pedestrian areas

Business parks and commercial zones

5 lighting techniques

5.1 5.2 5.3 5.4 5.5 5.6 5.7

Area lighting Lighting for amenity Floodlighting of buildings, structures and features Emergency lighting Security lighting Roadway lighting Landscape lighting

6 Equipment

6.1 Lamps 6.2 Luminaires 6.3 Control gear 6.4 Supports 6.5 Control 6.6 Electrical installation

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10 12 14 14 16 16 17 18 19 20 21 23 24 27 29 30 31 32 33 35 36 37 38

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41 42 43 51 53 56 58

58 58 61 65 65 66 68

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7 Maintenance

7.1 Commissioning the system 7.2 lamp depreciation 7.3 luminaire depreciation 7.4 Economics 7.5 System management

Appendix 1 Floodlighting design and calculation methods

Appendix 2 Landscape design method

References

Bibliography

Glossary

72 72 72 73 74 75

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80

81

82

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Index

Foreword

The Guide deals with many technical and aesthetic aspects which are likely to be of interest to users and specifiers of lighting equipment in outdoor situations. The aim of the Task Group has been to offer relatively simple ideas to avoid homogenised lighting solutions by presenting the basic visual problems and individual characteristics of a wide range of outdoor lighting applications. The designer is encouraged to evaluate the visual need and to consider artificial lighting and its associated equipment as an integral component of the complete landscape.

The Task Group wishes to acknowledge the individual contributions to the Guide provided by:

Lou Bedocs Arthur Elliott Clive Goodier Bob Hargroves Tom Howcroft Peter Lovett Derek H Phillips Andre Tammes Alan Tulla

and also to acknowledge the time and facilities provided by Thorn Lighting Limited.

Task group

P T Le Manquais Chairman J A M Bell G D Worthington

Publications Secretary K J Butcher

Co-ordinating editor V P Rolfe

The outdoor environment 1 Scope

The last application guide dealing with the practice of exterior lighting was published by the Illuminating Engineering Society in September 1975 under the title The Outdoor Environment. It was intended principally to benefit pedestrians in their outdoor environment during the hours of darkness. The document provided valuable assistance for designers to reach decisions about how they may enhance safety and visual pleasantness in urban and rural districts by lighting.

This new outdoor Lighting Guide takes account of changing demands through the broader scope of its content. It offers guidance and reference data useful for crime prevention officers, homewatch scheme co- ordinators, buyers and users, and more technical information needed by electrical engineers, town planners, developers, traffic engineers, lighting designers, architects and specifiers. It will also provide students with a greater appreciation of the problems and application techniques appropriate to outdoor lighting.

Section 3 discusses general design aspects by examining the lighting objectives in terms of aesthetic and functional considerations. This forms the basis for all the specific applications which are reviewed in Section 4. These include the lighting of parks and gardens, urban areas, and various types of buildings and structures. Festive and advertising lighting is also covered in this section.

Section 5 discusses the range of techniques used in some detail, area lighting amenity, security and emergency lighting. Section 6 reviews equipment from lamps, luminaires and controls to housings and masts. Section 7 deals with matters of maintenance and economic factors. Appendices deal with lamp and Iuminaire data, control gear, floodlighting and landscape design methodology.

Roadway lighting, traffic, advertising sign illumination and security lighting are included in this Guide but reference is provided to other publications which contain more comprehensive information. Lighting for construction sites, industrial lighting for exterior working areas and outdoor sports lighting are not included as these applications are dealt with fully in other separate CIBSE Guides and these are listed in the Bibliography.

It is hoped that the users of this Guide will find its practical data and advice purposeful and constructive in helping to achieve a good lighting solution which effectively satisfies all design aspects.

2 Introduction

The last decade has seen a change in the order of priorities that designers and specifiers apply to outdoor lighting installations. The overall annual running costs are no longer associated purely with capital outlay and energy charges. Present-day trading pressures, financial stringency and lower staffing levels are forcing all businesses and organisations to be much more judicious in the use of resources - human, financial and energy. On the other hand, the benefits for the purchaser of night-time exterior lighting now extends far beyond the simple experiences of pleasantness, amenity

1

The outdoor environment 1 Scope

The last application guide dealing with the practice of exterior lighting was published by the Illuminating Engineering Society in September 1975 under the title The Outdoor Environment. It was intended principally to benefit pedestrians in their outdoor environment during the hours of darkness. The document provided valuable assistance for designers to reach decisions about how they may enhance safety and visual pleasantness in urban and rural districts by lighting.

This new outdoor Lighting Guide takes account of changing demands through the broader scope of its content. It offers guidance and reference data useful for crime prevention officers, homewatch scheme co- ordinators, buyers and users, and more technical information needed by electrical engineers, town planners, developers, traffic engineers, lighting designers, architects and specifiers. It will also provide students with a greater appreciation of the problems and application techniques appropriate to outdoor lighting.

Section 3 discusses general design aspects by examining the lighting objectives in terms of aesthetic and functional considerations. This forms the basis for all the specific applications which are reviewed in Section 4. These include the lighting of parks and gardens, urban areas, and various types of buildings and structures. Festive and advertising lighting is also covered in this section.

Section 5 discusses the range of techniques used in some detail, area lighting amenity, security and emergency lighting. Section 6 reviews equipment from lamps, luminaires and controls to housings and masts. Section 7 deals with matters of maintenance and economic factors. Appendices deal with lamp and Iuminaire data, control gear, floodlighting and landscape design methodology.

Roadway lighting, traffic, advertising sign illumination and security lighting are included in this Guide but reference is provided to other publications which contain more comprehensive information. Lighting for construction sites, industrial lighting for exterior working areas and outdoor sports lighting are not included as these applications are dealt with fully in other separate CIBSE Guides and these are listed in the Bibliography.

It is hoped that the users of this Guide will find its practical data and advice purposeful and constructive in helping to achieve a good lighting solution which effectively satisfies all design aspects.

2 Introduction

The last decade has seen a change in the order of priorities that designers and specifiers apply to outdoor lighting installations. The overall annual running costs are no longer associated purely with capital outlay and energy charges. Present-day trading pressures, financial stringency and lower staffing levels are forcing all businesses and organisations to be much more judicious in the use of resources - human, financial and energy. On the other hand, the benefits for the purchaser of night-time exterior lighting now extends far beyond the simple experiences of pleasantness, amenity

1

CIBSE LIGHTING GUIDE

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and the stimulation that comes from an attractively lighted night-scape both for private and public organisations. A large part of the responsibility for the provision and operation of outdoor lighting rests with the local authorities. Many authorities now have special problems related to the night-time environment that warrant urgent and serious consideration. Very many of these authorities stand to gain significant benefits from improved exterior lighting. Increases in the incidence of crime and anti- social activity in the inner city and urban residential areas have emphasised the pressing need for improved amenity, safety and security.

On the brighter side, towns and cities are now being given a new lease of life with shopping malls and large zones totally free from vehicular traffic. Architects and planners have the scope for building a new and exciting character into these new areas with emphasis on increased attractiveness, coupled with safety and security, encouraging a sense of local pride and well-being.

It is important for the designer to note therefore that, although the expression ‘functional outdoor lighting’ may be used to describe any type of exterior lighting that is intended to do a task rather than for its visual effect, a design with empathy will almost always produce an overall enhancement of the visual environment.

This Guide accepts the view that there is an awareness that much of our present outdoor lighting practice, particularly in the more sensitive areas, is no longer acceptable. There is now a challenge for the lighting designer to ensure that his knowledge and skill is utilised fully for the benefit of the entire community.

General design aspects

The basic objectives of the outdoor lighting described in this guide are to promote safety and security at night, enhance appreciation and enjoyment of the surroundings and, by giving a sense of belonging, help people to relax.

To achieve these objectives, adequate and properly distributed light of suitable colour is needed to display the form and characteristics of principal features in a satisfying manner, reveal clearly such hazards as changes of level, illuminate dark and potentially dangerous areas, and enable full advantage to be taken of opportunities for entertainment, culture and leisure.

Often a small amount of light can fulfil the needs, indeed the effects may be spoilt by having an excess. The desirable balance between the various lighted areas is a matter of subjective judgement rather than engineering expertise; an appreciation of the visual effects is called for both on a large scale and when lighting individual features. In general, calculations are subservient to experience when dealing with the types of lighting discussed in this Guide.

The designer’s task first is to identify clearly the objectives of the proposed lighting project and then to consider how these can be met by applying the principles described. Often well designed lighting will satisfy objectives other than the main one. For example, urban street lighting may not only serve the safety needs of drivers and pedestrians but also light surrounding buildings so that the whole environment is more pleasing. The best results are usually achieved when individual schemes are co-ordinated with the lighting plan for a whole district, and when the designer is able to

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and the stimulation that comes from an attractively lighted night-scape both for private and public organisations. A large part of the responsibility for the provision and operation of outdoor lighting rests with the local authorities. Many authorities now have special problems related to the night-time environment that warrant urgent and serious consideration. Very many of these authorities stand to gain significant benefits from improved exterior lighting. Increases in the incidence of crime and anti- social activity in the inner city and urban residential areas have emphasised the pressing need for improved amenity, safety and security.

On the brighter side, towns and cities are now being given a new lease of life with shopping malls and large zones totally free from vehicular traffic. Architects and planners have the scope for building a new and exciting character into these new areas with emphasis on increased attractiveness, coupled with safety and security, encouraging a sense of local pride and well-being.

It is important for the designer to note therefore that, although the expression ‘functional outdoor lighting’ may be used to describe any type of exterior lighting that is intended to do a task rather than for its visual effect, a design with empathy will almost always produce an overall enhancement of the visual environment.

This Guide accepts the view that there is an awareness that much of our present outdoor lighting practice, particularly in the more sensitive areas, is no longer acceptable. There is now a challenge for the lighting designer to ensure that his knowledge and skill is utilised fully for the benefit of the entire community.

General design aspects

The basic objectives of the outdoor lighting described in this guide are to promote safety and security at night, enhance appreciation and enjoyment of the surroundings and, by giving a sense of belonging, help people to relax.

To achieve these objectives, adequate and properly distributed light of suitable colour is needed to display the form and characteristics of principal features in a satisfying manner, reveal clearly such hazards as changes of level, illuminate dark and potentially dangerous areas, and enable full advantage to be taken of opportunities for entertainment, culture and leisure.

Often a small amount of light can fulfil the needs, indeed the effects may be spoilt by having an excess. The desirable balance between the various lighted areas is a matter of subjective judgement rather than engineering expertise; an appreciation of the visual effects is called for both on a large scale and when lighting individual features. In general, calculations are subservient to experience when dealing with the types of lighting discussed in this Guide.

The designer’s task first is to identify clearly the objectives of the proposed lighting project and then to consider how these can be met by applying the principles described. Often well designed lighting will satisfy objectives other than the main one. For example, urban street lighting may not only serve the safety needs of drivers and pedestrians but also light surrounding buildings so that the whole environment is more pleasing. The best results are usually achieved when individual schemes are co-ordinated with the lighting plan for a whole district, and when the designer is able to

2


collaborate closely throughout a project with the architect, landscape architect, consulting or municipal engineer and the client.

The following issues affect the way in which people respond to the visual environment.

3.1 Aesthetic considerations

3.1.1 Unity

3.1.2 Key

3.1.3 Scale

Unity or cohesion between elements in a scene can be achieved by a carefully conceived design theme. Once a theme is established it will guide the development from the overall lit effect to the selection of appropriate equipment with regard to scale, shape, material and colour. See plate 1.

A high key scene has mainly bright tones, having high reflectance finishes with reasonably high values of illuminance which is fairly evenly distributed. A low key scene has mainly dark tones which may be provided by the finishes or by intentional variations of illuminance giving contrast between dark and light areas. The key selected will be related to the function of an area and the reflectances of its various surfaces. For example, in response to different sets of requirements an urban area may be generally bright with high lighting levels whereas a country district could call for a lower key approach in keeping with the surroundings.

Scale concerns the perceived size of building elements or spaces relative to other forms or to people. As lighting at night can be selective, the scale interpretation of an environment can differ from that by day. An intimate, friendly, scale can be created by controlled contrasts in luminance, pools of light related to significant areas such as individual dining tables or a cafe terrace or seating areas where pathways meet. In urban areas the contrast could be between lighting in streets leading to a major square and that of the square itself. The more general the lighting the more normal the sense of scale. Lighting can emphasise the scale of the environment or a building. For example, a building where only selected features are lit could have an intimate smaller scale appearance than when totally floodlit, its impressive mass dominating the view. The effectiveness of scale depends upon relationships which are created within the visual field. See Plate 2.

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Figure 3.1. Torquay pavilion. Small light sources outlining key architectural features create an appropriate festive air for a seaside pavjlion.

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3.1.4 Rhythm

3.1.5 Emphasis

3.1.6 Modelling

3.1.7 Enclosure

The spacing of lighted elements, lighting fittings, posts and pools of light are perceived as rhythms. The wider the spacing, the slower the beat, the more solemn the response; festive lighting uses faster, complex rhythms usually composed of small elements at short intervals.

By selective lighting the unattractive can be played down or eliminated whilst attractive features can be emphasised. Attention can be drawn to significant features, a facade within an urban square, or major buildings of a town viewed from approach routes. The degree of emphasis will depend upon a composed balance from each main viewpoint and will be related to the general background lighting. Surface texture and the form of an object can be emphasised by creating modelling effects.

The highlights and shadows that give life to a scene and achieve modelling are created by the luminous intensity and direction of light in relation to the form and texture of the surface and the direction of view. The impressions are subjective and cannot be measured.

A dramatic effect can be achieved by directing floodlights at a glancing angle to produce strong shadows and marked highlights. Modelling is severely diminished, if not totally lost, when the direction of viewing coincides with that of the lighting.

In practice there may be several positions from which a building, a sculpture or a tree may be viewed and so an order of importance has to be determined. If a building can be approached from two directions it may be appropriate to have a ‘warm’ side and a ‘cool’ side, by providing subtle changes in order to stress its three dimensional form.

Vertical surfaces contribute strongly to the sense of enclosure and direction. Openings provide continuity with adjacent spaces, visually and sometimes physically. To give coherence to the relationship and connections the lighting of vertical surfaces demands special consideration. See Plate 3.

3.1.8 Sequence and direction Interest can be created in moving through a sequence of spaces by variation in the lit effects, key, colour, luminance, modelling, etc.. For example, moderately lit streets with pools of light on wall surfaces could lead into a brightly lit square with floodlit buildings. The eyes, or wandering feet, of tourists may be led to the next important feature by emphasising the route with regularly spaced bollards or post top lanterns. An avenue might be indicated by lighting the trees with a glimpse of high brightness at the end of the vista to encourage further exploration. See Plate 4.

3.1.9 Depth

3.1.1 0 Colour

The effect of distance can be increased or reduced by the luminance or colour of juxtaposed objects. A more informal, less regular, arrangement of illuminated surfaces can give the effects of depth in landscape lighting. The use of silhouette, interesting in itself, also helps to change the apparent relationships between objects in a field of view.

There are two important characteristics of colour related to lighting which affect .response. Firstly, the colour appearance of the light source or reflected light can evoke a warm or cool atmosphere. Lamps of low correlated colour temperature are seen as warm, those of high correlated colour temperature as cool. Secondly, colour rendering, the way in which colours are perceived when illuminated by a light source is usually related to their appearance under daylight. An insensitive or inappropriate use of colour can cause great dissatisfaction. The use of colour in building or landscape floodlighting is largely a matter of personal taste. Multi-coloured floodlighting might be appropriate to reflect the bustle of a city centre but would destroy the tranquillity of a country town; a parish church would

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look incongruous in a colour scheme which would be more suitable for a public house.

Colour can be used in many ways. It can colour shadows from a different light source, it can emphasise stepped constructions and it can provide contrasting backgrounds for other lighting. From a practical point of view, white or near white buildings can be lit to any colour, but complementary colours of light and fabric are rarely successful. Thus blue light on red brick will be ineffectual and whilst red light on red brick will appear quite bright, it should be considered whether the coloured light is really adding anything to the intrinsic colour of the brick. This applies mainly to colour obtained by filters. High Intensity Discharge (HID) lamps have their own intrinsic colour and lose nothing in efficacy.

In general, colours in the outdoor environment at night are required to be recognisably natural, and for this reason a ‘white’ source is normally used. However the spectral distributions of light emitted by typical ‘white’ lamps show quite notable differences from warm to cool, so that the designer can produce subtle contrasts in colour even within this limited range. In most installations, mono-chromatic sources should be used with great care. See Plate 5.

3.1.1 1 Day-time and There is a marked difference between the daylit appearance of landscapes and buildings and their appearance when artificially lit. There is a different order of contrast of objects seen against the black canvas of night compared to the light sky of day-time, whilst the relationships within a view can be varied at night by lighting selectively. The general direction and distribution of light are different, so there will be variation with the direction of view and the direction of the main flow of light.

night-time appearance

Lighting equipment when not concealed must be acceptable as part of the scene by daylight. For example, on occasions this may influence the spacing and height of posts to maintain the scale and visual quality of the environment, or the decision to mount fittings on facades in order to dispense with posts which may be intrusive.

3.2 Functional considerations

3.2.1 Brief

3.2.2 Site surveys

A clear brief should be developed which takes into account all aspects of a project both aesthetically and functionally. The aims and objectives should be agreed and standards set by reference to known examples and to recommendations in statutory or guidance documents, as well as discussions with recognised authorities or interested groups. Functional considerations may include matters related to traffk, humanistic considerations such as light pollution, safety and the feeling of security; or appropriate lighting for specific activities such as sporting events. The establishment of an appropriate quality of visual environment is just as important a requirement as the provision of an adequate quantity of light to enable a particular activity to be carried out.

Approaches to and sites of proposed exterior lighting installations should be surveyed to establish the factors which may condition the design. The aesthetic qualities of the surroundings should be carefully considered. These may range from the hierarchy of viewpoints and of principal features to the identification of hazards. Colours, reflectances’and textures of main elements should be recorded and note taken of the general night-time brightness of the area. The location and adequacy of rhe power supply must

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3.2.3 District brightness

3.2.4 M a in te nance

3.3 Factors affecting the visual environment

3.3.1 Illuminance

3.3.2 Reflectance

3.3.3 luminance and brightness

be established and possible accessible sites for equipment and for cable routes should be noted. In order to use favourable sites and routes way- leaves may have to be obtained and in some cases approval may be needed in the case of ancient monuments or listed buildings. Proposals should be discussed at an early stage with the local planning officer who will give advice as to whether a formal planning application is required, or whether other permissions from interested parties may be needed, due to proximity of airports, main highways or navigable waters.

The degree to which an object is accentuated depends upon the contrast between the object and its background. To achieve a desired emphasis the luminance of the object has to be related to the district brightness. For example, a country church may need little more than moonlight levels to make its presence felt whereas a building lit to this level in the centre of London would hardly be noticed. The three main bands of district brightness are rural, suburban and town or city centres. Illuminance levels for this range of district brightness areas are given in Table A1 .l.

Good maintenance avoids wasting energy, prevents deterioration of equipment, helps to ensure safety, and keeps the performance of the lighting system within design limits. A high proportion of the light emitted by a luminaire will be absorbed by dirt deposited upon it. Ease of access for maintenance is essential together with the provision of suitable hard standings for vehicles or ladders in landscape situations if maintenance operations are to be carried out effectively. Recommended procedures are described in Section 7.

Illuminance is a measure of the amount of light falling onto a surface. The ability to judge absolute values of illuminance by the human eye is greatly inferior to our ability to judge reflectance.

Reflectance is the ratio of the light reflected from a surface to that incident upon it. It can be assessed visually with moderate accuracy. The reflectances of some common building materials are given in Table A1 . 1.

Luminance is sometimes referred to as brightness, but there is no simple relationship between the two. Brightness is used to describe our perception of the luminosity of an object or how much light a source appears to be emitting in our direction. Brightness cannot be measured but luminance can. Luminance is the measurable amount of light emitted by a source or surface per unit area in a given direction. The luminance of a reasonably matt surface is approximately proportional to the reflectance of the surface, and is generally independent of the direction of view. For smooth, shiny surfaces the luminance is dependent on the direction of the source and view.

A dark coloured surface that is well lit may have the same luminance as another surface of higher reflectance which is receiving less light, but in normal conditions of viewing the two surfaces will not look the same. The designer may generally find it more helpful to think in terms of the brightness of surfaces of known colour, rather than in terms of luminance alone. In particular, the designer is likely to find it helpful to think of the effects it is wished to achieve by considering which parts of the scene or picture should appear very bright, and which less so.

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3.3.4 Glare

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Glare is the result of excessive contrasts of luminance in the field of view. The effect may vary from mild discomfort to an actual impairment of the ability to see. This is usually caused by viewing a bright source against a dark background. The creation of an interesting lighting effect involving marked contrasts in the scene, for instance lighting part of a building very brightly and leaving the rest in comparative shadow, rarely causes glare.

Direct glare from lighting equipment can be restricted in several ways. The techniques commonly used include careful positioning and aiming of floodlights and other sources of high luminous intensity. The use of hoods, spill rings and louvres for screening lamps from sight at normal viewing angles are often used but these will reduce the photometric efficiency of the lighting system.

Specific applications

Each ‘specific application’ details in tabular form the area/location or task where a maintained illuminance is recommended. There may be circumstances which would lead the designer to use a higher illuminance than that recommended. Unless stated otherwise the maintained illuminances refer to a horizontal plane at ground level.

4.1 Shopping Area, Maintained Notes location, illuminance or task (lux)

precincts and pedestrian areas

Open pavement 20 1.5 m above ground (minlave >0.3). Vertical illuminance 15 lux.

Covered pavements, 75 Vertical 1.5 m above ground. overhangs and steps

The table of illuminances recommends both vcrtical and horizontal illuminances at 1.5 m to ensurc that facial expressions are easily recognised so that pedestrians feel secure.

The emergence of modern outdoor shopping precincts has been an indication of the strength of demand for an increased concentration of city retail and commercial business.

Planning authorities, anxious to secure busy and prosperous city centres have realised the benefits of improved traffic circulation systems, car parking facilities and pedestrian traffic segregation.

The major retail shops and stores have virtually re-grouped to form extensive shopping areas which are accessed from a main thoroughfare, square or walkway. The area is usually traffic free, predominantly open to the sky, but may be connected to the neighbouring streets by covered linkways and circulation spaces.

Lighting equipment should be chosen which is in keeping with the public nature of the area. An impression of brightness, warmth and unity is desirable, particularly throughout the circulation spaces. Colour should be recognisably natural and people pleasantly modelled and not inconvenienced by glare.

Light, safety and security are required in all parts of the precinct but where there are hazards such as steps and escalators, or seating areas and other focal points the illuminance should be increased. Such areas of higher ambient illuminance introduce variety to the scene and further interest is added if flower displays, shrubs, advertising bollards, trees and other

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3.3.4 Glare

4

Glare is the result of excessive contrasts of luminance in the field of view. The effect may vary from mild discomfort to an actual impairment of the ability to see. This is usually caused by viewing a bright source against a dark background. The creation of an interesting lighting effect involving marked contrasts in the scene, for instance lighting part of a building very brightly and leaving the rest in comparative shadow, rarely causes glare.

Direct glare from lighting equipment can be restricted in several ways. The techniques commonly used include careful positioning and aiming of floodlights and other sources of high luminous intensity. The use of hoods, spill rings and louvres for screening lamps from sight at normal viewing angles are often used but these will reduce the photometric efficiency of the lighting system.

Specific applications

Each ‘specific application’ details in tabular form the area/location or task where a maintained illuminance is recommended. There may be circumstances which would lead the designer to use a higher illuminance than that recommended. Unless stated otherwise the maintained illuminances refer to a horizontal plane at ground level.

4.1 Shopping Area, Maintained Notes location, illuminance or task (lux)

precincts and pedestrian areas

Open pavement 20 1.5 m above ground (minlave >0.3). Vertical illuminance 15 lux.

Covered pavements, 75 Vertical 1.5 m above ground. overhangs and steps

The table of illuminances recommends both vcrtical and horizontal illuminances at 1.5 m to ensurc that facial expressions are easily recognised so that pedestrians feel secure.

The emergence of modern outdoor shopping precincts has been an indication of the strength of demand for an increased concentration of city retail and commercial business.

Planning authorities, anxious to secure busy and prosperous city centres have realised the benefits of improved traffic circulation systems, car parking facilities and pedestrian traffic segregation.

The major retail shops and stores have virtually re-grouped to form extensive shopping areas which are accessed from a main thoroughfare, square or walkway. The area is usually traffic free, predominantly open to the sky, but may be connected to the neighbouring streets by covered linkways and circulation spaces.

Lighting equipment should be chosen which is in keeping with the public nature of the area. An impression of brightness, warmth and unity is desirable, particularly throughout the circulation spaces. Colour should be recognisably natural and people pleasantly modelled and not inconvenienced by glare.

Light, safety and security are required in all parts of the precinct but where there are hazards such as steps and escalators, or seating areas and other focal points the illuminance should be increased. Such areas of higher ambient illuminance introduce variety to the scene and further interest is added if flower displays, shrubs, advertising bollards, trees and other

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appropriate features are designed to receive emphatic lighting. See plates 6 and 7.

The night-time appearance of a precinct is affected considerably by the type of luminaire and equipment used. The designer should consider the psychological impact of the space and design accordingly. Unobtrusive systems are desirable in some precincts, whereas in others the luminaires and columns can be used to enhance and extend the visual impression of the space by being a feature of the scene both by day and night.

Consultation with any private security company employed by the authority and also with the local crime prevention officer will reveal any particular problems of vandalism and anti-social behaviour likely to affect the choice of equipment and its installation. There will be areas where fortuitous light provided by spill light from shop windows will not be available after certain hours when the shops are closed; areas that may appear well lit during normal business hours may need a lighting scheme for the hours after closing. In traffic-free precincts the visual requirements of the motorist are no longer important. However, main road street lighting lanterns may still be considered appropriate for they can be efficient and unobtrusive, particularly if they can be mounted on short outreach brackets on the facade of the precinct buildings. If floodlight projectors are used, mounting height, lateral spacing and aiming directions should be chosen with extreme care in order to restrict glare, prevent the formation of deep shadows and provide the desired illuminance and uniformity.

Small decorazive lanterns on 5-6 m columns are often acceptabIe but the larger the floodlight and lantern and the higher the supporting column, the more obtrusive the system becomes and the scale of the entire precinct architecture may be in jeopardy.

4.2 Covered precincts Area, Maintained Notes location, illuminance or task (lux)

and arcades

Circulation areas 75 Vertical 1.5 m above ground. Entrances 75 After dark, as above.

~ ~

The reason for vertical illuminance at 1.5m is so that pcople can recognise the expressions of others so that they can feel safe and secure.

Many traditional shopping arcades have glass roofs which admit daylight to create a pleasantly bright environment. Lighting at night time is usually by decorative pendants or wall mounted luminaires that provide, in conjunction with spill light from the shop windows, adequate illuminance for safe movement and a pleasantly bright environment. A modern covered shopping precinct or arcade may be part of a large building and may even be integrated with office complexes.

The roof is generally designed to provide liberal quantities of daylight around the central areas. Elsewhere individual rooflights are sometimes incorporated into the building at carefully chosen points.

In many interiors apart from skylight views there is generalIy no direct visual contact with the world outside. Therefore, the lighting has to be designed with care and often as a transition from daylighting to artificial lighting. Large numbers of people are often present and the problems for the lighting designer are usualIy those of ensuring interest and variety and avoiding monotony.

The illuminance should be adequate for safe movement in all parts of the space whilst glare should be restricted to an acceptable level. Provided that

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colour rendering is good, either 'warm' or 'cool' lighting is suitable for covered precincts. Warmth is generally provided by shop and display lighting and so the introduction of metal halide into the circulation areas can provide a cooler balance.

Escalators and stairways should receive adequate lighting. Emergency lighting should comply with the requirements of BS5266 Code of practice for the emergency lighting of premises"' with consultation with the local authority.

A ceiling reflectance of at least 0.6 and wall reflectances of 0.3-0.5 are desirable. The limiting glare index in all circulation areas should be no greater than 22.

Tubular fluorescent, metal halide, high pressure mercury and high pressure sodium provide suitable lighting systems in circulation zones. Halogen lamps provide better operating life than standard incandescent lamps and are excellent for accent lighting with good colour.

Ceiling-mounted or recessed luminaires with a relatively wide light distribution provide pleasant modelling and this can be augmented by non- uniform patterns of light provided by discharge lamps either indirectly with sources concealed or as direct downlighting.

4.3 Business parks Area, location, or task Maintained Notes illuminance (W

Security 20 See Section 5.5. Road and pathway 5 See Sections 4.14,4.15, and 4.16. Building SCC Scction 5.3. Landscape

and commercial zones

See Sections 4.16, and 5.7.

As the number of business parks and commercial zones of green field sites increase due to a growth in demand for this type of accommodation, the sites themselves are evolving in terms of their character. The lure of attractive hi-tech buildings set in well designed landscaping is influencing the number of prestige organisations wishing to re-locate. This places greater responsibility upon those who may influence the quality of the night-time rural environment. Some parks now extend over a substantial amount of semi-rural area and they present varied visual requirements that need to be brought together into an integrated whole.

The successful lighting for an area like this integrates these features into a coherent whole. There can be a tendency for the street lighting, security lighting and floodlighting to be done by separate people often without reference to each other; to realise the full potential of the night time scene co-operation should be encouraged.

4.3.1 Security lighting This is essential in an area that is tempting to burglars and vandals and that tends to be unoccupied at night. Much security lighting will be achieved by good street lighting as long as it is borne in mind that back alleys should also be adequately lit. Perimeter lighting is important for security. Perimeter fences and walls should be lit together with the spaces between them and the buildings. The walls of the buildings should be lit so that people are seen in silhouette against them or with their shadows projected onto the building facade. This can often be combined with building floodlighting. Security lighting is dealt with in detail in Section 5.5.

4.3.2 Road lighting Road lighting contributes an enormous amount to the appearance of the area so it is often an advantage to use attractive luminaires for street

9


lighting. This can only be done within street lighting regulations but where possible the appearance from a distance should be borne in mind. Pathway lighting in parks and gardens is dealt with in Section 4.16.

4.3.3 Building floodlighting Many commercial companies are conscious of their image to the outside world and find floodlighting a good way of projecting this image. On green field business parks the use of floodlighting can be an excellent way of creating an active image for the whole area by night. Building floodlighting techniques are dealt with in Section 5.3.

4.3.4 Park lighting

4.4 Vehicle

There is an increasing tendency for commercial companies to project a green image that shows their concern for the environment. Trees, shrubs and other landscape elements are used as settings for the building. An interesting perspective can be created if these features are lit at night, both to bring them out in their own right and to integrate them with the buildings they relate to. Park and garden lighting is dealt with in Section 4.16.

parks Area, Maintaincd Notes location, illuminance or task (lux)

Surface car parks Ground (public) 20 Ground (private) 10

Column height may vary berween 3 m and 12 m. Height used should be kept in scale with surroundings.

Muhi-storey und underground car parks General areas 50

intersections Kamps, corners, and 75

Stairways I00 Open roofs 20

Lorry parks Low risk - normal parking 20 High risk - normal parking 30 Loading and unloading 50

There are two main types of public car park used by the public: open air surface parks and covered multi-storey or underground parks. The lighting systems used for the two types would of necessity be different but their purpose is the same, to provide for the visual security and physical safety of those who use the area. This can be achieved by providing general lighting that clearly reveals cars and pedestrians, enables empty parking bays to be detected easily, and assists site supervision and security. Supplementary lighting may be required at automatic entry and exit equipment so that instruction notices can be read easily from the driving seat, and also at ticket machines, ticket collection and payment points. Suitable lighting is also necessary on the stairways of multi-storey car parks.

4.4.1 Surface car parks An illuminance of 20 lux, measured horizontally at ground level, is recommended for large public space car parks and may be provided by floodlights, road lanterns or post top lanterns mounted on suitable columns. Private car parking needs to give a feeling of security in the space and in these areas 10 lux is adequate. The style of lighting will set the scene. Ideally columns should be positioned around the perimeter of the park where they are least likely to be damaged by vehicles. The layout of columns and floodlights around the perimeter is easily determined if it is assumed that wide angle floodlights will provide useful illuminance over a depth of area equal to three times their mounting height, and that lateral spacing between floodlights should also equal about three times the mounting height. These ratios are called the ‘rule of three’. This method is detailed in Section 5 and Appendix 1.

10


Figure 4.1 Typical lighting layout for surface car park asymmetrical or double asymmetrical floodlights mounted on 8-12 m columns spaced around the perimeter.

4.4.2 Multi-storey and underground car parks

The selected column height will often have to be a compromise. It needs to be high enough to ensure the floodlights are well above parked vehicles, which create increasing lengths of shadow as their distance from the floodlight position increases, and to minimise glare for drivers using the car park. However, the height must be related sensibly to the height of nearby buildings and it may well be limited by Local Authority Bye-Laws. Maintenance of any floodlighting system mounted at heights over 8 m should be taken into consideration.

If it becomes clear that the column height required is excessive an alternative solution may be to use intermediate columns, effectively splitting the car park into two, using symmetrical distribution lanterns on lower columns in a regular array based on a spacing to height ratio of about 4: 1. Such an installation may prove less economical and less efficient but it is also likely to have a less severe and more aesthetically pleasing appearance. See Plate 8.

Luminaires used in these locations need to be suitable for installation in semi-exposed weather conditions and may need to be sufficiently robust to withstand the attention of vandals. These requirements dictate the use of enclosed luminaires which, in the interests of economy, should use high pressure discharge lamps or fluorescent lamps; colour recognition is important so low pressure sodium lamps should not be used. Glass fibre reinforced plastic or aluminium luminaires with high impact acrylic or polycarbonate, gasketed enclosures will prove the most satisfactory in the climatic conditions and corrosive atmosphere created by vehicle exhausts. In underground car parks, local bye-laws may demand that luminaires suitable for hazardous areas are used.

The transition zone at entrances and exits needs special consideration to assist the adaptation of the eye, particularly during daylight hours, the illuminance at these points should be greater than that within the car park. The perimeter walls and rails of open deck multi-storey car parks should be adequately illuminated to define the boundary. The lighting installation should clearly illuminate the correct circulation route along each level and the way from one level to the next. Luminaires should be sited at each route intersection so that these areas are illuminated to a higher level than the average illuminance of the whole area.

Luminaires may be mounted over the circulation routes but because ceilings are usually low they could be near to the driver’s line of sight. This could produce glare which will make it difficult to see pedestrians moving between vehicles or to quickly locate an empty parking bay. Glare may be restricted by using low brightness or shielded luminaires, or by making use of roof beams to screen the lamps from view at normal angles. When un- screened fluorescent sources are used these should be mounted in the direction of traffic flow. Because vehicles will be, or should be, moving slowly, a uniformity of 0.05 will be adequate.

Stairways should be lit as described in Section 4.13.

Direction - of travel Figure 4.2 Lighting systems for multi-storey

and basement car parks with luminaires shielded by roof bcams.

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4.4.3 lorry parks Often storage car parks and large lorry parking areas contain valuable stock and items in transit. Therefore there is a need to consider aspects of security in addition to safety and movement.

Generally lorry parks are most satisfactorily lit from the perimeter of the area to reduce the risk of damage to columns or floodlights which may be caused by large vehicles manoeuvring in a confined area. If this is not practical crash barriers should be used to enclose and protect island mounted columns. The inherent size and bulk of lorries means these floodlights should be mounted at least 12 m from the ground to reduce the shadowing effects, which will be far greater than in a car park. There are clear economies to be gained from using a fewer number of high columns, each supporting several floodlights rather than a greater number of low columns with individual luminaires. High columns also allow the use of high wattage floodlights that would produce disability glare if used at lower heights.

The height of columns required can be calculated by using the 'rule of three' described in the preceding Section 4.4. I . It should also be noted that it is usually both glaring and inefficient to aim floodlights at angles greater than 7 5 O from the downward vertical. However, the exact choice may be influenced by economic advantages of fixing luminaires to the walls of adjacent buildings, maintenance difficulties or local planning requirements.

Maintenance aspects should be carefully considered. There are several types of columns and masts available. Some have headframe assemblies that can be lowered, others have a hinge arrangement that allows the whole column to be lowered to the ground. Alternatively the column may be a fixed type requiring access from a tower truck, or perhaps be of the high mast variety with built-in climbing facilities. Whatever is used, luminaire and lamp reliability will be of paramount importance. Discharge lamps will prove the most economical to operate, and will provide long lamp life. In practice high pressure sodium lamps are likely to prove the most suitable having longer life and higher efficacy than comparable mercury lamps.

4.5 Outdoor work Arca, Maintained Notes

and storage location, or task

illuminance (lux)

Safety/amenity 10 Horizontal. Storage areas 20 Horizontal Walkways and platforms 50 Horizontal

Dcpcnding on th type of work or storage, vertical illuminance may be more important. If this is so the same values should be taken.

Over half of all Industrial premises have an exterior area where outdoor work is carried out or where goods or equipment are stored. Specific recommendations are detailed in the CIBSE Lighting Guide: The industrial environment(2' and CIBSE Lighting Guide: Building and civil engineering sites' ". Many industries use production processes or have fabrication and storage requirements that necessarily have to be totally in open space. Typical of these are shipbuilding and repair, dockyards, ports, container terminals, petrochemical plants, building and construction, horticulture and agriculture.

Premises associated with light industry more often than not are to be found on urban trading estates, a large proportion not being constructed specifically for the eventual occupier.

Such developments, particularly the more recent business parks, usually offer relatively generous exterior areas and if these are not utilised for work

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4.5.1 low mounted systems (8-15 m)

4.5.2 High mounted systems (1 5-60 m)

processes they will most certainly be used for storage of some kind, parking of vehicles and access and will require light after dark for these requirements as well as for night-time security.

Whatever the main lighting requirement it is important that the installation be designed to be energy and visually effective, For those industries where visual tasks are demanding and illuminances need to be of the higher value, the lighting must meet the safety needs of the workers. Primarily this means ensuring that the lighting system does not in itself create additional hazards to workers by producing glare and areas of excessive contrast which could confuse and disable vision.

In this context the designer must ensure that glare is well controlled and that recommended uniformity ratios are achieved to avoid areas of excessive brightness. Once these principal objectives have been satisfied the installation must be well commissioned to ensure that luminaires are aimed and focused correctly. The lighting system must not create areas of shadow which could conceal unseen hazards.

There are two basic forms of lighting outdoor work areas, and both use a generally downward distribution of light. However, on occasion, detail on the vertical surfaces may have to be seen from a distance and lit accordingly. The identification of labels in storage areas and the more demanding tasks of reading dials and valve gauges on the vertical plane may require forms of supplementary illumination.

In this type of system projector floodlights with wide distributions or even appropriate street lighting lanterns can be satisfactory, providing the most efficient type of lamp possible is utilised. It is more economical to employ a number of high wattage lamps at the greater mounting height. Generally, the sideways spacing of support columns or poles should not exceed 3:1 although if it is required to achieve an improved performance of diversity this may be reduced to 1.5: I .

Every part of the area should receive a proportion of light from two directions but if this is not possible the depth of the effective lighted area should not be more than 5 times the height of the luminaire above ground.

If two-directional lighting can be achieved by placing additional columns it may be practical to extend the ratio to 7: 1. Any decision on the final choice of the mounting height must be made after considering the degree of uniformity required, the ease of attaching luminaires and equipment to structures or buildings, whether the area is free from obstructions or not, ease of maintenance and possible constraints placed upon the installation by any requirements to comply with local planning.

Typical reasons for considering the use of high mast and high tower systems would be: a very large open area; greater like4ihood of damage to a more conventional installation; a greater problem of glare from the lighting; and a large proportion of obstruction in the area.

If it is necessary to light an area from one side only it would be good practice to mount the floodlight projector luminaires as high as practical, up to 30 m above ground, ensuring that the depth of light throw does not exceed a ratio of 51.

If it is possible to utilise high towers of 30-60 m incorporating a head-frame from which floodlights may be aimed in all directions. A spacing to mounting height ratio of 7:l will be satisfactory provided all parts of the area receive light from at least two towers. Often the choice of the equipment most appropriate can be made from detailed consideration of

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the constraints imposed by the site environment and its layout. There is often the possibility of utilising conventional lighting equipment in an unconventional manner and this can avoid the designer having to involve special or non-standard equipment at high cost.

4.6 Railwav and Area, Maintained Notes location, illuminance or task (lux)

coach s’tations

Concourse 200 Horizontal, uniformity ratio should not be less

Printed timetable 200 Vertical, local lighting system. Platform 10 Horizontal, care should be taken to light and

identify the edge of the platform clearly. Ensurc reflected glare is not evident on VDU

information monitors. Horizontal, localised lighting is likely to be necessary.

than 0.2.

Coach loading areas 150

Railway and coach station concourses are busy places and good lighting assists the safe and rapid movement of passengers and luggage, creates a cheerful atmosphere in seating areas, minimises the risk of accidents on crowded escalators, travelators and stairs and helps timetables and notice boards to be easily read. Kerbs should be clearly visible, so that drivers are able to see passengers on the lanes without using headlights, and confusing shadows cast by parked and moving vehicles minimised. Coaches generally park close together so care should be taken to light between the coaches.

Concourses with a high roof can be lit efficiently by high pressure sodium, mercury fluorescent or metal halide lamps in concentrating reflectors which are suspended from the roof and direct 10-20% of the light upwards. If the roof is painted in a pale colour the light reflected from it will soften the harsh shadows produced by direct lighting systems of this type. The increase in restoration, renovation and cleaning of large vaulted roofs has stimulated interest in lighting these to reveal their qualities. The atmosphere and appearance can be enhanced by lighting these roofs particularly from luminaires concealed along the edges and projecting their light into and along the trusses. The lighting of concourse restaurants, bookstalls and similar features should be treated as part of the total lighting scheme.

Where possible, provision should be made for servicing the lighting equipment from the roof, or from behind the ceiling, to avoid inconvenience to passengers and staff. If equipment is accessible only from the concourse the frequency of maintenance can be reduced by using lamps with a nominal life of at least 6000 hours and luminaires that are either self- cleaning or dust-proof. See Plate 9.

4.7 Hospitals and Arca, Maintained Notes location, illuminance or task (lux)

health care

Roadway Car parks

5 BS 5489 Code ojprucfice for roud lighting‘4’. 10 See Section 4.4.

Access routes, linkways 15 Vertical, 1.5 m abovc ground. Signs 100 Vertical

The exterior lighting for hospitals and health care buildings is required to fulfil three functions: amenity, safety and security.

Consideration should be given to safety and security aspects of exterior lighting and to providing a welcoming environment. In some cases, the use

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4.7.1 Signs

4.7.2 Roads

4.7.3 Car parks

4.7.4 Paths

of monochromatic, low pressure sodium sources gives rise to a feeling of insecurity, These factors should be taken into account when selecting light sources.

The choice of locations for direction signs is based primarily on their use in daytime. However, if practicable, they should be located so that they are clearly illuminated when the road lighting is in use. Preferably, the road lighting should be planned to light the signs as well as the roadways. Internally illuminated signs are not recommended because they are liable to damage and require frequent servicing.

Local lighting by external luminaires must be sufficiently uniform for signs to be read easily and should be used only when the road lighting installation is inadequate for this purpose.

Road lighting installations conforming to categories as defined in BS 5489: Part 3, Lighting for subsidiary roads(4’, are generally adequate for all roadways around the hospital complex. The amount of light should be compatible with that on adjacent public roads which may have Category 1, 2 or 3 installations.

Consideration should be given to the use of lighting for hospital roads used by public vehicles or having a traffic flow exceeding 400 vehicles per hour. Some grading of the illuminance levels may be desirable to avoid sharp contrasts between the category levels.

Car parks vary considerably in size from small staff car parks at health centres to main hospital car parks. Peripheral lighting attached to the adjacent buildings is suitable for smaller car parks but for larger car parks floodlighting using high output low energy sources is more suitable. See Section 4.4.1.

Footways and pedestrian walkways that are not well lit from adjacent roads or from the lights in adjacent buildings require their own lighting. This should be preferably by wall-mounted lanterns providing good vertical illumination, or from bollards about l m high, but these do not provide a sense of safety as they only light the route, not peoples faces. Low level lanterns should be vandal resistant.

4.7.5 Other considerations Routes to plant rooms, at either ground or roof level, should be well lit for the safety of maintenance staff.

The siting of external light sources requires careful consideration to avoid stray light entering wards and staff bedrooms. Lanterns should be fixed to suitable external surfaces of buildings wherever possible. Lanterns should not be located near trees which may cause disturbing flickering shadow patterns in bedrooms.

For on-site security, all areas should be adequately lit but particular consideration should be given to industrial zones, pharmacy drug stores and residential accommodation. There should be no areas of darkness that may encourage unauthorised persons to gain access to or linger in the hospital grounds.

15

ClBSE LIGHTING GUIDE

4.8 Banks and Area, Maintained Notes

or task illuminance (lux)

b u i Idi ng societies location,

4.9 Educational precincts

Facades, signs 100 Vertical, see Section 5.3. Entrances, exits, auto-bank 50 points Walkways, security lighting 20 See Section 5.5. Car parking 10 See Section 4.4.

Night-time lighting for the building exterior must be considered mainly with the requirements of security in mind, but the appearance of the completed installation must not be one that seems security motivated.

It is important that people using the auto-bank facility at night-time should feel as safe as possible. Where auto-banks are recessed into the facade, locally positioned lighting may be required to increase the illuminance and remove any dark shadows.

Facade and feature lighting to emphasise the character of the building may be applied in a similar manner to any other important high street business. The lighting must be tasteful and any use of colour carefully considered. Entrances, particularly if recessed, exits and auto-bank facilities, particularly if on a side road or where there may be a lack of good street lighting, should be well lit. This is not necessarily to prevent intrusion but to deter vandalism and criminal damage. If the premises are enclosed at the rear by a solid perimeter which provides natural concealment, all this area should be well and uniformly illuminated, in addition to emphasise lighting on access points, entrances, exits, first storey windows and ledges, and on any obvious route that an intruder may use to gain access to the roof. If skylights are a feature of the roof area these should be externally lit if practical, providing measures have not been taken to inhibit access to the roof.

Facade and feature lighting may be adequately controlled by solar dial time switches, with management deciding on the operating hours. Luminaires which provide the security aspects of the lighting may be better controlled by photo electric sensors or passive infra-red sensors which detect movement. In these instances, particularly at entrances and exits, it is recommended that should the sensing device fail the controlling circuit will remain energised and the illumination will continue to be provided.

Area, Maintained Notes location, illuminance or task (lux)

Roadways, general movement 5 See Section 4.14. Car parking area, bicycle racks 10 See Section 4.4. Walkways, pcrirneter zones, 20 See Appendix 1 . security Facadcs and signs 100 Vertical. Recreational and club sports 100 Notice boards 150 Vertical.

Universities, colleges and schools often occupy prominent sites in both city centres and residential districts and can cover extensive areas, often incorporating housing and residential accommodation.

Requirements for exterior lighting can be many and varied. I t is necessary to consider outdoor lighting in terms of several distinct requirements. Lighting has to be provided for access on roads and pathways, for security to deter break-ins, vandalism and personal attack, for after-dark sports activities and for the benefit and prestige provided from the relatively small-scale floodlighting of certain historic or important buildings and features,

16


4.10 Commnity buildings

Wherever possible luminaires should be mounted sufficiently high to be beyond normal reach and should be of a sturdy construction. While satisfying the requirements of vandal-resistant lighting, care must be taken to avoid an institutional appearance, for this reason many installations have utilised a decorative post top lantern.

Improving the decorative aspects of many of these types of buildings will be largely achieved by the provision of suitable and adequate amenity and security lighting, and lighting to emphasise architectural features may need only to be supplemental.

Due to the usually close proximity of buildings to each other in schools and colleges floodlighting of facades with excellent modelling is possible because of the availability of buildings and roofs upon which luminaires can be mounted. By illuminating a number of adjacent building facades the use of columns or poles can be reduced so as to minimise the electrical installation costs.

Floodlighting from one building to another can often eliminate the glare which may accompany a floodlighting system where luminaires mounted on a building are aimed outwards to illuminate adjacent areas.

If luminaires are roof or parapet mounted care should be taken to ensure that access to the roof is only to authorised maintenance staff thus eliminating problems of vandalism.

Free-standing bollards which use high pressure discharge sources are especially suited to the identification of hazards and steps. The use of walls or supporting structures which would be capable of accepting and concealing luminaires would provide excellent orientation lighting and reduce both glare and maintenance problems.

External signs and notice boards may require lighting independently. The use of energy saving compact fluorescent lamps should be considered: available in vandal resistant versions, in addition to their low energy consumption, their low maintenance costs can play an important role.

These luminaires are ideally suitable for lighting under-cover bicycle stands and should be spaced about 4 m apart.

Area, Maintained Notes location, illuminance or task (W Pathways, main access 10 Pathways, secondary 5 Car park area 10 See Section 4.4. Notice boards 150 Entrance porch 200

The importance of local community and church halls in the social life of any community cannot be underestimated, and this valuable role should be made more evident at night-time by the attention paid to appropriate exterior lighting.

The exterior lighting system should help to identify the facility and create a favourable and welcoming impression. This is particularly important for the mid-winter period when community halls are generally in greatest use.

The lighting should provide for the safety and welfare of visitors and property, especially in any car parking areas and along the paths around the building. I t is essential that people attending the premises should feel safe

17


and secure. The lighting should illuminate particularly dark areas and avoid threatening shadows which may easily conceal steps or confuse, and which may otherwise invite vandalism or pose problems in terms of personal security. If the building and grounds are generously surrounded by trees and bushes, it is necessary to ensure that good lighting is present particularly if there is an absence of roadway lighting. The main approach path and entrance porchway should be well lighted. If floodlighting is to be installed it is important not to locate luminaires immediately in front of the porch steps which may cause confusing glare to people leaving the premises. Consideration should be given to the column of the road lighting in use and its location when deciding on the floodlighting effect required. Usually the most effective results will be achieved by floodlighting small areas of the building and these will have a greater visual impact providing adjacent street lighting does not conflict with the overall image.

4.1 1 Hotels, motels Area, Maintained Notes and restaurants location, illuminance

or task (lux)

Car parking 10 See Section 4.4. Delivery, rubbish and refuse 30 Steps, hazards 50 Walkways, pathways 10 See Section 4.13. Undcr canopy 100

The access points for hotels which are adjacent to busy main roads that carry fast traffic should be made easily identifiable to the approaching motorist so that a safe turn may be made from the traffic flow into the driveway or car park.

The lighting of the prominent faces of the building and adjacent grounds, which are visible to the road can create an impression of cheerfulness and welcome. Although some Iuminaire brightness may be considered attractive care must be taken to ensure that the type of luminaire or directional aiming does not create glare which would interfere with passing vehicles, or the vision of drivers as they leave the main road and enter the parking areas.

Good lighting is necessary for good housekeeping and to enable evidence of unacceptable practices and dirty waste to be readily seen. Access, assembly points, corners and peripheral areas should also be lit well for safety during emergency conditions, such as fires, as well as promoting cleanliness and hygiene.

Lighting of the building facade, walkways to the entrance, under canopy and car park should be co-ordinated with any advertising on direction signs to produce a coherent and harmonious impression.

Entrances to fast food drive-in establishments should be so well lit as to appear prominent to the driver of a vehicle. As this type of establishment is likely to display relatively large illuminated signs it is important to ensure the lighting installation be used to provide orientation and to emphasise the intended traffic patterns.

The agreement of the local authority may have to be obtained before any lighting is installed, or signs erected, at entrances leading from or to a public highway.

18


4.12 Garage forecou rts


Approach apron, general 50 access to forecourt Forecourt, pump areas 300 Illuminance should provide for adequate

under-bonnet illumination. Glare must be avoided. Seek local Petrolcum Officers’ approval.

The general layout of a typical service station consists of an open forecourt with entrance and exit and with an arrangement of petrol and diesel pumps, on island plots, usually beneath an overall canopy to provide weather protection. The primary function of a service station is to provide petrol, but a service station shop has become an important source of turnover and profit over and above the revenue from petrol sales.

The main objective to be considered in designing service station lighting is the identification of the product, brand services offered and facilities available. How well it is lit and the quality of the signs will combine to give the driver adequate time to reduce speed and manoeuvre into the correct position to enter the forecourt, and permit the driver to judge quickly the standard of the station.

The quick first impression is one in which good lighting and visual impact play a vital role. Although this is particularly relevant to night-time when the forecourt has to compete for the motorists’ attention with all the surrounding visual attractions so dominant in urban areas, such as shop window displays, neon signs, direction signs, public house floodlighting etc. it is equally relevant for the day-time. The location, legibility and luminance of the signs are primary factors for consideration. Signs should be located to facilitate advertising and identification from all practical approach angles.

The designer should ensure that the type of luminaires used on the canopy, pumps and approach do not conflict and do not distract from the advertising appeal of the main brand signs. There are three main functions for the lighting.

It must command the driver’s attention and provide safe entry into the forecourt.

It must identify the safe route the driver must take from the entrance to the pump island.

0 It must prominently illuminate the pump area and ensure that the island kerb is well defined.

Having satisfied the entry criteria the lighting must indicate to the driver where he must pay and enable him to drive away safely to return to the main road. The amount of light necessary to provide all these aspects of strong visual communication will depend to a large extent on the location of the service. station. Those situated in busy urban areas with high levels of competition will require a much stronger degree of emphasis than one in a remote rural setting.

The usual method of lighting is by utilising an overhead canopy structure. Luminaires may be affixed to the under-side of the canopy, or recessed into the canopy structure. An alternative method is to indirectly light the under- side of the canopy from floodlight luminaires mounted on the canopy support stanchions. In this method, basically an up-lighting application, the under-side of the structure should be matt-white and kept in a well maintained state. Utilising this method of indirect lighting from below the

19


canopy can make the installation and maintenance of the luminaires easier and ensures that only the minimum of weight has to be carried by the canopy itself. In attracting the attention of the passing motorist it is necessary to illuminate the forecourt in such a way that it will visibly stand out in contrast to the properties and areas which surround it. Care must be taken to ensure that signs, luminaires and their mounting height above ground are in scale and harmonise with the general environment and that any undesirable glare and spill light are well controlled and do not create annoyance to other road users and local residents.

4.1 3 Subways, Area, Maintained Notes location, illuminance or task (lux)

stairways and public footpaths

Subway Short 150 Ground. Long or complex 300 Ground.

Intersections and internal 300 Day and night. stairways Entrances 300 Daytime. Foot-bridgcs (open) 50 Open Stairways 50 Every effort should be made to illuminate the

risers differently from the treads, in ordcr to accentuate the steps.

Whatever form the access may take, a subway is a pedestrian tunnel and many of the parameters used by the designer to safeguard against inadequate lighting conditions in road tunnels may also be appropriate for subways of extended length.

The main lighting objective must be the safety and security of pedestrians and so should be inviting so as to reduce fear. It is important that lighting should reveal the presence of other people moving in the distance and be sufficient in quality and quantity to permit some facial recognition as pedestrians approach each other.

Some of the factors applicable to the specific problems associated with pedestrian safety and security need to be carefully evaluated. Particularly appropriate would be the type of property and land, which adjoins the subway and its usage. Reference may usefully be made to street crime experience and the security arrangements currently in force in the locality.

Subways, stairways and footbridges may give public access to precincts, parks and gardens, building interiors, city centre street crossings and underground coach and rail terminals. It is vital that there should be maintained minimum illuminances in the subway to deter loiterers and muggers.

In subways, care must be taken that vertical surfaces are well illuminated. All the surfaces should therefore be as light coloured as is practicable. The use of coloured signage on advertising posters can beneficially provide cheerful accents. These could usefully be of the internally back-lit type and recessed into the wall.

Subway luminaires should if possible be recessed into the wall or ceiling as surface mounted units are vulnerable to vandalism. The diffusers/ controllers should be of impact resistant material, such as toughened glass or polycarbonate, and fitted in frames secured to the luminaire body by vandal resistant fastenings. Care should be taken with the use of recessed ceiling-mounted luminaires which fail to provide sufficient illuminance on the ceiling surface; the subway may appear gloomy and give an impression

20


of reduced height. Cornice recessed or wall-mounted luminaires will solve this problem.

On longer complex subways emergency lighting systems using self- contained units and complying with the recommendations of BS 5266' ') should be considered.

Further guidance on the lighting of subways can be found in BS 5489 Part 9(4)

4.14 Roads and Area, Maintained Notes associated areas location,

or task illuminance (lux)

BS 548914' Part 3 Category 2 6

BS 5489'4J Part 3 Category 1 10 Minimum illuminance at a point 5 lux. Traffic use equivalent to that of a local distributor road or where there ia an active crime rare or high crime rate or cxtensive night-time public use. i.e. access to shopping facilities or othcr community amenities. Minimum illuminance at a point 2.5 lux. Traffic use equivalent to that of housing estate access roads or where there is an average crime risk or moderate public use after dark, this also may be associated with access to local amenities. Minimum illuminance at a point 1 lux. Traffic use equivalent to that of a residential area road or where crime risk is low or pedestrian usage at night-time is extremely low and associated solely with the adjacent residential property.

BS 5489''' Part 3 Category 3 3.5

When considering roadway lighting a number of fundamental factors need to be considered. Economy may be a concern but the success of roadway lighting installations is judged solely upon how well it fulfils its various functions. These are:

Lighting as a contribution to road safety and the reduction of night-time accidents. This applies in the main to those types of roads used by motor vehicles and other road users likely to be travelling at permitted speeds in excess of 30 mph. Lighting as a contribution to the maintenance of public order, safety and the prevention of crime. Associated areas such as shopping facilities and amenities which adjoin roads, residential and pedestrian areas are also to be considered. Lighting as a contribution to the quality of life in the community such as pedestrian amenity areas, business and recreational parks, and out-of town areas to be considered.

Economy of the installation in terms of initial and through life running costs.

Recommendations on the lighting of roads are provided by BS 5489'4'. This standard is divided into ten parts and gives general and quantitative guidance on lighting for road users, be they drivers or pedestrians.

Part I explains the general principles of road lighting and includes definitions of terms used in other parts of the standard. Part 2 is devoted specifically to the lighting of traffic routes and the recommendations are in terms of road surface luminance, uniformity, glare control and lighting of the pavements. The lighting of residential and subsidiary roads is covered

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in Part 3 (specific recommendations are given in Section 5.6). Here the emphasis is on the needs of the pedestrian and the recommendations are in terms of illuminance over road and footway areas.

The lighting of many complicated road layouts is explained in Part 4 (roundabouts and junctions) and Part 5 (grade separated junctions). Part 6 is concerned with the lighting of elevated roads as on bridges or viaducts. Because many such structures are landmarks, the overall visual impact of the lighting receives special emphasis. Two further parts of the standard deal with roads in particular situations: Part 7 with tunnels and underpasses and Part 8 and roads near airports, railways, docks and waterways.

Lighting for town and city centres and areas of civic importance is the concern of Part 9. Here, considerable emphasis is placed upon the amenity value of the lighting, as well as laying down minimum horizontal illuminance values required in various locations to give good visibility. Lighting-of motorways is dealt with in Part 10 and is based on the same premises as Part 2.

The nature of the lighting required depends on the usage of the particular road concerned. Where the road carries a considerable volume of traffic it is classified as a traffic route or main road and the lighting should be designed according to Part 2 of BS 5489‘4’. Three different categories of traffic route are defined as shown in the following table, each with a recommended value of average road surface luminance and overall and longitudinal uniformities. Glare criteria are expressed for various road categories. These criteria of performance are to ensure satisfactory visibility for drivers so that they can identify potential hazards and be confident of the direction of the road ahead. There is provision, too, in Part 2 of the standard for a proportion of the light to be directed onto the pavement for the benefit of pedestrians so that drivers have adequate warning of anyone about to step into the road.

Table 4.lRecommendcd values of luminance and uniformity ratio

Category Avcragc Ovcrall Longitudinal Examples luminance uniformity uniformity (cd/mz) ratio

2/ 1 I .5 0.4 0.7 High speed roads. Dual carriageway

212 1 .o 0.4 0.5 Important rural and urban traffic roads.

routes. Radial roads. District distributor roads BS 6100‘5’.

Local distributor roads ES 6100 Is’.

Residential area major access roads.

2/3 0.5 0.4 0.5 Connecting, less important roads.

Typical mounting heights for luminaires are 8, 10 or 12 my these being suitable for 90,135 and 180 W low pressure sodium lanterns or 70,150 and 250 W high pressure sodium lanterns respectively. Although the low pressure sodium lamps have the greater efficacy, they have a shorter life than the high pressure sodium, are monochromatic and are not as amenable to efficient optical design.

For the lighting of residential roads and subsidiary roads such as those in industrial sites, Part 3 of BS 5489‘4’ should be used. In this, the emphasis is on lighting for pedestrians, with lighting levels being specified in terms of average and minimum illuminances over road and pavement areas. Three categories of roads are defined according to their crime risk and pedestrian and traffic usage.

Typical mounting heights are 5-6 m for lower wattage low and high pressure sodium luminaires. Part 3 recommends the use of high pressure sodium lamps (SON) for those areas where the improved colour quality and

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colour rendering capability is likely to be particularly suitable such as those areas where pedestrian activities predominate, or where the crime risk is a factor to be considered, or which are environmentally sensitive.

The application of roadway lighting to factories and industrial sites is fully covered in CIBSE Lighting Guide: The Industrial Environment‘2’. It is however, likely that for simple roadway, footway and footpath lighting within industrial sites and factory areas where the speed of any motor vehicle is restricted to less than 30 mph, and such vehicles are equipped with the facility for dipped headlights, that Category 2/3 would be appropriate.

4.15 Tunnel This is a particularly difficult lighting problem and the reader should refer to BS 5489‘4’ Part 7. The primary objective of all vehicular tunnel illumination is the provision of optimum visibility both by day and night for the driver of the vehicle. The vehicle speed on entry may be as high as 70 mph and in conditions of heavy traffic flow spacing between vehicles may be as close as 15 m or less.

approaches and entrances

4.15.1 Tunnel zones

4.15.1.1 Threshold

4.15.1.2 Transition

4.15.1.3 Central

4.15.1.4 Exit

4.15.2 Night-time

4.1 5.3 Control

The luminance of the interior of the tunnel entrance is substantially less than that of the exterior so that the driver will only perceive the entrance area as a black hole. He will be unable to evaluate any detail inside the tunnel portal and it will be impossible for him to discern on his approach any obstructions there may be on the carriageway. The lighting level in the first part of the tunnel entrance, known as the threshold zone, is the key to dealing with this visual problem. It is dependent on the adaptation condition of the driver’s eyes and this may to a large extent be influenced by the luminances of the surroundings of the tunnel entrance. In practice the length of the threshold zone is likely to be 40-80 metres to coincide with vehicle speeds in the range 30-60 mph.

For relatively long tunnels it is possible to calculate an ideal luminance gradient to provide for a transition zone in which the driver would have some time for his eyes to adapt from daylight luminance.

The transition zone is usually followed by a zone in which the luminance level is constant. It should be noted that, depending on speed, adaptation may not necessarily be complete and it is necessary always to ensure a fairly high level of luminance. Evidence suggests that a minimum of 15 cd/m2 should be recommended for the average luminance of the carriageway in this zone. Considerably reduced speed limits would permit lower luminance values.

In the day-time the exit of a tunnel appears to a driver inside the tunnel as a bright hole against which any obstructions to his exit can be clearly seen in silhouette .

At night the criteria regarding lighting requirement is reversed. The level of luminance outside the tunnel is then lower than that inside and problems of ‘black hole effect’ may occur as the driver approaches the tunnel exit. Visual difficulties will not normally arise providing the ratio of the luminance level inside the tunnel to the level of the outside luminance at the tunnel approaches/exits is less than 3: 1 . The minimum night-time luminance should be 3 cd/m2.

To assist adaptation all approach roads should be illuminated for a minimum length of 200 m from each tunnel portal at entrance and exit.

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Such lighting must be in accordance with the recommendations of BS 5489‘4’. Dust and unburnt carbon deposited on the luminaires positioned within these stretches of carriageway by traffic passing through can seriously affect night time illuminances. This condition is unlikely to be met without a lighting control system designed to adjust interior luminances during the hours of darkness.

Supplemental lighting used in the various threshold and transitional zones to meet the requirements of day-time adaptation will have to be switched off, and all the remaining luminaires reduced by selective switching or automatic dimming. Care must be taken to ensure that any night-link dimming system installed should be as reliable in performance as is practicable in order to avoid lamp flicker effect.

Regular maintenance routines must be an essential part of any design specification.

Figure 4.3. Gatwick tunnel. The high illuminance in the threshold zone gives way to normal tunnel lighting which allows for visual adaption.

4.16 Parks and Area, Maintained Notes

gardens location, or task

illuminance (lux)

Main pathways 10 Secondary pathways 5

Focal points (large) 100 Focal points (small) 200

Steps 50 Trees/bushes 10

Outdoor sports See CIBSE Lighling Guide: Sportsf6’.

Public parks and gardens are pleasant and very desirable features of the community environment and are found in almost every city and suburban areas.

During the summer months there should be no sensible reason why the enjoyment associated with outdoor activities should not be continued long after darkness has fallen. Artificial lighting can extend the time during which the various amenities provided can be enjoyed. Lighting in certain areas of a park is essential for safety, especially of children at night-time: whilst the application of lighting also plays a major role in helping to deter many forms of anti-social behaviour in outdoor locations. It does not require extensive investment to extend this minimum lighting objective to the point where the installation is able to reveal the beauty of flower beds in full bloom, of trees, shrubs and water features in a highly attractive manner and helping to foster a feeling of communal pride and a sense of landscape perspective to the area.

The lighting of a park or garden involves the illumination of trees, shrubs, flower beds and, possibly, ponds and fountains which themselves may incorporate features like statues or small bridges which also could be attractively lit. The main objective being to accentuate the beauty of the general scene and to eliminate any dark shadowy areas that may detract from the visual impression or that may be considered a safety hazard.

No attempt should be made to illuminate everything in sight; the main features of interest should be selected and where visitors are likely to follow a set route a sequence of lighted scenes can be revealed as they make progress. With careful planning it is possible to present a variety of illuminated views to the observers as they walk around the main pathways. The availability of viewing directions and the practicality of concealing lighting equipment will determine the feasibility of influencing visitors to follow a pre-determined route through the garden.

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4.16.1 Pathways and

m flower beds

Figure 4.4 Mushroom luminaire.

If it is wished to vary the scene or to provide variety during the progress of the evening, a dimming or switching system can be used. Such changes can be subtle and enhance the quality of the lit effect. In selected areas tungsten or tungsten halogen sources could be used in conjunction with dimmers and a suitable form of programmable control system.

As far as practicable all floodlights should either be screened from view by mounds, shrubs, bushes, boulders or specially designed flower tubs, or be recessed into well drained pits below ground level. Lighting equipment in public parks and gardens is a favourite target for vandals and should be strongly constructed to minimise damage. It is important to ensure that any exposed cables and connections are installed to the current regulations. Where flexible cables are used water tight junction or socket boxes are recommended.

A maintained illuminance of about 10 lux should be provided on paths. For safe movement an absolute minimum of 0.2 lux with a preferred minimum of 1 lux should be provided. On steps and where there are other hazards an illuminance of up to 50 lux may be necessary. The uniformity is not important so long as there is a graduation from bright to dark, indeed the lack of it may be beneficial to the appearance. For security it is important that people can see others moving in the distance and that there is facial recognition close to. The former can be provided by placing luminaires so that people can be seen in silhouette against lit surfaces and the latter by providing an average illuminance of 5 lux distributed so that light strikes the face from the front or the side. Decorative lanterns on 4-6 m columns are commonly used for this purpose. Subject to security requirements the lighting can be made more subtle and attractive by using bollard luminaires or louvered path or step lights illuminating the required surfaces while preventing any direct view of the source.

It is often convenient to light flower beds and pathways with the same luminaires. The delicate colours of flowers and their foliage are reproduced best when lit by the white light of tungsten halogen. Small spike-mounted luminaires with 240 V PAR 38 lamps or 12 V 50 mm diameter lamps with dichroic reflectors can be mounted in beds to provide localised highlighting. The specific choice of lamp should be made bearing in mind the beam angle of the lamp in relation to its light output. Top lighting can be provided by mushroom luminaires mounted in the bed, as in Figure 4.4, or by small luminaires with special tree clamps attached to the branch of a nearby tree, as in Figure 4.5. The temporary nature of many flower beds may mean that the lighting should be flexible and easily removed.

Figure 4.5 Floodlight with special tree clamp for mounting on tree branches.

4.16.2 Trees and shrubs Trees provide many opportunities for interesting lighting effects which can be achieved at night by very simple means if the designer considers at the outset the relationship of trees to buildings.

The colour characteristics of the foliage and the effect desired should be considered carefully when deciding the type of lamp to use. If natural colours are required, an appropriate white source should be chosen. Most evergreens and some other trees respond best to light from metal halide and mercury lamps; tungsten halogen and metal halide lamps are suitable for lighting foliage that changes colour from the greens of spring and summer to the yellows, reds and browns of autumn; the warm colours of copper beech and similar trees are revealed well by the light from tungsten halogen, tungsten and possibly high pressure sodium lamps. Natural colour rendering is especially important for trees that bear blossom and fruit.

4.16.2.7 lighting effects Silhouette. Trees planted in front of a building can be brought into silhouette by simply illuminating the facade. All trees respond well to this treatment but a wide range of effects can be achieved depending on the scale and characteristics of the tree. The true beauty and unique

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4.16.2.2 Tree species

4.16.2.3 Lighting techniques

Figure 4.6 Floodlighting schemes for trec using symmetrical or asymmctrical beam floodlights located on ground close to trunk and concealed from normal angles by wattle screens.

4.1 6.3 Open landscapes

qualities of many species can best be revealed in this way, without colour, simply as an expression of pure form and pattern. Cast shadows. Light sources can be placed so as to cast multiple shadows of adjacent trees onto buildings. This ‘multiplier’ effect can be extremely interesting, for example, the size of the shadows can be exaggerated by lowering the light source so that the shadows are projected upwards. Multiple sources can increase the number of shadows and variations in the colours of these sources can create coloured shadows.

For lighting purposes it is useful to consider three basic groups of trees, identified by the following characteristics:

Open. Trees whose main character comes from the structure of their branches. These form a tracery best seen in sharp focus e.g. deciduous trees in winter, birch, ash, rowan at all seasons. See plates 10 and 12.

0 Solid. Trees with more complete canopies or crowns having dense foliage. The outer silhouette is often quite interesting e.g. most conifers, beech, chestnut, elm and most large trees in summer foliage. See Plate 11. Transparent. At certain times of the year the leaves of some species are transparent and if lit from behind can glow with colour e.g. many deciduous trees in spring especially lime and some deciduous trees in autumn, even horse chestnut which is normally very opaque.

In daylight trees are usually seen as relatively dark elements against a bright sky. Lighting can reverse this view at night by making them bright against a dark background. They can be lit by three basic methods. 0 Lighting upwards from underneath. This is achieved by mounting

luminaires at ground level and near to the tree trunk. This technique suits large, round trees with fairly open foliage, weeping willows respond particularly well to this treatment. Traditionally the luminaires have been symmetrical and asymmetrical beam floodlights sunk into the ground or camouflaged, see Figure 4.6, but increasingly direct burial luminaires are being used. They are commonly used in America and are designed to be buried flush with the ground surface and can have symmetric or asymmetric beams. Care should be taken that the beam angle is wide enough to cover the foliage without being so wide that glare is caused, louvres are often essential across the face of the luminaire so that direct glare from the source is prevented without reducing the light on the tree, Thought should be given to whether the trunk is seen in silhouette or lit.

0 Small well screened luminaires can be attached to the upper trunk or main branches, but the luminaire supports must not restrict the growth of the tree. Leather or PVC protective bands should be fitted under mounting brackets. A specialist on tree conservation should be consulted. This technique can be used to light the ground around the base of the tree as well as the foliage or by directing the light upwards it can be used to create the feeling of the tree floating. Frontal floodlighting is normally suitable for tall and narrow trees and for those with dense foliage. Symmetrical and asymmetrical beam floodlights should be mounted well away from the tree. This type of lighting is especially effective where there are only one or two principal directions of view and the tree is seen against a dark background. Depth can be created by directing the light from the side, so avoiding a flat appearance from principal points of view.

Views into a landscape from public places can be most forbidding by night. This effect can be alleviated by highlighting specific trees. These must be selected with care in relation to location and subject.

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4.76.3.7 Location

4.76.3.2 Subject

Locations must be selected for the best effect: not too distant, central to the general view and with a lighting level which does not vulgarise the natural landscape. An enhanced effect is possible where trees are situated by water.

The tree or trees selected for highlighting should be suitable subjects. It is generally unwise to select the biggest. The position of the light source is best determined by experiment on site. The object of the exercise is to achieve as much impact as possible with a limited number of sources.

4.1 6.4 Shrubs and ground In small scale areas related to pedestrian viewing, plants may be lit much as one would light objets d’art. Downlights and spotlights are extremely useful and great interest can be generated with very limited resources especially if the planting has been designed with textural, colour or formal interest. It is interesting to note that many plants are night scented and are very suited to such situations. Often smaller flower beds and plants which are intended to provide low ground cover can be effectively illuminated by decorative lighting bollards.

cover

4.1 7 Structures Area, location, or task

Maintained Notes illuminance (lux)

General areas 10 Vertical Foot-bridges 50 Working areas See CIBSE Lighting Guides: The industrial

environment and Building and civil engineering sires. Good uniformity and restriction of glare is necessary.

4.17.1 Commercial plant It should be remembered that not all the features in the landscape are individually attractive items. Civil engineering and outdoor fabrication sites, petrochemical and chemical works marshalling yards are only a few of the sites which have extensive structures. Generally they have lighting systems which provide little or no cohesive form to the installation.

and equipment

However specific or complex the location or feature it is preferable to help them visually blend in with the nightscape rather than accept them as an intrusion.

Wherever possible the lighting should make the buildings appear as an ensemble rather than as unconnected elements; careful choice of the colour of the light source can help this co-ordination. For example, tank farms with their simple cylindrical towers should be lit as a cluster. If there is a group of buildings, some of which are lit, it may be possible to complete the view by lighting a few extra components. Lattice structures such as radar stations or radio telescopes can be seen as silhouettes or contre-jour if there is one particular direction of view.

4.1 7.2 Bridges and viaducts The illuminance needed to reveal a bricige effectively will depend principally on the type of bridge, the surroundings (including the district brightness and the reflectance of the constructional material). Wherever possible the lighting should link bridges to their approaches so that they are not seen as an isolated feature in the environment. See Appendix 1.

There are too many types of bridges for the lighting to be discussed individually, they may be single span, multi-span or suspension. Materials may be steel, brick, stone or concrete.

Iron and steel bridges often have components with very little projected area. They are often of low reflectance. In this situation it is better to

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delineate the bridge by festoon lighting rather than trying to ‘wash’ the bridge with light. Under-run incandescent lamps or compact source fluorescent can be used for festoons on the cables and chains. However, access to the lamps for replacement and maintenance may prove difficult. Alternatively, the superstructure of slender bridges may be lighted by a continuous run of luminaires at parapet level, the light beam directed downwards.

Figure 4.7. Forth Bridge. High pressure sodium floodlighting at grazing angles reveals the skeletal nature of the Forth Bridge. The regular spacing of the floodlights has the effect of large scale festoon lighting accentuating the arches.

Supporting towers can usually be floodlit to great advantage using projector type luminaires with limited beam spread, mounted on s6ructural members of the bridge at the base of the tower and aimed upwards. Any piers above the tower should also be lighted to avoid the bridge having a disembodied appearance. See Plates 13 and 14.

Structures or towers which have open framework or open lattice-work may be viewed from all directions.

A survey of the structure should be made to determine the optimum luminaire positions required to obtain a visual effect that will reveal the form and enhance the skeletal quality of the framework. In principle, the luminaires should be aimed upwards along the outer side of the lattice-work to permit the flow of light to reach as much of the various surfaces at grazing angles. As both adjacent and distant observers will be glancing upwards to the structure, and as all incident light will be in the same basic direction every metal surface of the framework will appear to be lit. The effect is more pronounced if the structure is of a light colour.

Masonry, concrete and brick bridges respond more to floodlighting. The sides of these bridges, if they span a valley or cutting, can often be conveniently lit by asymmetric floodlights mounted on one or both banks. These may need to be supplemented by projector floodlights for long spans.

Floodlights should be mounted below the platform level of the bridge to minimise glare to traffic and pedestrians. The use of visors to control or re- direct spill light should be considered.

Floodlighting the under-sides of the arches can be effective either with or without lighting the sides. On river bridges this may be the only option because of access to the floodlights.

When the type of lighting system and the locations for the floodlights have been decided, their type number and wattage can be estimated by usingone of the methods of calculation described in Appendix 1. After the lighting system has been installed, the effects should be assessed critically, and adjustments made on site.

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4.1 7.3 Foot-bridges

4.1 8 Statues and scu I p tu res

Wherever possible provision should be made for incorporating the floodlighting equipment in the structure. If lighting has to be placed at considerable distances away it is difficult to minimise glare to traffic and pedestrians passing beneath. Any lighting must not distract the attention of road, rail or marine traffic passing below or over the bridge or viaduct and if any coloured light sources are used, special care must be taken to prevent confusion with railway signalling or navigation lights. Particular care should be taken regarding glare from high intensity floodlights. Louvres or shields will almost certainly be required. For rail bridges it is necessary to satisfy the rail authority and for roads BS 5489'4' should be adhered to.

Usually a foot-bridge is illuminated in the same manner as the approach paths which provide access to the bridge, and this may be with the use of columns or bollards. If the bridge has some form of handrail or balustrade luminaires may be concealed in these features. The constant risk of vandalism should be taken into account when selecting luminaires at this level.

I t is necessary to avoid glare to both pedestrians and drivers especially if it is intended to indicate the route with floodlighting. Floodlighting luminaires should be equipped with suitable louvres to provide glare control when needed.

If the bridge is going to be considered as a landscape feature you should refer to Section 4.17.2.

The primary aim for the designer concerned with the floodlighting of these features must be the achievement of a natural appearance. This aspect cannot be over-emphasised where the human form is involved for the relationship of shadows and brightness, if not fully considered, can produce a visual effect which may be quite grotesque.

Many of the techniques used in building floodlighting can be used with individual features but specific requirements need to be borne in mind.

A statue or sculpture may be traditional or abstract and be intended for viewing either from within a restricted angle or from all sides. Modelling is always important and lighting is required that reveals the form and details of the sculpture and gives it prominence within the surroundings. Lighting at night gives an exciting opportunity to create an alternative perception to that of daylight. The particular work should be studied with a view to expressing features that are not so obvious under daylight. Works in light coloured materials are normally revealed best when brighter than the background, but dark statues (e.g. those in bronze) are often presented most effectively in silhouette.

Mainly because there is no diffuse light from the sky it is often difficult to achieve coherent modelling outdoors at night of sculptures that need to be seen from all sides. Light projected principally from one direction may produce a pleasing effect when the sculpture is viewed from a particular angle but when the viewing position is changed the shadows may confuse or distort the appearance. On the other hand if there is a significant flow of light from two or more directions multiple shadows will be formed which may also be confusing. Each sculpture is different and experiments must be made on site to determine the best lighting system.

Bas-relief sculptures are usually seen to advantage when light is directed along, and almost parallel to, the face of the sculpture thus producing strong shadows that emphasise the relief. PAR lamps, low voltage dichroic lamps or tubular lamps can be used.

\

Figure 4.8 Floodlighting scheme for srarue using a symmetrical beam floodlight mounted on roof of adiacent building: light directed about 70° in azimuth KO front of statue: floodlight incorporates matt black screen.

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There are three basic methods that can be used for lighting statues and sculptures: spotlighting from above; spotlighting from below; close offset highlighting.

4.1 8.1 Spotlighting from above

Traditional statues and other sculptures intended for viewing primarily from in front can be floodlit from within the forward hemisphere using symmetrical beam floodlights located some distance away and at a height rather greater than that of the statue, see Plate 15. The ideal angle used in theatre lighting is 45’ to the side and 45’ up from the horizontal. A natural modelling effect will be created if this key light is balanced with fill light, of about one tenth the intensity of the main beam, directed from 45’ to the other side to soften the shadows. It can be very effective to provide a high back light at a similar intensity as the key light. This method should be used with care so that ‘overshoot’ glare is avoided. If the statue is to be observed at close quarters then the spill light must be such that it does not shine into people’s eyes. The shape of light beams can be matched closely to the outline of the statue and irregular patterns of light can be projected by profile spotlights. The light can be kept off the background so the statue will stand out in dramatic isolation. These effects are achieved by standard, or specially cut, ‘gobo’ masks. Irregular dot or ‘breakup’ patterns are used to simulate the effect of sunlight through trees.

4.1 8.2 Spotlighting from below

A useful alternative is to use buried luminaires set into the ground. These should be positioned that the light hits the statue or sculpture at an incident angle of45’ to 60’. When using this method it should be borne in mind that the effect will be the opposite to the natural lighting effect, the light will be coming from underneath. This can create some stunning effects but care should be taken that the effect is not grotesque. These luminaires can either incorporate directional low voltage lamps or an asymmetric reflector. Consideration should be given to the use of matt black louvres across the lens to avoid glare in the observer’s eyes.

4.18.3 Close offset highlighting

It may be appropriate to mount small discreet luminaires on the plinth or elsewhere on the structure. The intensity of these luminaires should be carefully balanced with that of any others aimed at the object and they should be used to highlight particular features of the statue. This can particularly enliven the appearance of a dark statue seen in silhouette.

4.1 9 Monuments and Area, Maintained Notes location, or task

memorials

Ancient monuments, castle ruins, memorials, features requiring colour Access walkways, entrances 50 Adjacent car parking areas 10

See Section 5.3

The task of floodlighting monuments requires careful evaluation. The project may be a national historical monument requiring a high degree of expertise in lighting design and application to achieve a desired visual effect, or it may be a fairly simple obelisk, best suited to a more traditional lighting approach as detailed in the section on statues and sculptures.

Ancient and historic monuments should be floodlighted in a manner that indicates their specific character, age and if it can be expressed practically, the historic significance.

The size of the monument along with its setting will often dictate an approach involving lighting from the ground or highlighting from

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4.20 Clocks and sundials

concealed luminaires mounted on the structure. A combination of the two approaches can have a stunning effect. Concealed highlighting should be used to pick out arches, reveals, statues and other architectural features, while the lighting from the ground should be of a lower intensity and used as a fill light to unite the highlight areas. Careful consideration should be given to the background in deciding on illuminance levels; often only a small amount of light is needed to create an effect.

Floodlighting schemes for ancient monuments are similar, in general, to those for historic buildings. Account should be taken of the effects of erosion, and if roofs and walls have been destroyed, or partly destroyed, the lighting should be designed to achieve an effect without an apparent cause.

Floodlighting schemes for castle ruins and similar monuments should be designed to emphasise the massive character of the structures and to reveal the form of towers and other prominent features.

The historic significance of a monument can sometimes be suggested by coloured light; for example, blue light may be used to create an air of mystery, and red light to indicate a battle site.

Attractive effects are sometimes achieved by using light of different colour at different times of the year. For example, metal halide lamps are used in winter to illuminate the building, their bluish-white light suggesting the cold season; in summer, high pressure sodium lamps are used to give an appropriate impression of warmth.

The splendour and magnificence of an ancient monument can be revealed to the full only by close and continuous co-operation between the project architect, the lighting engineer and, where appropriate, the archaeologist, whose chief concern is the preservation of the monument. Lighting equipment should not be attached to the fabric of the building unless special permission has been given, and cable routes must avoid archaeological remains or the burial grounds of ecclesiastical ruins; foundations must not be disturbed.

Area, location, or task


Dark surroundings, light 200 surface Bright surroundings, light 500 surface Sundial (large) 100

(small) 200 Clock towers See Section 5.3.

This Section discusses the lighting of large historic and modern clocks incorporated in clock towers or building facades. The lighting should enable the time to be read easily from a distance at night, reveal clearly the rich decoration that is a characteristic of many historic clocks and, where appropriate, provide a point of visual interest on a building facade.

Clock faces of light colour can be floodlit to provide a bright background against which the hands and numerals are seen in silhouette. If the facade of the tower on which the clock is mounted is floodlit to display its architecture, additional light should be provided on the face to give it prominence, as illustrated in Figure 4.9. A symmetrical beam floodlight may be located at a distance and trained on the face or, if the structure permits, an asymmetric or double asymmetric beam floodlight can be mounted on the tower or facade. Floodlights for both systems should have a

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/ Floodlight with 1 OOW PAR38

Figure 4.9 close offset floodl,ghtlng of clock face and tower.

I Floodlight with ' 50w PAR38

floodlomp spot lamp


4.21 Flags

beam spread which ensures that as little light as possible faIls outside the face. Whichever system is used it may be difficult to prevent confusing shadows being cast by the hands and numerals and experiments on site will usually be necessary to determine the best arrangement.

The lighting problems may be simpler if the clock has a translucent face which can be lit from behind. Tubular fluorescent lamps, or other lamps with a long rated life, are mounted at the back of the face and positioned to provide reasonably uniform luminance over its surface. Ingenuity may be needed to prevent shadows being cast on the rear of the face by the clock mechanism.

The lighting of longitudinal sundials may be regarded as decorative objects on a facade. The characteristics of the object should be brought out. It is desirable to light it in such a way that a distinct shadow of the gnomon is cast across the face.

Arca, locarion, or task


Dark background light flag 200 Bright background light flag 500

Towers See Section 5.3.

The designer of the floodlighting installation may have to include for the illumination of any flags or pennants that are displayed and particularly if flown from towers, pinnacles or roofs.

PAR lamps in luminaires mounted below and on each side of flag

PAR38 lamps concealed within vertical metal tubes

(4 (b) (4 Figure 4.10 Floodlighting schemes for flags (a) mounted on roof of building (plan view); floodlights aimed centrally and upwards to cover full height and width of flag (b) on pole at angle to building face (c) on cluster of poles in precinct or similar area

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Flags should be brightly lit to stand out prominently against their background and their colours be revealed as vividly and naturally as possible. Flag poles or other forms of support should be clearly visible in order that the flags do not appear to be floating as bits of material unsupported in space. The luminaires should be spaced in such a way that the complete flag will be illuminated irrespective of the angle at which the flag is blowing in the wind.

I t is essential to use lamps that have good colour rendering properties. Tungsten halogen, tungsten filament, and metal halide lamps are generally suitable.

A flag on the top of a building should be illuminated by floodlights arranged all around it and mounted on the roof as shown in Figure 4.10 (a), or at some other location below the flag. Flags on poles set at an angle to a building face .may be lit using compact luminaires - Figure 4.10 (b) - those using low voltage tungsten halogen being particularly suitable. Flags flown from poles set in the ground are usually illuminated by floodlights mounted on the ground or recessed into it, direct burial luminaires being particularly suitable. Where there are group of flags in a precinct or similar area it may be convenient to use a system of tubes or other structure to conceal the lamps. Figure 4.10 (c) shows the lamps concealed within vertical metal tubes.

4.22 Fountains and Water is a very attractive element of the landscape and can be used to create a sense of tranquillity or gaiety. Still water is a perfect medium for the reflection of floodlit buildings, sculpture and trees; fountains and cascades sparkle and glitter when suitably lit whilst distorted reflections of light from moving water can create interest on walls and other surfaces.

pools

Vertical jets are often lit by symmetrical beam submersible floodlights, see Figure 4.1 1, so positioned that the light is projected through, or along, the water streams. The beam angle of the luminaire is critical and should be calculated in relation to the height of the jet in relation to its width, A hemispherical bell jet would be lit by a wide angle luminaire while a tall 25 m jet would use a narrow angle beam with a high peak intensity. Low voltage equipment is extremely useful for this not only for electrical safety reasons but also because of the choice of beam angles and intensities. There is a choice of low voltage sealed beam lamps from 12 V 25 W and 50 W PAR 36, with beam angles from 5' to 98' with various peak intensities. See Plate 16.

Symmetrical beam floodlights are also used for lighting water sprays and, depending on the distance of the water projection, may be required at both the beginning and the end of the trajectory; Figure 4.12 shows typical floodlight positions for inclined and oblique jets, A combination of automatic dimming and cyclic changes of colour and jet patterns can enhance the spectacle although care should be taken not to go too far and spoil the overall effect. Ornamental fountain basins and rocks used to produce turbulent and diffusing water cascades should be backlit by concealed light sources, see Figure 4.12 (d). Lighting up cascades from the bottom with narrow angle lamps can produce a dramatic effect particularly if the light can project through the water onto a wall or other surface

6 \i\\ A# # &

,/--:. , //$p&+ creating a ripple effect of moving water.

.>.. .. . The beauty of a floodlit tree-filled island viewed from the banks of the mainland is greatly enhanced by reflections in the water. Submersible tungsten halogen lamp floodlights positioned near to its banks and mounted below the surface of the water may be used, or rainproof floodlights may be mounted just above water level. The second method has the advantage that

Figure 4.11 Vertical jet illuminated by narrow spread symmetncd beam submersible floodlights.

33


light losses caused by absorption and scattering of the light are minimised. To obtain a balanced picture of patterned foliage each floodlight should have side wings or lateral louvres which can be adjusted individually. Taller trees in the centre of the island will need additional light and symmetrical beam floodlights may be mounted on the far banks to provide this,

Swimming and ornamental pools will benefit from underwater lighting. They are generally lit below the surface from the side walls with specialist luminaires having narrow angle or fan shaped beams.

The luminaires may be located to suit two types of lighting system. They may be placed into a wet niche which would be a form of simple recess in the wall side of the pool or fountain and this would utilise appropriate submersible floodlights. Alternatively, a niche may be dry such as a sealed receptacle into which the luminaire may be placed, or a translucent lining in the wall behind which the luminaire would be placed and maintained.

Fibre optics may also be used as a media to transfer light from a central core to numerous light terminals around the pool or spa. Electrical safety and ease of maintenance would be particular benefits of a system of this type.

High ambient illumination tends to negate the relatively low brightness produced by underwater coloured light. Coloured light may have a tendency to reduce the effect of contrast with the adjacent surroundings or may have the effect of increasing the adaptation level of the viewer. It is, therefore, desirable only to consider coloured light if the following parameters can be met:

not less than 500 lamp lumens per square metre of water area; 0 and luminaires positioned no more than a maximum depth below the

surface of 0.4 m.

.-,

1 OOW PAR flood

at base &waterfall

Figure 4.12 Lighting arrangements Tor ornamental water features. a) vertical jet: narrow spread symmetrical beam floodlight b) inclined jet: symmctrical beam floodlights at beginning and end of trajectory c) oblique jers: symmetrical beam floodlights at beginning and end of trajectorics d) cascade.

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4.23 Festive illuminations

Extreme care must be taken to ensure that the luminaires used in all water features must be securely fixed and electrically safe, with full account taken of the effects of any undue water turbulence and the risk of any interference by unauthorised persons. Some form of physical barrier should be installed to prevent unauthorised access to underwater luminaires on boating lakes and pools open to use by the public. All equipment should be inspected frequently, particularly for security of fixing, ,corrosion and chafing of supply cables. The use of residual current circuit breakers should be considered for all supplies to underwater lighting systems.


Pathways Water (still)

Water (running)

Festoons

Steps, stairways and hazards 50

Keep columns or supports low or use bollards. Position lamps to produce good reflectancc in water. Position lamps behind or below and aim to strike water at obliquc anglcs. Do not use indiscriminately. Can be used on bridges to outline shape or suspension. All adjacent surfaces to be light.

Festive lighting is often used at special events and for traditional celebrations such as Fete Days, Christmas and New Year.

When any organisation decides to install a system of festive decorative lighting and particularly if this involves any form of street illuminations a number of steps have to be taken. Permission may have to be obtained from the local authority if any form of festive lighting is to be displayed in the streets or if other street furniture, equipment or signs are involved.

It may also be necessary to liaise with a regional electricity company who will be able to assist with advice regarding the availability of a temporary supply of electricity and the relevant tariff. The body responsible for organising the festive illuminations may not have the services of an electrical engineer available. In such cases it is advisable to secure the services of a qualified engineer who may best liaise with the authorities concerned and also advise in the design, erection, operation and final dismantling of the display.

The installation of cabling and the fixing of equipment in busy streets and precincts can present special difficulties. It may be necessary to install and erect equipment late at night. This calls for careful planning and security and a need to ensure that all materials are to hand since delays in installation may be costly.

Effective operation is important for economy in the use of energy. Late afternoodearly evening is likely to be the important period of operation for commercially orientated festive displays, mid to late evening operation for the non-commercial users. In both cases, however, there may be natural or man-made assets within the area which may be exploited for inclusion to provide effective focal points in a lighting display. In this respect, fountains, sundials, clock faces, stretches of canals or rivers and their bridges can all be useful assets to the illuminated landscape.

Public safety is a prime consideration. All electrical work should comply with the IEE regulations applicable to temporary installations and the use of good quality lighting equipment should be a prudent choice to promote safety and reduce the likelihood of breakdowns in the system. Operational conditions can be demanding and installations should be designed to withstand severe weather, vandalism and inadvertent damage. Where

35


catenary suspensions are used, the mechanical strength of the cables and the fixing which serve to support the cable must be sufficient to withstand the strains imposed by the weight of the equipment and the additional drag caused by high winds and snow or ice. For this reason moulded lamp holders which are bonded permanently to their supply cable and are thus rainproof are recommended for use as festoon strip. Lamp holders which offer pin type contacts intended to collect a supply by piercing the cable insulation should not be used to achieve festoons of lights. Good electrical contact is unreliable and the risk of an electrical shock to anyone handling the cable is considerable.

Cables suspended as a catenary system should be supported at a height not less than 3 m above ground level, and if decorative lanterns are mounted on 4-6 m columns as additional points of interest it is important that neither the festoon lighting nor the supplementary luminaires become sources of glare.

One of the most exciting additions to any outdoor festive lighting display is the use of laser technology, which can produce quite spectacular lighting effects. However, there are special considerations needed with the broad operational use of lasers and care must be used in their application. Compliance with local authority requirements may be necessary and it is advisable to seek the guidance and assistance of the local environmental health officers before the inclusion of laser techniques. It is also considered prudent for the laser projector equipment to be operated under the supervision of the equipment specialists.

4.24 Outdoor Area, Maintained Notes bandstands and locationJ illuminance

or task (lux)

Audience areas 20 1 lux during performance. Access points, exits, main 50 pathways

Bandstands general 300 Music stands 300 Inclincd plane.

auditoria

Car parking 10

Open-air bandstands range from the traditional Victorian structures, which are still to be seen in many of our parks and on seaside promenades, to the often huge and spectacular outdoor orchestral stages such as the famous Hollywood Bowl, which can accommodate an audience of over 20,000 in the open-air.

Although mass enjoyment of music in the open-air night-time environment may not be a new phenomenon, the recent increase in the innovative style of touring concerts and pop and rock shows have introduced a new and vibrant dimension to live outdoor entertainment. Modern rock concerts are generally held in vast open-air arenas and are specialised and highly sophisticated events which bombard their audiences with an experience in sound .and lighting effects.

Such concerts are generally stage-managed by organisations that specialise in producing this kind of show. All the sound and stage lighting equipment is brought into the venue especially for the event and set up on a variety of towers, trusses and booms. The very detailed planning and specialised programming required for a presentation of this kind is not dealt with in this Guide.

The maintained illuminance throughout the auditorium or auditorium area should not be less than 20 lux and with a uniformity ratio of not less than 0.1

36


except during the performance itself when only safety lighting generally needs to be provided.

Security and safety are of prime importance in public spaces of this kind. As there is generally a lack of choice in audience viewing direction, the lighting designer must evaluate possible solutions for the acceptable positioning of the columns and supports and verify the quality of the proposed design. Any areas of shadow or inadequate illumination which may possibly be unsafe must be avoided. A successful system which provides good uniformity and a desirable quantity of semi-cylindrical illuminance which permits good facial recognition may be readily achieved by using a luminaire that distributes its light output outwards rather than downwards. Decorative lanterns supported on 5-8 m poles or columns may be found appropriate.

It could also be advantageous to design the system for dimmer control as this would permit the illuminance to be reduced during the concert - but the lowest value must never be less than that stipulated by the responsible authority for safety. In some instances the need to ensure maintenance of public order may prohibit any reduction of illuminances. Emergenc lighting will be required and should follow the principles of BS 5266" . Further guidance on emergency lighting can be found in Section 5.4 of this document.

P

Smaller modern bandstands are often covered and may afford the designer an internal suspended acoustic ceiling into which luminaires for lighting the area beneath can be recessed. If downlights are used, forms of supplementary lighting must be installed to alleviate the predominantly downward direction of light and thus improve the modelling of the performers' faces. Care must be taken that the positioning of such supplementary sources does not produce undesirable glare to either musicians or audience.

Music stands may need to be individually provided with illumination, and an illuminance of 300 lux should be provided on the inclined music. This may be typically achieved by a 30 W tubular double-ended lamp in a suitable housing, providing general illumination is also available.

Open-sided bandstands of the more traditional design are not usually provided with any interior suspended ceiling. Luminaires are therefore usually affixed to the underside of the roof structure panels, any electric wiring being suitably protected from the ingress of rain. General illumination should be supplemented by light on each music stand and the lamp housing must be weather-proof and fully protected against electric shock.

Low wattage clear and coloured incandescent lamps in weather-proofed holders may be spaced around the outside edge of the stand roof to provide an appropriate touch of gaiety. Alternatively, a festoon of disco type light tubing with an animated effect may be preferred.

For the overall safety and security of the audience, any seated areas should not have to rely upon any fortuitous spill light from the bandstand. Adequate levels of lighting should be provided throughout the public footpaths which give access to the seating and the adjacent environment to the bandstand.

4.25 Son et lumi&re The technique of using light and sound to create and enhance special effects was first applied as long ago as 1952 in France at the stately old chateau of Chambord. Since that time son et lumigre spectacles have thrilled and

37


delighted citizens and tourists the world over and have become an important source of revenue for their sponsors.

Son et lumiere productions are nearly always associated with historic buildings or events. Typical of recent presentations being the Egyptian Pyramids at Gizeh, the Roman Forum, the Regent’s Palace at Brighton and Greenwich Palace.

The objective is to utilise sound and light sequences to re-create an historical story through the stimulated imagination of the audience.

Son et lumi6re performances can be presented as a stage setting with the audience viewing from mainly one direction as in the theatre, or they may be staged within cathedrals, palaces or archaeological ruins where the audience is not restricted to one permanent place or direction of view.

Techniques of synchronisation and control have reached a refined and advanced level and son et lumiere is now a contemporary art form that uses state of the art technology in electro-acoustics. The equipment range is fully automatic. The central control unit is designed to handle the synchro signals from multi-track tapes, some of which carry music, sound effects, voices, all of which could be mono, stereo and travelling sound. Other tracks provide command signals for the accurate control and co-ordination of the various light and sound circuits.

Generally light sources producing white light are utilisqd in luminaires equipped with adjustable shutters and louvres which also support colour filters or coloured front glasses to produce complex coloured lighting effects. Typical of these effects are the combinations of red/yellow to reproduce sunlight, and bluelgreen for clear moonlight.

Typical types of lighting are contained in the following list. General or basic floodlighting. Dynamic, effect or ambience lighting, which would be variable in direction, intensity and colour.

0 Highlighting of the architecture, Accent lighting of the smaller features or details, often using specially designed projectors.

0 Glancing or grazing light. 0 Back, or contre-jour lighting.

Luminaires are often recessed into trenches which run parallel to the facades. In the daytime trenches can be closed and secured by hinged metal covers which totally conceal and protect the equipment from damage and the weather.

Son et lumiere are very individual productions. When such a presentation is contemplated specialists should be consulted.

4.26 Illuminated Signs Area, Maintained Notes location, illuminance or task (lux)

and hoardings

Externally illuminatcd signs Low district brightness 100 On sign.

On sign. High district brightness 500

A sign communicates traffic information, advertises products and services, promotes brand names and identifies shops and stores. Illuminated signs

38


can be conveniently divided into two main categories; those related to movement and direction, and those utilised commercially for advertising and image promotion. None can be wholly disassociated from the landscape or from the buildings and spaces in-between.

With the use of new materials, new light sources and advanced techniques an ever increasing variety of signs can quickly gain the observer’s attention through the combined use of size, colour, and movement.

It is often required to describe or identify a certain type of illuminated sign and this task is most easily done if all electrically lighted signs are considered in terms of the method by which they are illuminated.

4.26.1 Luminous This category probably represents the greatest proportion of all illuminated signs, and generally comprises a translucent plastic or diffused glass fascia panel upon which translucent letters or designs may appear in contrasting colours, or opaque characters will appear in silhouette.

background signs

Signs of this type are achieved by backlighting an acrylic or glass panel which may be either internally pigmented, externally painted or preferentially opaque to permit selected areas of light to show. In the case of large areas of luminous panel, uniform brightness is an important factor. The quality of this effect over the desired portion of the sign face is directly proportional to the following:

quality of pigmentation or paint film; 0 the inter-reflectance characteristics of the sign enclosure;

and the provision of the optimum clearance between the light sources, usually fluorescent lamps, and the sign face material.

The correct clearance will prevent ‘hot spots’ of source brightness appearing on the face of the sign.

Quality of both design and manufacture of an illuminated sign is important to ensure the best attraction value in both day and night environments, and the golden rule of visual effectiveness is simplicity.

Good contrast should be provided between the ‘message’ and its background. If the background brightness is too bright then you will never be able to read the sign. This may be achieved by differences in colour, or differences in brightness. Often the use of variations in colour will also achieve differences in perceived brightness. Many signs are required to have very light letters on a dark background.

4.26.2 Exposed tubular Illuminated letters and designs are seen against a non-illuminated background. Neon or cold cathode glass tubing may be arranged as exposed lamps, or designed to follow the contours of raised letters and designs.

lamp signs

Cold cathode or neon are usually associated with signs of this type. The letters or designs are constructed of gas-filled tubing which when subjected to high voltages becomes luminescent in the colour characteristics of the gas filling used, or of the fluorescent phosphors coating the inner wall. This form of signage is usually specially made to provide the user with a distinctive recognisable identification. Often lamp tubing can be concealed behind opaque letters of the same shape, the resultant visual effect being to silhouette the lettered facade sign.

4.26.3 Signs externally floodlit

This form of illumination is often appropriate for many large advertising hoardings. Acceptable uniformity over the entire sign area together with a strict avoidance of reflected glare are the main objectives.

39


This form of sign lighting is appropriate for the smallest wall-mounted public house sign or the massive city centre advertising hoarding. At each end of the scale the achievement of a good quality illuminated advertisement involves the careful selection of facing materials and suitable luminaires with light sources at precise spacing. Uniformity of illumination over the area of the sign and its brightness are the important factors to consider, and thus it is necessary to address the problems of which light sources to use, how many are needed and what spacing is best to obtain a reasonably uniform luminance.

Figure 4.13. Indescon Court sign. A tubular housing for a fluorescent lamp controls the spread of light and provides effective lighting for the vertical sign.

Many signs, particularly roadway, are designed primarily for daytime viewing conditions. In order to provide continuity of communication, night-time illumination must not alter or diminish the colour message as perceived by the motorist. Therefore, the colour rendering properties of the light source used is important for all types of colour sign.

There are some general guidelines for the luminaire geometry of vertical signs, hoardings and poster panels, see Figure 4.14:

S > 2.50

0 < 0.25h where:

S = distance between luminaires 0 = distance from sign to axis of luminaires h = height of sign Figure 4.14 Typical lighting on advertising

hoarding. Choice of the illuminance required depends on the district brightness. The views and opinions of the local Planning Authority should be sought. The sign brightness should not be overdone but should be sufficient to make it stand out in contrast against the surroundings.

The lighting must be restricted to the area of the sign and should not be permitted to produce direct or reflected glare. The use of floodlights with a wide light distribution will often provide good uniformity but wastes spill light that flows away beyond the area of the sign. This spill light can often produce undesirable luminances on adjacent surfaces and possibly glare to the nearby residents. Usually, even the smallest of signs or posters can only be successfully illuminated by using more than one light source. All the

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5

possibilities should be considered. Various aiming angles at different spacing; different offset distances, and various lamps. The use of computer program or graphical techniques can save time spent on many hours of trial and error.

Uniform luminance is a desirable objective and will considerably enhance the overall effectiveness. Uniformity of sign illuminance is expressed as a ratio of maximum to minimum levels on the sign face. A maximum/ minimum ratio of 4: 1 is considered desirable.

The location of lighting equipment should not obstruct the legibility of the sign from normal viewing positions, or produce any shadows during the day-time that may interfere with the legibility of the sign.

Where floodlights are located on the ground or sited remotely from the sign it is advisable to ascertain whether the location chosen is prone to vandalism. Most authorities recommend locating the luminaires at the bottom of the sign.

The luminaire and lamp should require a minimum of maintenance attention and be energy efficient to provide low operating costs.

The colour rendering of the light source is important for all types of sign. Efficacy and lamp life are also desirable and the sources that meet all these requirements are fluorescent, mercury de-luxe and metal halide (clear and phosphor coated).

Incandescent, tungsten halogen and high pressure sodium whilst possessing individual aspects that may be acceptable under certain conditions, must be considered as less desirable.

Lighting techniques

Area lighting For lighting of external working areas the CZBSE Lighting Guide: The industrial should be consulted. If such lighting is well planned and installed it will repay the cost of its investment many times in safer and more efficient work operations. It will also make possible the greater use of plant and equipment and serve to protect the facilities from vandalism and theft.

5.1

There are two basic forms of area lighting: conventional low mounted system; and high mast or high mounted system.

5.1.1 low mounted systems

5.1.2 High mounted systems

Where small to medium sized areas are concerned it is likely that wide beam light distribution type floodlights or even roadway lighting lanterns can achieve satisfactory lighting conditions. Low mounted systems would generally utilise luminaires mounted at heights above the ground of 8-12 m.

Such a system is limited to areas that are capable of being uniformly illuminated from the perimeter, or areas where it is practical to have relatively closely spaced columns across the whole area. When these lower mounting heights are employed it is normally accepted that the spacing to mounting height ratio of 3:l should not be exceeded unless special maintenance difficulties or local planning requirements influenced greater distances between columns.

Large areas of open space may beneficially be lit to good lighting effect by using high mast floodlighting techniques. High mast installations would normally be employed at heights between 15 m and 30 m.

41


5

possibilities should be considered. Various aiming angles at different spacing; different offset distances, and various lamps. The use of computer program or graphical techniques can save time spent on many hours of trial and error.

Uniform luminance is a desirable objective and will considerably enhance the overall effectiveness. Uniformity of sign illuminance is expressed as a ratio of maximum to minimum levels on the sign face. A maximum/ minimum ratio of 4: 1 is considered desirable.

The location of lighting equipment should not obstruct the legibility of the sign from normal viewing positions, or produce any shadows during the day-time that may interfere with the legibility of the sign.

Where floodlights are located on the ground or sited remotely from the sign it is advisable to ascertain whether the location chosen is prone to vandalism. Most authorities recommend locating the luminaires at the bottom of the sign.

The luminaire and lamp should require a minimum of maintenance attention and be energy efficient to provide low operating costs.

The colour rendering of the light source is important for all types of sign. Efficacy and lamp life are also desirable and the sources that meet all these requirements are fluorescent, mercury de-luxe and metal halide (clear and phosphor coated).

Incandescent, tungsten halogen and high pressure sodium whilst possessing individual aspects that may be acceptable under certain conditions, must be considered as less desirable.

Lighting techniques

Area lighting For lighting of external working areas the CZBSE Lighting Guide: The industrial should be consulted. If such lighting is well planned and installed it will repay the cost of its investment many times in safer and more efficient work operations. It will also make possible the greater use of plant and equipment and serve to protect the facilities from vandalism and theft.

5.1

There are two basic forms of area lighting: conventional low mounted system; and high mast or high mounted system.

5.1.1 low mounted systems

5.1.2 High mounted systems

Where small to medium sized areas are concerned it is likely that wide beam light distribution type floodlights or even roadway lighting lanterns can achieve satisfactory lighting conditions. Low mounted systems would generally utilise luminaires mounted at heights above the ground of 8-12 m.

Such a system is limited to areas that are capable of being uniformly illuminated from the perimeter, or areas where it is practical to have relatively closely spaced columns across the whole area. When these lower mounting heights are employed it is normally accepted that the spacing to mounting height ratio of 3:l should not be exceeded unless special maintenance difficulties or local planning requirements influenced greater distances between columns.

Large areas of open space may beneficially be lit to good lighting effect by using high mast floodlighting techniques. High mast installations would normally be employed at heights between 15 m and 30 m.

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5.2 lighting for amenity

High-mast floodlighting generally uses a smaller number of floodlights of a higher wattage when compared to those required in a conventional area lighting system. The light sources used would be mounted higher and further away than would be necessary with an installation at lower mounting height. A high mast system would normally provide for area lighting by supporting the floodlights at 15-30 m. For lighting very large areas masts are available in the range 30-60 m.

Floodlights used on high towers, commonly with symmetrical reflectors, generally need to be individually aimed to achieve a satisfactory uniformity of lighting from the system, and where such floods are aimed in all directions from the head-frame it is possible to use a 7:l spacing to mounting height ratio, provided that all parts of the area being illuminated receive light from at least two of the towers.

High mast and high tower systems are suited to areas where the prime requirement is to save space in preference to restricting expenditure; for example at container terminals, and even for large construction site lighting where the masts may be moved and re-used. Many large open areas such as steel works, engineering and fabrication works, chemical works and construction sites often require less critical aiming patterns than is necessary when using narrow beam floodlights. For this type of area, floodlights that provide a fan shaped light distribution are acceptable. In these instances it may be expedient to combine a high mast system, which uses wide beam floodlights at 30-45 m to provide general area lighting for the central part of the area, with a conventional area lighting installation to illuminate the perimeter zones and access roadways.

Attractiveness, delightfulness and pleasantness are all ways of expressing amenity and these expressions lend themselves ideally to the purpose and objective of amenity lighting. However, such objectives are not easy to use as a basis from which a lighting decision can be made.

The application of amenity can be both general and specific and must be made on the basis of requirements and economic considerations. There are few, if any, index listings for either criteria or design criteria and often when amenity lighting is referred to it deals with the problem in a circuitous fashion.

Sometimes the term ‘amenity lighting’ is characteristic of lighting conditions that are provided as some compensation for a situation where there may be a total deprivation of seeing ability. Generally, however, references to amenity lighting infer that such lighting should assist the safe movement of persons and vehicles in an exterior area at night-time and that it may aid the performance of outdoor work and may have some prestige or publicity value. The distinction between amenity and prestige is blurred and as this Guide will show there exists a sizeable range of considerations, beyond the functional effect on night-time vision that should influence the choice of illuminance.

Very often, as well as creating safer conditions, the impression produced by exterior lighting can be amenable as well as more prestigious, in spaces such as parks, gardens, pedestrian areas and walks, terraces, balconies and courtyards.

A fairly high diversity of illuminance is acceptable for most amenity lighting but it is important that the equipment and its placing should relate to the human form and not dominate. Sources placed below eye level and projecting downwards, generally, achieve a most pleasing effect. Although they do not represent a very efficient way of lighting an external area due to the increased cabling and maintenance costs involved; such investment

42


should be weighed against the benefit accrued from the quality of the visual environment produced.

5. Floodlighting of Many of Britain’s towns and cities owe much of their individual character to fine historic buildings which can boast rich, ornate facades and beautiful architecture.

Other places, perhaps less fortunate in having a legacy of fine historic buildings, nevertheless are sure to have a liberal provision of interesring buildings of one form or another, churches, monuments and other features, together with an increasing wealth of modern architecture , albeit that their impressive facades may conceal commercial office complexes, precincts, flats and hotels.

b u i I d i ng s, structures and features

The grandeur of the historic and the qualities of the modern can both be accentuated during the hours of darkness by well conceived installations of floodIighting. In the case of office buildings which are likely to contain offices and retail stores, floodlighting will attract attention, create a favourable impression, and thus becomes a subtle and dignified, yet extremely effective form of advertising.

Although the primary objective of lighting a building facade or its surroundings may not have been to prevent illegal entry or theft, it has to be acknowledged that floodlighting is an effective security measure. Facade lighting in particular enables observers on the street to easily perceive movement and people revealed in silhouette against the brightness of the building surface.

Daylighting is general and non-selective; artificial lighting can reveal specific buildings, stress particular characteristics and its effects can be modified. Thus the designer is able to select exactly what needs to be accented or ignored. Most buildings of any merit can be successfully floodlit and the techniques for achieving a good effect cannot be based solely on the exact science of illuminating engineering but must include an appreciation of the aesthetic values of the architecture. This is particularly applicable in the floodlighting of cathedrals, castles, churches, civic buildings, bridges and ancient monuments which respond remarkably well; not only are these buildings themselves enhanced but the landscape as a whole. See Plate 17.

Any floodlighting project cannot be commenced until a comprehensive survey has been made of the building and the surroundings in which it stands. It is essential to study the features of the facade under the conditions of natural light and preferably to view it in sunlight at regular times throughout the day. A detailed appraisal.of the effects created by variations in the angles of sunlight striking the architecture can reveal which features of the building are the most attractive and need to be enhanced with artificial lighting.

Many early architectural styles were onIy considered in relation to the natural light of day and decorative illumination after the sun had set would have been unthinkable. There is now no limit to the forms a modern building may take and architects are more inclined to the precept that the building should also be attractive to view after dark when the various surfaces and textures may be iIluminated electrically. The appearance of the building at night-time may well have been considered when the design was in its early stages and it is important that there should be contact with the architect in order to ensure the correct interpretation of the original concept.

It is necessary to decide on what should be considered the main direction

43


Figure 5.1. Sr. Martin’s in the Fields. Thc key fearures of this church havc been emphasised by floodlighting mountcd on the roof for the tower and floodlights mounted on the ceiling of the portico enable the columns to stand out in silhouettc. Metal halide floodlighting is used to contrast with high pressure sodium road lighring.

from which the building will be viewed. There may be one or two preferred positions. The location of the floodlights and lighting equipment must be considered in relation to the building and to the predominant view.

It is also necessary to decide for design purposes, on what should be considered as the normal distance between the viewer and the building, based upon the optimum direction of view. Whether an observer will be able to discern all or none of the architectural details on the facade will most probably depend on the distance involved, and on the modelling.

Often a tall building will be seen standing against a black night sky. If the immediate surroundings and background are also dark a relatively small amount of illumination will make the building appear much lighter and give it prominence. i f there are other buildings adjacent which are themselves illuminated, or if due to road lighting or signage, the ambient light values give an even greater impression of brightness, the illuminance incident upon the building facade will have to be of a relatively higher value in order to achieve an effective contrast between the building and its surroundings for it to have any worthwhile visual impact.

An alternative solution may be found by creating a contrast in colour rather than a contrast in brightness. The use of colour in floodlighting enables differences in planes and textures to be heightened, but as a general rule, colour should be used sparingly and with great discretion to avoid the result looking garish.

If floodlights are positioned parallel to the line of the building and aimed directly at the facade it is likely the lighting effect will be flat and disappointing. It is usually desirable to achieve fairly strong modelling on all but the plainest facade. A degree of modelling is obtained by ensuring

44


Figure 5.2. St. Paul's. The floodlighting of St. Paul's fulfills all the criteria for good modelling by limiting the use of floodlighting locations.

that the greater proportion of light arriving at the surface comes from a single direction, although the actual number of floodlights providing this flow of light may be many in number. The greater the angle between the line of view to the building and the direction at which the light incident upon the surface arrives, the stronger and more dramatic will be the modelling effect. The optimum effect is likely to be achieved when the direction of light flow is between 30" and 60° to the direction of view.

The complete facade should be illuminated to some extent in order to show the entire building outline to the viewer. This maintains the proportions of the architecture and allows the more prominent and desirable features to be given due emphasis. In any case the building needs to look more than just an illuminated front. Its solidity can be emphasised by adding light at a lower illuminance to the side, or at very least to the return corners, allowing the illuminance to decay gradually to the rear of the end wall. I t may be necessary to illuminate a sloping roof to achieve a coherent picture, otherwise chimney stacks may appear as if they are suspended in mid-air.

The view of a building may appear incomplete because lower areas of the walls or facade are partially concealed from a distance by trees or other larger structures. Trees and bushes may usefully be allowed to show up in silhouette against the building, or be provided with their own separate lighting arrangement in a contrasting colour. Alternatively, should the obstructions detract from the effect, the illuminance should be decreased in the lower areas of the building thereby diminishing the presence of silhouettes.

It may be found desirable in some instances to soften the strong modelling effect of uni-directional light. This may be achieved by illumination in the form of a fill-in light from a completely opposite direction to the main flow of light. In most cases it is likely that there will be sufficient ambient or inter-reflected light to give the desired result. Any fill-in light should be only one tenth the value of the main illuminance.

5.3.1 Relating practical considerations to specific characteristics

There are four basic forms which may serve to classify or describe the architectural style of a building facade.

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5.3. 7.7

5.3.7.2

Facades which are basically flat

Typical of buildings with completely flat facades would be many ashlar faced buildings, undecorated fronts of factory units and spec-built office blocks. Such dull functionalism without any projections or architectural detail are not ideal subjects for floodlighting. The achievement of any shadow effects may only be possible by placing the luminaires at exceptionally close-offset positions, unless for security surveillance a high level of uniformity is required, a certain unevenness in the brightness patterns across the facade could produce a degree of visual interest. This effect would be achieved by variations in placement and aiming of the floodlights. However if the surface has pitting or deep fissures, because the light gets absorbed you will not end up with an evenly lit surface. To overcome this one should position the floodlights closer together.

Facades with Strong vertical lines on a facade are characteristic of both medieval and predominantly verticd classical architecture. Many modern buildings have a strong vertical characteristics emphasis not only in their basic forms but in details such as pillars, support

columns or the sinews of the cladding framework for many modern office and hotel structures.

5.3.1.3 Facades with predominantly horizontal characteristics

5.3. 1.4

It is impractical to ignore such pronounced vertical influences and the style can be emphasised by applying illumination from the left and right sides of the facade using medium beam floodlights. Generally, due to the fairly light coloured surface material, the shadows formed by sharply oblique lighting are too strong and create too distinct a contrast. In-fill lighting from the opposite direction using wide-beam floodlights will attenuate the contrasts and soften the appearance. Visual impression is optimised when the direction of view is towards the areas of shadow, i.e. parallel to the flow of in-fill illumination. See Plate 18.

Post-war changes in planning and the introduction of new materials and construction techniques enabled the architect to exploit the full use of pre- stressed concrete forms and a wide variety of both vertical and horizontal cladding. A great many of the modern impressively high office and hotel blocks have a markedly horizontal emphasis. Often such design includes horizontal elements which project slightly, for example, window ledges or continuous bands that run across the facade from one side of the building to the other.

Floodlights placed close to the facade and aimed upward will produce bands of dark shadow above the projection. The wider the shadow band the more likely it will be that the surface area of the facade above the projecting ledge will appear to be floating on air and the building will appear as dis- membered sections.

Supplementary lighting may be placed upon the ledge to in-fill and eliminate the shadow, or alternatively, the floodlights have to be moved away from a close-offset position so that a greater distance exists between the facade and the light source.

Facades with external recesses

A facade is often designed to incorporate features such as balconies or galleries which may project forward or be recessed into the facade. In both cases the floodlights must be located some distance back from the building in order to prevent excessively dark shadows being formed. If lack of available space in front of the facade prevents this, supplementary illumination will have to be placed inside the balcony space or incorporated within the object creating the shadow. Supplementary light of a contrasting colour may be used to good effect in some circumstances.

The triangular pediments with sculptured compositions that dominate the entrance porches of some historic buildings should preferably be illuminated by floodlights located some distance away; linear sources positioned at the base of the triangle are seldom effective. Balustrading is

46


given prominence both when lighted by a line of fluorescent lamp luminaires mounted on a balcony and aimed outwards to give pleasing modelling of the baluster, and when revealed in silhouette against an illuminated wall. The appearance of a floodlit facade is enhanced if balconies, galleries with railings at the front, and similar recesses are illuminated individually, preferably by light which contrasts subtly in colour with that used for the main floodlighting.

Columned arcades and porticoes present something of a similar problem. Columns may be incorporated as part of the lighting effect by silhouette. Lighting concealed behind the columns may be used to illuminate the inner walls of the portico thereby silhouetting the columns against their background. The discreet use of colour in this situation may help to emphasise the effect. Columns that are relatively close to the facade are often revealed best by lighting them directly using floodlights which have a fan-shaped light distribution horizontally and with asymmetric distribution vertically. These luminaires would preferably be positioned at ground level, suitably protected, and aimed upwards at high angle.

In many open and enclosed areas people may be allowed to congregate in large numbers at times and places when there is insufficient daylight. The activities in these areas would normally be illuminated by electric lighting in accordance with recommendations given in this Guide.

When a building is floodlit light passes through the windows, so that they appear dark compared with the other surfaces of the building. Window lighting should, therefore, be treated separately, see Section 5.3.3.

Figure 5.3. Barclays bank. The architectural character of the building is enhanced by close offset floodlighting to the window bays and the gable. The floodlights have been carefully positioned so that they are unobtrusive.

When floodlighting a building, the decision must be taken as to whether it is the windows or glass within them which is more important architecturally. Except for stained glass, it is usually the window itself which is the more important element.

5.3.2 Modern buildings New materials and methods of construction have played a large part in developing the distinctive character of contemporary buildings. For example, the external and internal walls of modern steel-framed buildings are non-load-bearing and can therefore be made from lightweight materials and prefabricated before delivery to the site; reinforced concrete structures, some with roofs spanning 40 m or more, are also typical. See Plate 19.

Provided that the type of structure is suitable, floodlighting can be used to emphasise the social and architectural significance of many recently- erected civic, educational and commercial buildings. I t may also serve to advertise the products of the company that owns or occupies a building.

A characteristic of some modern buildings is that the exterior is intended to be an expression, a form of diagram, of the interior. For such buildings, floodlighting, however attractive the result might appear, may be wrong in principle; instead, the form of the building at night may be better expressed by controlled lighting of the interior, as discussed in Section 5.3.3. Floodlighting is also usually inappropriate if the building facade is flat and extensi.vely glazed. Where floodlighting is suitable the system should be designed to emphasise the salient features of the building.

Provision for any external floodlighting should preferably be made in the early stages of design. Wiring outlets and mountings for floodlights can then be incorporated in the building structure or provided at the necessary points in the surroundings; however, some flexibility is necessary to allow for final requirements.

Economics usually demand that building sites in the central areas of towns and cities are fully utilised, and consequently the forecourt of a building

47


may not be sufficiently large for floodlights to be installed within it. A close- offset system, with the floodlights mounted on the building, as in Figure 5.4, or in recesses, must then be used. Careful planning in consultation with the architect is necessary to ensure that the floodlights are so sited that coverage is adequate, shadows are not excessively distorted, and very bright patches are not produced on the facade adjacent to the floodlights.

Figure 5.4 Building mounted floodlight.

5.3.2.7 Colour

5.3.2.2 Essentials

5.3.2.3 Refinernen ts

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If the height of a floodlit high-rise block is accentuated by reducing the brightness progressively towards the top, it may be worth considering whether the building should be ‘capped’ with light, perhaps of a colour different from that used for the main floodlight.

Some modern buildings are raised on columns and have an open paved area at ground level for car-parking or pedestrian access. If the building is floodlit, the structural ceiling above the paved area and the supporting columns should also be lighted to provide an illuminated base otherwise the building may appear to be floating incongruously in space. Features can also be picked out with neon tubing or ‘lossy’ fibre optic tubing. This can be very garish or beautiful.

Attractive effects are sometimes achieved by using light of different colours at different times of the year. For example metal halide lamps can be used in winter their bluish-white light suggesting the cold season; in summer, high pressure sodium lamps can be used to give an appropriate impression of warmth.

It is important to remember that the colour of surface material is accentuated if light of the same colour is used. Alternatively, if white light from tungsten halogen is used this may be converted to colour by using filters. The following table gives the factors by which the calculated illuminance based upon white light, has to be increased in order to achieve the same value. These factors take into account the fact that coloured light is more conspicuous.

Table 5.1 Multiples of illuminance required with coloured filters

~~~~ ~~

Filter Illuminance multiplier colour factor

Amber I .5 Red 2.0 Green 4.0 Blue 6.0

There are certain essentials that should be an integral part of the design specification, although some aspects may only be checked on site prior to the commissioning of the installation.

No light trespass should be caused.

0 No glare should be apparent to road users, to the occupants of nearby buildings, or to visitors to the building floodlit. There should be no confusion with transport signalling or navigation. There should be no danger to the public from inconsiderate placing of floodlights, cabling and control gear boxes, and all electrical and lighting equipment should be vandal resistant, mechanically, electrically and thermally safe. Floodlights and cable should be as discreetly concealed as is practical.

Check the internal lighting or curtaining. See if it can it be organised differently to improve the overall effect, or to avoid spoiling the exterior effect.


There may be good reasons why it has not been possible to conceal floodlights from view and every effort should be made to ensure there are no objectionable highlights caused by excessive patches of brightness or bright objects close to the luminaires.

0 Check that the building appears as a coherent whole; that there are no floating chimneys or towers.

0 Check that the control and switching systems operate correctly.

5.3.3 Windows Windows are important features in architectural design both functionally and aesthetically. Usually they are lit together with the rest of the building although dramatic effects can be obtained by lighting the windows alone. With general floodlighting, especially close offset, care must be taken to avoid unwanted shadows being cast upwards by ledges. These shadows can be reduced or avoided altogether by mounting small floodlights or sealed fluorescent troughs on these ledges. The luminaires should be as discrete as possible. It is preferable to paint them the same colour as the surroundings. Sometimes they can be hidden behind mouldings or balustrades. They should have a wide angle asymmetric vertical beam with a sharp run-back above its peak. Since they are aimed upwards they should be completely waterproof. See Plate 21.

If fluorescent tubes are mounted on a continuous ledge close to the surface they light, care must be taken to reduce the gaps between the tubes to a minimum to avoid dark patches.

Another method of lighting windows is to light from within. Battens can be mounted at the top and bottom of the window. Light is reflected from the pale curtains or blinds. The appearance of these should harrnonise, in brightness and colour, with the floodlit facade. Windows in a building that is not floodlit may be revealed attractively by this form of lighting. Care must be taken that the building users ensure that all the blinds or curtains remain in position otherwise a patchy unsightly appearance can result. Alternatively, the lighting of the interior itself can be designed with a view to the night-time appearance from outside.

5.3.3.7 Sfained glass windows Coloured glass windows can present difficult, in some cases insoluble, floodlighting problems. If the window is to appear lit from inside the building as well as from outside and clear coloured glass is used, very little can be done.

In Figure 5.5 (a) the light from floodlight A passes straight through the clear glass with little or no scatter so that the window will appear dull or black from positions on either side. The floodlight at B will be seen directly through the glass, the rest of the window remaining dark. If a single light- source is used at A an image of the window will appear on the surface of any overhang or mall ceiling marked C, assuming that this is reasonably light- coloured.

Figure 5.5 Staincd glass window lighting

In Figure 5.5 (b) diffusing glass will scatter the light from a floodlight at position A, its apparent brightness depending upon the degree of diffusion. Position B is still unsuitable as the degree of diffusion is unlikely to be such

49


Effect wanted Consider

5.3.4 Spires and towers

Model I i ng Principal views

that the source image is completely obliterated. Owing to the angle of incidence of the light on the surface of the glass and the consequent losses by reflection, absorption and diffusion, only about 5% of the light falling directly on the windows will be effective. Consequently direct floodlighting of stained glass requires the use of very high output equipment with good colour rendering sources.

Colour

In Figure 5.5 (c) light coloured surfaces inside the room, or screens placed behind the window are lighted by floodlights placed in either position to give the effect of a lighted window without the use of a diffusing medium against the glass. General interior lighting can produce a similar effect if the walls and ceilings have a reasonably high reflectance.

Direction of Location of

It is almost always necessary to experiment on site to achieve successful results, but in spite of the difficulties, lighting stained glass windows can, with care and patience, produce some striking effects.

flow of light

Towers, steeples and domes appear as more naturally solid features when illuminated from only one direction, and not saturated with light all round. An impression of greater height is obtained by diminishing the value of illuminance progressively from the base to the top.

floodlight

Richly decorated spires are usually shown to best advantage when floodlit from the main structure of the building, the resulting patterns of light and shade are, in general more pleasing than those produced by floodlights located on distant buildings. It is sometimes necessary to use both systems to achieve the best effect. Lanterns in spires can be illuminated effectively by internal lighting. Pinnacles, crockets and similar features should be high-lighted by narrow-beam floodlights mounted nearby; a similar method can be used to reveal the decoration of ornamental brick or stone chimneys.

Having decided on the floodlighting effect required from key viewing positions and thus where the light should come from in order to achieve the

5.3.5 Design stages and considerations

Surface reflectance Calculate the I I I u in i no nce

I Select equipment I

Re-larnping

Set-up aiming of floodlights

I Check coverage

I

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I Commission system I Figure 5.6 Flowchart of design stages

T H E OUTDOOR ENVIKONMENT

5.4 Emergency lighting

5.4.1 Escape lighting requirements

5.4.2 Escape route signs

best modelling results, the more practical aspects of the floodlighting design have to be resolved.

The flow chart in Figure 5.6 identifies the major steps and considerations.

Data on floodlighting luminaires will be found in Section 6.2. The design process for calculating floodlighting schemes is fully detailed in Appendix I .

It should be noted that the illuminance required to achieve certain brightness contrasts on the facade depend upon a number of factors:

building surface material reflectance; 0 district brightness;

location of the building relative to the general surroundings; and the- dimensions of the building.

Facades, or even selective areas of surface material that may only achieve reflectance values less than 20% generally cannot be floodlit economically and it may be more practical to accentuate a section of bright trim with good reflectance rather than attempt to make dark stone appear visually bright.

Table 5.2 Reflectances of common building materials in fairly clcan conditions

Material Reflectance

White marble, white or crcam terra cotta, white plaster 0.80-0.70 Plain concrete, light grey or buff stonework 0.65-0.45 Medium limestone, sandstone, common tan brick Common red brick, sandstone, dark stonework

0.45-0.20 0.25-0.10

In many areas people may be allowed to congregate in large numbers at times and places when there is insufficient daylight. The activities in these areas would normally be illuminated by electric lighting in accordance with recommendations given in this guide.

However, to cater for the occasion when the supply to the normal lighting fails emergency lighting should be installed. The role of emergency lighting is to provide reassurance, avoid panic and to reveal fire alarm call points, fire fighting appliances and to illuminate the escape route for safe and rapid evacuation. BS 5266‘” lays down the standards for requirements and CIBSE Technical Memoranda T M 12: Emergency Lightink7’ provides advice on the design and selection of systems.

Although BS 5266“’ provides detailed requirements it is advisable that before the finalisation of specification is completed consultations are held with the local enforcing authority.

In general, covered areas such as shopping malls, subways, car parks, bus and railway stations and recreation centres are used by persons who will not be familiar with the layout of passageways. Therefore for safe and orderly evacuation suitable emergency lighting is required. It is necessary to provide strategically placed signs permanently indicating the ways out of the areas and to provide adequate illuminance on the escape route. Special care must be taken during the design to ensure adequate visibility of stairs, changes of direction and level.

It is very important that exits and emergency exits are quite clearly sign- posted and are visible at all material times. Such signs should be illuminated at all times with normal or emergency lighting systems. The signs should

51


use the preferred terms EXIT or EMERGENCY EXIT. Where direct sight of an exit is not possible and doubts may exist as to its position, then direction signs with an appropriate arrow or words should be added. The sign must direct someone who is unfamiliar with the layout to the nearest exit.

The signs must comply with requirements of BS 5499 Parts 1,2 or 3 and in one building should be uniform in colour, format and style. The signs should be mounted above exit doorways or an escape route at a height of 2- 2.5 m above the floor. The signs may be externally or internally illuminated. The use of self-luminous signs is recommended where maintenance is difficult, but note that self-luminous signs have finite life.

The externally illuminated signs with lettering of 50-75 mm high should be illuminated to at least 5 lux. Internally illuminated signs with opaque or translucent lettering of 75-125 mm high need a luminance of 30 cd/m2 for the translucent letter or surround.

5.4.3 Escape route In these covered and enclosed spaces there are three types of areas to be illumination considered for the purpose of escape lighting requirements. These

requirements presently are explained below.

5.4.3.7 Clearly defined route This is a corridor or a gangway. The horizontal illuminance at the floor on the centre line of a clearly defined route should be not less than 0.2 lux and 50% of the route width up to 2 m wide should be lit to a minimum of 0.1 lux with a uniformity of 0.025. Wider routes should be treated as several 2 m bands.

5.4.3.2 Large open areas These are malls, halls, concourses, car parks, and recreation areas. They will not have defined routes. The average horizontal illuminance over the whole area on an unobstructed floor should be not less than 1 lux with a uniformity of 0.025.

5.4.3.3 Stepped areas These are terraces, stadia and viewing galleries which are constructed as a series of steppings, the average horizontal illuminance on the nosing of the steps should not be less than 1 lux with a uniformity of 0.025.

5.4.3.4 Areas having fixed seating

These places will have fixed seating layouts on horizontal or sloping planes but divided by gangways which are designed as clear escape routes and should be treated so. For any part of the area having a fixed seating layout the average horizontal illuminance measured on a plane 1 m above floor/ pitch line, should be not less than 0.1 lux with uniformity of 0.025.

5.4.4 Operational conditions

5.4.5 System choice

5.4.5.7 Central power

The emergency lighting must reach the required illuminance within 5 seconds after failure of the supply of the normal lighting and should remain and maintain these levels for a period of not less than 1 or 3 hours as the requiremeqt in the British Standard"'. The emergency lighting luminaires should be chosen with care and be installed in locations where they will not cause disability glare (dazzle). They must have suitable protection against damage by impact and entry of dust and moisture.

It is well worth remembering that life depends on emergency lighting and therefore only reliable and safe equipment meeting the current British Standard'') should be considered for use. Basically two systems can be considered for use. Central power or self contained.

In a central power system the energy is provided by batteries or generators and the output is distributed through sub-circuits to feed a number of luminaires. Typically with a central battery system the battery room or cubicle will contain the charger, batteries, controls and indicators, and the automatic change-over switches. The wiring between power source and luminaires must be routed and protected by special means to ensure

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5.4.5.2 Self-contained

operational integrity for the full working duration even under fire conditions. Central systems tend to be cheaper (depending upon the size of the installation) to purchase and maintain but are complex to install and extend. The luminaires may use incandescent or fluorescent lamps.

In a self-contained system the emergency luminaires are self powered and operate the luminaire independently in an emergency. Each luminaire is fully equipped with a battery, charger, charge indicator and change-over device. The batteries are continuously charged via the normal unswitched lighting circuit and provide the local detection function. Self-contained luminaires tend to be expensive with limited operating temperature but are easy to install and extend and require little maintenance.

5.5 Security lighting With statistics showing marked increases in the incidence of crime and anti- social behaviour it is unlikely that we will ever experience the luxury of not having to protect our property and person against criminal activity of one form or another, be it from a petty opportunist, malicious vandal, or highly talented professional.

Although many crimes are committed in broad daylight it has to be accepted that the risk of criminal activity occurring is significantly higher during the hours of darkness and this is also confirmed by statistics.

5.5.1 Physical barriers An installation of lighting on its own must not be considered to constitute a system of security. The first line of defence must always be the physical barriers, walls, fences, gates, doors, bars and locks, all items necessary to slow down the process of unwanted intrusion, and which are usually associated with perimeter security. Given that a building is not situated within a protected area, then it is important that the outer envelope of the building has to be considered as the perimeter.

5.5.2 Supervision

5.5.3 lighting

5.5.4 Objectives

Crimes committed during the hours of daylight usually rely on a general level of normal activity for cover. During the hours of darkness when there are substantially fewer people about, the risk of detection is considerably lower. Security systems should be complimented by supervision from people such as permanent established employees, members of a professional security company, police officers, caretakers, wardens, neighbours.

Lighting can make the other security components more effective during the hours of darkness. I t removes the cover of darkness denying the potential criminal the valuable time needed to penetrate the physical barriers. Unable to properly conceal himself, the intruder’s confidence is significantly reduced and should he decide to ignore the lighting he undoubtedly risks failure, identification and capture.

Interference with the lighting system will also advertise his presence as this act of removing sources of light will still leave him vulnerable to detection.

Wherever possible the arrangement of luminaires should ensure that the system achieves a good measure of concealment for the security officers in their patrol surveillance work. A deliberate manipulation of the geometry of the installation to achieve a predominant flow of light based on angles of view is an extremely effective technique of security lighting. The discreet placing of luminaires will provide security staff with excellent visual conditions to observe sensitive areas safely from strategic viewing positions.

There are two basic objectives for security lighting.

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5.5.4.7 Light to act as a deterrent

An installation of lighting should be devised so that a potential intruder will feel that any criminal act will be difficult to perpetrate without a very high risk of being detected. In some instances lighting used for a different purpose can also be used to aid surveillance.

5.5.4.2 Lighting to assist This involves arranging a system of lighting so that should an intruder gain access to a building or area he may be revealed and identified and preferably captured safely and swiftly. This is important, for a failed attempt at burglary can prompt an intruder to resort to vandalism.

detection

5.5.5 Elements of the lighting system

A comprehensive system of security lighting has to concern itself with five elements: 0 perimeter, including grounds;

. access points which may be primary or secondary; 0 general areas;

building and structures; and 0 tactical lighting such as passive infra-red.

The design and construction of the perimeter and the location of the site itself must all be considered for the design brief. Influencing factors affecting the overall risk of attack would include the site’s proximity to a canal or waterway, to a railway or public footpaths, and to the ease of access an intruder may have from adjoining property, neighbouring buildings or residential estates and from large stretches of open land.

Examples of the application of security lighting to industrial premises are dealt with in the CIBSE Lighting Guide: The industrial environment‘2’. Lighting to aid security for commercial and residential premises generally need to be more subtle and the premises and sites may have totally different characteristics to protect and illuminate.

5.5.6 Offices, public These buildings are representative of the broad spectrum of premises which require security lighting. By their diversity of use they all present different sets of risk, Personal attack, burglary, vandalism and arson are probably the traditional risks common to them all. The primary objective must be to prevent an intruder gaining access and, therefore, any system of lighting must ensure that all access and exit points are illuminated. It may be of benefit to the overall scheme to identify the likely target areas, for example drug storerooms and pharmacy buildings in a hospital or duty free stores in an airport or hotel, and then to ensure that windows, doorways and any emergency escapes which connect or are adjacent to the high risk areas are protected by a1l;night lighting.

Monitors and roof-lights present security problems and are difficult to protect. Consideration should be given to providing lighting acrcss the roof froin appropriate locations.

buildings, schools, colleges, hospitals, hotels

Large office complexes, hospitals, colleges and universities are multi- building sites and the exterior security lighting should be planned in a logical and systematic pattern, i.e. as a potential intruder would consider, from the outside to the target.

Consider how the following features may be used to create difficulty to the intruder. 0 The perimeter, and what it is. A boundary fence, hedge, wall.

0 The landscaping. 0 The access points, entrances, exits, windows, roof lights.

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5.5.7 Retail premises

Routes between buildings patrolled by security guards need strategically positioned lighting. Ideally, the guard should never be required to check a dark, unlit area with a hand torch. This may involve using some luminaires controlled by passive infra-red switching in corridors and staircases and in rooms containing valuable records or equipment. Often the exterior lighting can be directed toward the building facade. A person may then be observed either as an illuminated figure or silhouetted against a brighter background. This is particularly useful if observation has to be done from a distance away.

The most obvious targets for both the deliberate and the opportunist intruder are the sales areas and storerooms which contain high value stock, and particularly if the goods have a ready market and are easily disposed of.

Protective lighting should be concentrated on the access points and those interior areas that can be observed from outside the premises. All doorways should be well illuminated evenly to avoid shadows that can provide temporary concealment, whilst internal lighting on the first floor with uncovered glazing will reveal the movement and activity of intruders. Lighting not operating or curtains drawn should arouse suspicions.

Light which falls upon the shop doorway from local street lighting may appear to be fortuitous but will create unwanted shadows in a vulnerable part of the premises. If the doorways are deep set, or if there is inadequate street lighting a suitable luminaire should be placed to illuminate the door entrance. The luminaire should be of vandal resistant type and preferably inaccessible. It could be mounted in a soffit above the doorway or even form part of the internal window display lighting with specific units directed outwards to flood the entrance area with light. This also helps put off ‘dossers’; sleeping in a well lit doorway is more difficult. These luminaires should be separately controlled from the normal display lighting, possibly by electronic photo-cell.

If 24 hour use is contemplated, display lighting of the high pressure metal halide type should be considered within the sales area, providing illumination from the rear to be seen from outside. Once inside the premises goods have to be removed from stock-rooms or displays and lighting will reveal the theft in progress. I t is important not to have lights which glare and reduce visibility down the sales area. Sources hidden from view or reflected light as from an uplighter give the most effective result. Transfer of stolen goods may involve the rear of shop premises, particularly if there is an enclosed loading area or vehicle yard.

A solid perimeter wall may look good but provides excellent concealment from view. Protection may be better by high quality link fencing which does not screen activities on either side.

Lighting within the loading area should be positioned to assist night-time security as well as providing light for working. Windows at ground level and access doors should be protected by grilles or shutters and these should be illuminated from within so that anyone attempting to force the grille or shutter is immediately framed in view.

Surfaces of the ground and walls should be as light in colour as is possible. A light plain concrete ground surface helps to reflect a large proportion of the light falling upon it and provides enhanced contrast to perceive the movement of figures in the area.

Windows at first floor level should receive some form of illumination as an added component of risk management. If the target is sufficiently tempting the deliberate intruder may well consider the use of a van roof as a means of gaining access to the windows.

55


should not only allow pedestrians to find their way about and to see obstacles in their path, but should also discourage crime directed at I

I

The need to provide suitable screening to control glare or avoid light annoyance cannot be overlooked. In these instances it may be possible to combine a smaller proportion of all-night discharge lighting with tungsten lighting operated through a passive infra-red sensor which is only activated when a person approaches the zone surveyed by the unit.

Manufacturers produce illuminance data in a format which enables quick

5.5.8 Open spaces Car parks, recreation grounds, school and college sports grounds and landscaped areas may well attract anti-social behaviour of one form or another. A floodlighting installation could be an effective deterrent and substantially reduce the fear of incidents occurring.

5.5.9 . Security lighting for The Home Office Crime Prevention Centre have promoted the use of light in its fight against crime activity. the home

Exterior lighting around the house should remove the 3-4 m of deep darkness that generally surrounds the property and remove the uncertainty and apprehension that most experience when a caller to the door is unable to be identified.

Among the standard crime prevention measures normally recommended by the Crime Prevention Officer is the fitting of a door viewer. During daylight this is a very effective addition to home security but after dark without a porch or entrance light correctly positioned it is not possible to discern features or even identify callers through the viewer. Correctly placed near the front door, a luminaire should illuminate callers while allowing the householder to keep back out of the light. It should be mounted on the wall but not so high that the caller is actually standing in a shadow.


at either edge of the illuminated area, see Figure 5.7 (a) or with an inset of 2 m on either side (Figure 5.7 (b)) to allow for a pedestrian walkway.

For a given lantern, a separate table is produced for each lantern arrangement, for each mounting height and for each lamp type.

5.6.1 Use of the The initial step in the design of a scheme i s to decide on the classification category of the area to be illuminated. A likely lantern, mounting height and arrangement are chosen and the appropriate table of data selected.

illuminance table

Take for example the case of a road 6 m in width, with 2 m pavement at either side, which requires illuminating to category 3/2 with the lanterns mounted at a height of 6 m over the kerbs. A source with a reasonable colour rendering is required and the 70 W SON-T lantern of Table 5.3 is deemed suitable.

The total width of the illuminated surface is 10 m (i.e. 2 X 2 + 6). As the lanterns are mounted over the kerbs, the inset is 2 m, see Figure 5.7 (a). Read down the column for a 10 m total width with a 2 m inset and select the largest spacing in Table 5.3 which still meets the illuminance requirements of category 3/2 given in Table 4.2. For this example, the required spacing is 24 m.

If the lanterns were mounted at the back of the pavement, then the zero inset column of data would be used, and the resulting spacing would apply to any width of pavement.

Table 5.3 Typical table of illuminances for 70 W SON-T lantern

Width of illuminated surface (m) 9 10 11 12 13

Lantern inset (m) 0 2 0 2 0 2 0 2 0 2

Spacing (m) avc min ave min avc min ave rnin ave min ave min ave min avc min ave min ave min

10 I 1 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

23.0 12.8 30.3 13.9 21.3 11.7 28.1 13.0 19.7 11.0 26.2 11.7 18.3 10.4 24.5 10.5 20.9 10.8 27.6 11.9 19.4 9.7 25.6 10.9 17.9 9.1 23.9 9.7 16.7 8.5 22.3 8.6 19.2 9.3 25.3 10.2 17.7 8.3 23.5 9.3 16.4 7.7 21.9 8.1 15.3 7.1 20.4 7.0 17.7 8.1 3.3 9.1 16.4 7.0 21.7 8.2 15.2 6.4 20.2 7.0 14.1 5.9 18.9 5.9 16.5 7.1 21.C 8.2 15.2 6.0 20.1 7.3 14.1 5.4 18.7 6.2 13.1 4.9 17.5 5.1 15.4 6.3 20.2 7.4 14.2 5.2 18.8 6.6 13.1 4.6 17.5 5.5 12.2 4.1 16.3 4.4 14.4 5.6 18.9 6.5 13.3 4.5 17.6 6.0 12.3 4.0 16.4 4.9 11.5 3.5 15.3 3.9 13.5 4.9 17.8 5.9 12.5 3.9 16.6 5.4 11.6 3.3 15.4 4.4 10.8 2.8 14.4 3.4 12.8 4.4 16.8 5.2 11.8 3.4 15.6 4.8 11.0 2.8 14.6 4.0 10.2 2.3 13.6 3.0 12.1 4.0 16.0 4.7 11.2 3.0 14.8 4.3 10.4 2.4 13.8 3.7 9.7 1.9 12.9 2.7 11.5 3.7 15.2 4.3 10.6 2.6 14.1 3.8 9.9 2.1 13.1 3.5 9.2 1.5 12.3 2.4 11.0 3.4 14.4 3.9 10.1 2.4 13.4 3.4 9.4 1.8 12.5 3.2 8.7 1.3 11.7 2.2 10.5 3.2 13.8 3.6 9.7 2.2 12.8 3.1 9.0 1.6 11.9 3.0 8.3 1.1 11.1 2.0 10.0 3.0 13.2 3.4 9.3 2.0 12.2 2.8 8.6 1.5 11.4 2.8 8.0 0.9 10.7 1.9 9.6 2.8 12.6 3.2 8.9 2.0 11.7 2.6 8.2 1.4 10.9 2.5 7.6 0.9 10.2 1.9 9.2 2.5 12.1 3.0 8.5 1.9 11.3 2.4 7.9 1.3 10.5 2.3 7.3 0.8 9.8 1.8 8.9 2.3 11.7 2.8 8.2 1.8 10.8 2.2 7.6 1.3 10.1 2.1 7.1 0.8 9.4 1.8 8.5 2.1 11.2 2.6 7.9 1.8 10.4 2.1 7.3 1.2 9.7 1.9 6.8 0.7 9.1 1.6 8.2 2.0 10.8 2.5 7.6 1.6 10.1 2.0 7.0 1.2 9.4 1.8 6.5 0.7 8.8 1.5 7.9 1.8 10.4 2.4 7.3 1.5 9.7 1.9 6.8 1.2 9.0 1.6 6.3 0.7 8.5 1.4 7.7 1.6 10.1 2.3 7.1 1.3 9.4 1.8 6.6 1.1 8.7 1.5 6.1 0.6 8.2 1.3 7.4 1.5 9.8 2.1 6.9 1.2 9.1 1.7 6.4 1.0 8.5 1.4 5.9 0.6 7.9 1.2 7.2 1.4 9.5 2.0 6.7 1.1 8.8 1.6 6.2 0.9 8.2 1.3 5.7 0.6 7.7 1.1 7.0 1.3 9.2 1.8 6.5 1.1 8.5 1.5 6.0 0.9 8.0 1.2 5.6 0.6 7.4 1.0 6.8 1.2 8.9 1.7 6.3 1.0 8.3 1.4 5.8 0.8 7.7 1.1 5.4 0.6 7.2 1.0 6.6 1.1 8.7 1.6 6.1 1.0 8.0 1.3 5.6 0.8 7.5 1 . 1 5.2 0.6 7.0 0.9 6.4 1 . 1 8.4 1.5 5.9 0.9 7.8 1.2 5.5 0.8 7.3 1.0 5.1 0.6 6.8 0.9 6.2 1.0 8.2 1.3 5.7 0.9 7.6 1.2 5.3 0.7 7.1 1.0 5.0 0.6 6.6 0.8 6.1 1.0 8.0 1.2 5.6 0.8 7.4 1.1 5.2 0.7 6.9 0.9 4.8 0.6 6.4 0.8 5.9 0.9 7.8 1.0 5.5 0.8 7.2 1.0 5.1 0.7 6.7 0.9 4.7 0.6 6.3 0.8 5.8 0.9 7.6 0.9 5.3 0.8 7.0 0.9 4.9 0.7 6.6 0.8 4.6 0.5 6.1 0.7

17.1 9.9 22.9 15.6 8.4 20.9 14.3 7.0 19.1 13.2 5.8 17.6 12.2 4.9 16.4 11.4 4.1 15.3 10.7 3.4 14.3 10.1 2.7 13.5 9.5 2.3 12.7 9.0 1.9 12.1 8.6 1.5 11.5 8.2 1.2 10.9 7.8 1.0 10.4 7.4 0.9 10.0 7.1 0.8 9.6 6.8 0.8 9.2 6.6 0.7 8.8 6.3 0.7 8.5 6.1 0.7 8.2 5.9 0.6 7.9 5.7 0.6 7.6 5.5 0.6 7.4 5.3 0.6 7.2 5.2 0.6 7.0 5.0 0.5 6.7 4.9 0.5 6.6 4.8 0.5 6.4 4.6 0.5 6.2 4.5 0.5 6.0 4.4 0.5 5.9 4.3 0.4 5.7

9.9 8.0 6.4 5.3 4.5. 3.6 3.3 2.8 2.4 2.1 1.8 1.6 1.5 1.4 1.3 1.3 1.2 1.2 1.2 1.1 1 .o 0.9 0.9 0.8 0.8 0.7 0.7 0.7 0.7 0.6 0.6

57


5.7 Landscape lighting

6 Equipment

6.1 lamps

Table 5.3 is calculated for a maintenance factor of 1.0. For other values, a correction needs to be applied. For instance, if the maintenance factor were 0.82 (i.e., for an IP54 lantern with a 36 month cleaning cycle in an area of medium pollution), the required illuminances are divided by this value (i.e., 6 lux and 2.5 lux become 7.32 lux and 3.05 lux respectively). It will be found that, by looking down the same column in the table as previously, the spacing becomes 22 m. An additional correction arrived at by a similar method can be made if the luminous flux of the lamp is different to that on the table. For the above example, if the actual lamp flux output is 6.5 kilolumens, then the necessary illuminance criteria become 7.32 x (5.50/ 6.50) = 6.19 lux and 3.05 X (5.50/6.50) = 2.58 lux. I t should be noted that this correction only applies if the luminaire light distribution is unchanged.

In addition to scheme design, the data is useful for the comparison of lanterns. However, it must be emphasised that performance in terms of illuminance should not be taken as the single criterion for assessing a lantern. The iIluminance data should always be used in conjunction with glare control data to ensure that the maximum intensities specified by BS 5489 Part 3(4’ are not exceeded.

Landscape design implies a broad view of a scene and the arrangement of elements within this view. Design is based on the satisfaction of the needs generated by various outdoor activities..For example, many of the lighting aspects are concerned with circulation, from roadways, through a site to a car park and thence for pedestrians to a destination, suitably emphasised. Lighting may reveal the route from place to place with special regard to changes of level and other hazardous points. Lighting may also be used to evoke a response, such as enjoyment or delight, or a feeling of safety. Due weight must be given to practical matters, running costs, maintenance and vandalism. See Plate 20.

Many son et lumi2re performances have made the public aware of the potential of light for special effects at landscape scale. The designer may model form, create screening or clear a view to give due emphasis to points of interest or significance within the overall character of a locality. By night the landscape architect can use light to reveal objects selectively: by directional lighting he can emphasise modelling, and by modulating and composing the areas of brightness he can give a sense of depth and perspective to a scene. The approach used is applicable equally to the view of a town as to a parkland or a domestic garden.

A landscape design method is detailed in Appendix 2.

Data for the lamps most readily obtainable and most commonly used in outdoor lighting systems with which chis Guide is concerned are summarised here.

The lamp does not only provide light; it can influence the way in which the light is distributed by the optical system and it can also provide an intrinsic colour. The smaller the physical size of the light source the more accurately the distribution of light can be controlled.

The choice of a lamp for a particular installation may be influenced by the following considerations. 0 The general requirement that lamps comply with the recommendations

of the relevant British Standards.

58


5.7 Landscape lighting

6 Equipment

6.1 lamps

Table 5.3 is calculated for a maintenance factor of 1.0. For other values, a correction needs to be applied. For instance, if the maintenance factor were 0.82 (i.e., for an IP54 lantern with a 36 month cleaning cycle in an area of medium pollution), the required illuminances are divided by this value (i.e., 6 lux and 2.5 lux become 7.32 lux and 3.05 lux respectively). It will be found that, by looking down the same column in the table as previously, the spacing becomes 22 m. An additional correction arrived at by a similar method can be made if the luminous flux of the lamp is different to that on the table. For the above example, if the actual lamp flux output is 6.5 kilolumens, then the necessary illuminance criteria become 7.32 x (5.50/ 6.50) = 6.19 lux and 3.05 X (5.50/6.50) = 2.58 lux. I t should be noted that this correction only applies if the luminaire light distribution is unchanged.

In addition to scheme design, the data is useful for the comparison of lanterns. However, it must be emphasised that performance in terms of illuminance should not be taken as the single criterion for assessing a lantern. The iIluminance data should always be used in conjunction with glare control data to ensure that the maximum intensities specified by BS 5489 Part 3(4’ are not exceeded.

Landscape design implies a broad view of a scene and the arrangement of elements within this view. Design is based on the satisfaction of the needs generated by various outdoor activities..For example, many of the lighting aspects are concerned with circulation, from roadways, through a site to a car park and thence for pedestrians to a destination, suitably emphasised. Lighting may reveal the route from place to place with special regard to changes of level and other hazardous points. Lighting may also be used to evoke a response, such as enjoyment or delight, or a feeling of safety. Due weight must be given to practical matters, running costs, maintenance and vandalism. See Plate 20.

Many son et lumi2re performances have made the public aware of the potential of light for special effects at landscape scale. The designer may model form, create screening or clear a view to give due emphasis to points of interest or significance within the overall character of a locality. By night the landscape architect can use light to reveal objects selectively: by directional lighting he can emphasise modelling, and by modulating and composing the areas of brightness he can give a sense of depth and perspective to a scene. The approach used is applicable equally to the view of a town as to a parkland or a domestic garden.

A landscape design method is detailed in Appendix 2.

Data for the lamps most readily obtainable and most commonly used in outdoor lighting systems with which chis Guide is concerned are summarised here.

The lamp does not only provide light; it can influence the way in which the light is distributed by the optical system and it can also provide an intrinsic colour. The smaller the physical size of the light source the more accurately the distribution of light can be controlled.

The choice of a lamp for a particular installation may be influenced by the following considerations. 0 The general requirement that lamps comply with the recommendations

of the relevant British Standards.

58


The need to reduce running costs and conserve electricity by utilising light as efficiently as possible, and by using lamps of the highest luminous efficacy consistent with satisfying other requirements (e.g. those of acceptable colour appearance and colour rendering). The spectral distribution of the light needed to give the required colour effects. Where strong colours are required, a lamp that emits light of a predominant colour is normally chosen. Colour intrinsic to the light source is more efficient than that obtained by filtration. For example, if blue light is required then it is more efficient to use a blue mercury halide lamp than to transmit by filter what little blue light there is in a filament lamp. While only a limited range of colour is available in this way, it is advisable to investigate the possibilities before adopting an external filter system. The maintenance facilities available and the cost of servicing. In general, costs will be reduced if lamps of long life are used. Limitations on lamp size imposed, for example, by the size of enclosure, as in handrail lighting.

0 The conditions under which the lamp will operate. For instance at low ambient temperatures, tubular fluorescent lamps operate economically only if used in a fully enclosed luminaire and with a circuit that overcomes starting difficulties.

0 The need, as for son et lumiere presentations, to dim lamps to extinction.

Current data for lamps readily available in the UK at the time of publication of this Guide are presented in Table 6. I . Within each type there is a range of lamps available which differ in construction, wattage, luminous efficacy, colour properties, cost, etc. For exact details of the characteristics of a specific light source the manufacturers should be consulted or the LIF Lamp Guide‘”.

Table 6.1 Lamps

Lamp Lamp Construction and appearance Luminous Life Colour rendering Restrike Run-up Typical applications type prefix efficacy (hours) time time

lrttrrs ( I d W ) (min) (min) ~ ~~ ~ ~

Metal CSI An electric discharge in a high 84 1000 Good 0-10 1 Feature lighting - tall buildings. halide pressure mercury atmosphere Beam can be modified using reflector different front lenses. Used mainly

for long throw, narrow beam floodlighting.

with metal halide additions in a compact fused silica arc tube, contained in a sealed glass reflector bulb, PAR 64 type. Needs control gear.

Tungsten GLS A tungsten filament heared to incandescence in a glass envelope.

High MBF An electric discharge in a high pressure (HPL-N) pressure mercury atmosphere. mercury The arc tube is contained in a

glass envelope with a fluorescent coating. Needs control gear.

~ ~~

8-18 1000- Excellent 0 0 Decorativc lighting, small filament 2000 sizc gives good control. Narrow

symmetrical beam to wide dispersive distributions. Best where burning hours are short.

35-54 5000- Modcrate 4 2-5 Road lighting, area lighting, used 24000 where cool appearance is desirable

Metal MB1 An clcctric discharge in a high 66-84 4000- Good 4-7 2 Building and area floodlighting halidc pressure mercury atmosphere 12000 used where better colour rendering

or cool appearance is required. with metal halide additives in an arc tube. Sometimes contained within a glass envelope. Needs control gear.

Building and area floodlighting Metal MBII. An elecrric discharge in a high 80-89 3000- Good 8-20 2 halide (HPI) pressure mercury atmosphere 6000 used where fan shaped distribution linear and tight vertical beam control are

required. with metal halide additives in a linear arc tube, Needs control gear.

59


Table 6.1 Lamps (continued) ~

Lamp Lamp Construction and appearance Luminous Life Colour rendering Restrike Run-up Typical applications type prefix

letters

efficacy (hours) (Im/W)

time time (min) (min)

-.

Tubular hicF An electric discharge in a low 37-100 5000- Moderate to 0 0 More suitable for indoor than fluorescent pressure mercury atmosphere 15000 excellent outdoor lighting but valuable for

contained in a glass tube depending on the intcrnally coated with a properties of the fluorescent material. Needs fluorescent versions suitable as replacements control gear. coating. for tungsten lamps.

some types of precinct lighting and close offset floodlighting. Compact

High SON An elcctric discharge in a high 67-137 6000- Varies from poor 1 3-6 Building and area floodlighting, pressure pressure sodium atmosphere. 24000 togood road lighting, sccurity lighting. sodium The arc tube is contained in an depending on the Suirable for applications whcrc

ourer envelope. Needs control pressure used. warm colour appearance is gear. desirable. Recent developments

include one form with good colour rendering properties.

Low sox An electric discharge in a low 101-190 5000- Non-existent 0-10 8-12 Road lighting, security lighting. pressure pressure sodium atmosphere. 20000 Floodlighting of buildings that sodium The glass arc tube is contained in

a glass envelope. Needs control gear.

respond to monochromatic yellow light.

Tungsten T H A tungsten filament heated to 18-24 2000-4000Excellent 0 0. Small area and security. Similar to halogen incandescence in a small above but tubular sources give a

fan shaped distribution. envelope containing halogens.

6.1.2 Summary of light The broad properties of the light sources commonly used for exterior source characteristics lighting are summarised in Table 6.1, The meaning of each column heading

is as follows:

6,7.2.7 Lamp type and prefix letters

These may be found marked on the lamp or on its packaging and in the UK they are widely used as a means of identification. Additional letters may be added to the end of the prefix according to the construction of the specific lamp, e.g. F for a fluorescent coating, R for a reflector coating and T for tubular lamps. The prefix letters shown in brackets are widely used in Europe and may be found on equipment in the UK.

Basic arc tube filling

Operating pressure

Metal halide additives to arc tube P

M Mercury

6-High c-Low

(fluorescent tube)

Fluorescent phosphor coating on outer bulb

Lineor bare orc

Reflector bu I b

MBI MBlL MBlF

7 F

1 MBF MBFR

so Sodium

N-High

7-

SON SONR sox Figure 6.1 Discharge lamp designations

60


6.1.2.2 Construcfion and This column describes the method of light production and the physical appearance appearance of the lamp.

6.1.2.3 Luminous efficacy This is a measure of how efficiently the lamp converts electrical power (watts) to light (lumens). The higher the value of the luminous efficacy, the more efficient the lamp. A range of values is given for each lamp type because luminous efficacy varies with power. These values do not include the power consumed by any control gear that may be required.

6.1.2.4 Life

6.1.2.5 Run-up time

6.1.2.6 Restrike time

6.2 Luminaires

The life of a lamp will be affected by such factors as the switching cycle, the voltage supply and the physical operating conditions. The lives of tungsten and tungsten halogen incandescent lamps and metal halide and high pressure sodium discharge lamps, are particularly sensitive to the voltage applied. Within a range of lamps the life will vary from one wattage to another, generally the lower wattage lamps having the shorter life. It is

.always advisable to contact the lamp manufacturer for the data regarding the particular lamp under consideration. The range of lamp life given in Table 6.1 refers to the typical lamp’s life as defined by 50% of the lamps in a large installation failing. The lower value in each range, refers to the lower wattage lamps and the higher value refers to the higher wattages.

Tungsten, tungsten halogen and tubular fluorescent lamps produce significant amounts of light immediately when switched on. All the other lamp types require several minutes to approach full light output; this may be important where installations have to be used at unexpected times.

Tungsten , tungsten halogen and tubular fluorescent lamps can be switched off and then on again immediately. All the other lamp types, unless fitted with special control gear, show a significant delay after switch off before they will re-ignite. This property may have important safety implications as momentary interruption in the electricity supply can extinguish these lamps and it may be some time before they can be re-lit.

Manufacturers’ catalogues will give detailed descriptions of specific fittings, the principal characteristics and data of luminaires used in the outdoor lighting systems. Luminaires with which this Guide is concerned are summarised here.

The choice of a luminaire for a particular installation may be influenced by the following considerations.

The general requirement that luminaires and associated accessories comply with the recommendations of the relevant British Standards and quality assurance documents, 0 In choosing fittings for use outdoors, the design life of the installation

must be considered. The initial cost of equipment may be a small part of the total cost in use of the installation and the ease and frequency of necessary maintenance can greatly affect the economics.

0 The requirement that the daytime appearance of luminaires and columns should be in keeping and scale with the surroundings.

0 The mounting arrangements of luminaires vary but are usually related to the permissible burning position of the lamp. For example, tungsten halogen and low pressure sodium lamps which must be kept close to the horizontal will require the luminaire to be adjustable only about the lamp axis. Accurate aiming, if applicable, should be set up in the floodlighting system so that relamping and cleaning should be possible without disturbing critical settings. Ease of access to the lamp, the reflector, and the front glass for relamping and cleaning is also important.

61

6.2.1 General requirements


- I I , 1 1 1 1 1 1 1 I I 1 1 1 1 1 I I I I I I 1 1 1

131W

/

2000w

15W

I I I I 1 I , , , I I I I I I I I I I I I I I , I #

1 02 103 1 0 4 105 Lamp lumens

Figure 6.2 Light output comparison

Luminaires should comply with the requirements of the appropriate sections of BS 4533 Lurnin~ires'~) and be suitable for the conditions (e.g. outdoor or indoor) under which they will operate. BS 4533") classifies luminaires electrically according to type of protection provided against shock, and mechanically according to protection against atmospheric conditions ( e g rainproof, dustproof). For many applications, classification according to light distribution is also needed. The classification systems adopted in this Guide for floodlights are described in Appendix 1. The luminaires used for lighting covered areas are not classified conveniently

62


6.2.2 Mechanical characteristics

6.2.3 Floodlights

and manufacturers' data should be consulted. Street lighting lanterns used in some of the lighting systems dealt with in the Guide are classified in accordance with BS 5489(4).

The classification of luminaires identifying the degree of protection against ingress of water and dust is important in exterior lighting. The majority of floodlights, bulkheads and bollards have ratings between IP23 and IP65. However, there are other mechanical design considerations of importance in lighting systems, i.e. those affecting their installation, their aiming, and their maintenance, which depend on the particular application. For example the characteristics of a low wattage unit to be used for lighting features in a garden will be quite different to those provided on a high wattage narrow beam discharge projector intended to light railway sidings from a height of 30 m. Both types will probably be fully enclosed, but a linear tungsten halogen floodlight designed for general area lighting at low to medium mounting heights can be of an open design so long as such a unit is only directed downwards.

A range of symmetrical and fan shaped beams can be produced by suitable combinations of lamp, reflector and front glass. A narrow beam spread is provided by a source of small dimensions in a specular (mirror) reflector of precise contour. If a front spreader-glass is fitted to the floodlight, or the reflector contour or surface finish is suitably altered, a wider beam may be obtained only by using an impracticably large reflector. A linear source, such as linear tungsten halogen lamp, can be regarded as large in the plane containing its length and compact in the plane at right angles; lamps of this form are, therefore, useful for producing fan shaped beams, the narrow beam-width normally being in the vertical plane. Several beam shapes can often be provided from basically the same floodlight by varying the combination of lamp and reflector.

The optical characteristics of floodlights fall into three basic groups. These are identified by the general shape of the intensity contours on a graph with the angles from the beam axis in the vertical V and horizontal H planes. Figure 6.3 shows the general shapes of the three groups.

Figure 6.3 Typical light distribution, shown diagrammatically for a) syrnmctrical floodlight b) asymmetrical beam floodlight c) double asymmetrical beam floodlight

Within each of these patterns there can be varying degrees of spread of the light. This is described by some angular measurements of the beam defined as embracing all directions where the intensity of the floodlight exceeds 0.1 of the maximum intensity. The beam angle, indicating spread, is the angular, extent of the beam in the vertical and horizontal planes. For a symmetrical floodlight one figure suffices, e.g. 60° (or 2 x 30, implying 30°, on either side of the axis). For asymmetrical distribution two values are required, e.g. horizontal 100" and vertical 40". For a double asymmetrical pattern three values are required, e.g. horizontal 100" vertical above peak 20°, and vertical below peak 40' (or horizontal 2 x 50°, vertical 20" + 40').

Floodlights may be mounted on the ground and directed upwards, or mounted on a wall, or mounted singly on columns or in groups on mast towers, The design of the mounting stirrups or spigots must take this diversity of use into account and it is often more economic to design a

63


6.2.4 Area lighting luminaires

6.2.5 Luminaires for covered areas

6.2.6 luminaires for various uses

number of mounting accessories, which are used as required, rather than designing alternative mounting facilities into each standard unit.

A floodlight must be well constructed if it is to function for a number of years without trouble. Metalwork should be protected against corrosion, and luminaire parts which have to be removed for access to the interior should be properly gasketed to restrict the entrance of moisture and dirt. Trunnion and stirrup mountings and similar parts should be heavily galvanised.

Most of the outdoor areas that are within the scope of this Guide may be lit by decorative road lighting lanterns or by floodlights; use of the latter is discussed in Section 6.2.3.

Decorative lanterns are usually mounted either on columns or on building facades. .Many designs of lantern and column are available, and a combination can be chosen to meet the technical and aesthetic requirements of a particular installation. Most decorative lanterns have a light distribution in the vertical plane that is substantially symmetric; photometric data for a particular combination of lamp and lantern can usually be supplied by the manufacturer. Impact-resistant enclosures are available for some types of lantern and can be used where their relatively high cost is justified by the risk of repeated breakage.

The covered areas included in this Guide are normally lit by a suitable type of standard interior lighting luminaire. Surface-mounted or recessed luminaires with prismatic or diffusing enclosures are suitable for many applications. The luminaires used under outdoor canopies and in other partly exposed locations should be weather-proof and suitably protected against corrosion.

Bollards, bulkheads, insets and well-glass luminaires accommodating incandescent, compact fluorescent or high pressure discharge lamps are used for lighting many subways, walkways, stairs and steps. These various types of small luminaires are often within hand reach and consequently provide attractive targets for vandals. They should, therefore, be strongly constructed, fitted with an impact resistant cover, and have an anti-tamper fixing arrangement. Where necessary, wire guards can be fitted to give extra protection.

Various other types of luminaire are used occasionally in the outdoor environment; descriptions are given in manufacturers’ literature.

All luminaires breathe, allowing fine dust to enter and settle on the inner surfaces of the luminaire and on the lamp, and for this reason a sealed beam lamp has an advantage. Mirror glass reflectors deteriorate chiefly because heat affects the backing to the silvered surface. Today, these have largely been superseded by electrolytically brightened and polished aluminium reflectors, anodised for protection against corrosion. Reflecrors of this type are normally not replaceable.

All moving parts should be greased regularly to prevent seizure. The adjustment nuts and bolts of floodlights that are to be mounted high on buildings or columns should be captive to prevent loss or an accident during servicing.

The oscillation and twisting of columns and masts in high winds will cause the luminaires to vibrate, and devices may be needed to prevent lamps working loose.

64


6.3 Control gear

6.4 Supports

6.4.1 Columns

The control gear which is associated with all types of discharge lamps should fulfil three functions.

Start the lamp even at low temperatures.

Control the lamp current after ignition.

Correct the power factor.

Control gear consumes energy. The efficiency of a lamp circuit as a whole depends on the total power taken by the lamp and the control gear. It is also necessary to consider the power factor of the circuit in order to minimise electricity charges and to ensure correct cable ratings.

The current and the wattage ratings of cables, fuses and switchgear used in the control gear must be related to the total current in the circuit, or an allowance may be necessary for increased initial currents and voltages during switching. Harmonic currents may be present and will increase the neutral current in a three phase system. Current ratings of neutral conductors should be the same as that of phase conductors. Manufacturers can supply information about the power factor and harmonic currents of their control gear. All electrical installations should comply with the current edition and amendments of the Regulations for Electrical Installations published by the Institution of Electrical Engineers.

It is important to appreciate that the lamp and the associated control gear constitute an integrated unit for producing light. Lamps from different manufacturers may not operate on the same control gear even when the lamps are nominally of the same type. Whenever any change is proposed in either element of the lamp/control gear package, care should be taken to ensure that the proposed combination is compatible, both electrically and physically. For some lamps which are sensitive to the voltage applied tapped chokes are provided. I t is important that the voltage at the point of connection is matched to the voltage tapping.

High frequency control gear is now widely available for tubular fluorescent lamps. This gear has a number of advantages over conventional control gear, the main ones being increased efficacy, instant starting and flicker free operation. It is of special interest for the outdoor environment because it is able to strike fluorescent lamps at low temperatures. Special types of control gear are necessary if dimming or rapid re-ignition of some types of discharge lamps are required, although some types of high frequency control gear can be used to dim tubular fluorescent lamps to a limited extent, without further modification.

The life of control gear is sensitive to ambient temperature. The control gear used should have an appropriate temperature rating for the situation. If this temperature is exceeded the insulating material may deteriorate rapidly.

Luminaires used in some outdoor lighting systems are mounted on columns or masts with a range in height of 4-30 m. At heights of up to 12 m there is a strong case for the use of columns; between 12 m and 30 m the choice depends on the quantity of equipment to be supported; above 30 m towers or heavy duty masts are used.

Until comparatively recently the majority of lighting columns were made of concrete or steel, but aluminium has the advantages of Iighter weight and a natural resistance to corrosion, even in atmospheres heavily laden with salt or chemicals. Aluminium, steel and concrete columns are generally available in 5, 6, 8, 10 and 12 m heights with provision being made to accommodate control gear, mounted on a wooden base-board, in a locked

65


6.4.2 Masts

6.4.3 Towers

6.4.4 Foundations

6.5 Control

compartment at the bottom of the column. The foot of a metal column is coated internally and externally with bitumen over the whole of the planted depth and to 50 mm above ground level. Columns above 12 my for example 16-20 m, are normally of the raise and lower variety. The column is hinged at its base and is raised and lowered by the use of a jack frame assembly. Many column designs are available and a type should be chosen that is in keeping with the surroundings.

When siting lighting columns near trees the following points must be considered: 0 easy access to maintain the installation e.g. for cleaning, painting and re-

lamping; and 0 problems arising from the future growth of the tree obscuring the light.

These are used extensively in large areas, such as docks and lorry parks at heights up to 30 m. The luminaires are mounted on a cradle with special raising and lowering gear consisting of a system of steel cables carried inside the mast and controlled by a portable winch at ground level. Masts above 50m are normally accessed by means of an internal ladder with the luminaires mounted on a headframe.

A lattice tower may be an economic alternative to a single mast, its aesthetic disadvantage being compensated by its ability to carry a greater number of floodlights and by the versatility of the various types of head platforms.

Adequate foundations are necessary, and all structures must be able to withstand the wind forces likely to be experienced. Manufacturers will usually provide information on foundations and data on the maximum safe weight and wind area of luminaire for each type of structure. This data can be compared with those for the luminaire it is proposed to use, and a check made that the system is within the safe limit; unless the manufacturers’ recommendations are followed, the column or mast may deform or collapse in high winds.

The simplest method of control is to have someone switch on the lights. But this assumes that: someone is available; he remembers when to do it; and he knows where the switches are located. The problem still remains of how to switch off at midnight, or at 3 am , or at dawn. The ‘simplest’ method is obviously not so simple and some form of automatic control is to be preferred.

Today, contrpl systems are an inherent part of any lighting installation. They can take many forms, varying from the simple wall switch to being part of a sophisticated microprocessor-controlled, building management system. Whatever the method used, the aim of a control system is always to ensure that the lighting system is only operating when it is required, and that when it is, it is operating in the required state.

One particular aspect of switching which has limited its use in the past has been the difficulty of switching individual or small groups of fittings without excessive investment in wiring. Recent development in electronics have made it possible to send switching signals by low voltage wiring or by high frequency transmission pulses over the existing supply wiring. Further logic circuitry now exists which allows individual luminaires to respond in one of several different ways. Such systems provide great flexibility in the way the lighting installation can be used.

The current emphasis on energy cost has led to the realisation of the losses

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Midnight

due to depreciation of lamps and reflecting surfaces and increased emphasis on regular maintenance. The cost-effectiveness of planned lighting maintenance schemes is increasingly emphasised by the increased cost of current and the need to maintain illuminance to avoid drops in output or efficiency due to inadequate lighting. Planned lighting maintenance is also well advised if fittings are mounted in awkward areas.

Midnight

A person should be made responsible for the monitoring of the lighting system and effect a lighting maintenance scheme of regular cleaning and group Iamp replacement (where appropriate) as well as the servicing and checking of the switching system. Specialist maintenance contractors exist, for installations with a large number of lighting points, to provide the necessary technical and operational skills as well as having the necessary access equipment, which otherwise would be purchased by the user and left unused for the majority of its life.

6.5.1 Automatic control (no n-i n tell igen t)

This can utilise inexpensive time clocks or photocells to switch/dim lights, A photocell can monitor the level of useful daylight and turn off fittings when daylight levels are sufficient. Automatic systems must normally have some degree of manual over-ride to cater for unexpected circumstances, and a time-lag must normally be built into the system to prevent premature switch off. The presence of personnel can be signalled by a proximity detector utilising infra-red, acoustic or radar techniques.

- Time PE cell PE cell Off 8am on

t Kmeswitchloff

+ Krneswitch on

Figure 6.4 Block diagram for switching pattern

While many users will. be satisfied by simple dark/light control offered by the photocell (PE cell), some organisations may not want the security lighting to come on during the winter before the premises are vacated in the evening or to stay on after they are reoccupied in the morning. In such cases a simple time-switch can be used in conjunction with the PE cell to energise the security circuit at the appropriate times. Figure 6.4 shows that only when both the timeswitch and PE cell are on are the security lights activated (shaded area). Thus in the summer months it would be restricted by the time-switch to outside working hours, while in the summer months it would be restricted by the PE cell to the hours of darkness, thus minimising the energy consumption and extending the calendar life of the lamps.

6.5.2 Automatic control Computer-based control systems are becoming increasingly popular. These rely on dedicated computers or processors to control the Iighting, as well as other building services.

(intelligent)

Automatic programmed control is sometimes used for son et lumihe presentations providing automatic changes of brightness, colour and direction of light by a pre-determined computer program.

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6.6 Electrical installation

The total electrical load demanded by the typical outdoor lighting installation used at locations such as hospitals, colleges and schools, and commercial areas, is likely to be quite small when compared to the maximum demand taken by the remainder of the complex. However, the capital cost of the outdoor lighting is likely to be considerably higher than that of the interior system in terms of cost per kVA installed.

Cabling costs for an outdoor lighting installation are expensive when compared to the per point costs for other parts of the total load; distance is the principal cost item and not the current involved.

The size and capacity of the electrical system, feeders, branch circuit layouts, switching and dimmer controls, must all be specifically selected and designed to conform to standards and codes in addition to the requirements of the lighting system for which they are intended to operate and control. This is to ensure that the rating of each cable is greater than that of the protection device that is supplying it and that the total volt drop is low enough to allow each light to operate correctly.

If the designer of the lighting system is not a qualified electrical engineer capable of designing and specifying the electrical wiring system, the services of a competent consulting engineer or electrical contractor should be obtained.

All electrical systems must be designed and installed in accordance with the provisions and requirements of the current edition of the wiring regulations of the Institution of Electrical Engineers.

It is practical at the outset to design for maximum flexibility and efficiency from the lighting system; service cabling for outdoor lighting purposes differs from the conventional power cabling for several basic reasons. 0 Total lighting load is known at the design stage. 0 The circuit carrying capacity of the cabling is normally in excess of the

system load, no allowance being made for diversity. Decisions which affect usage such as future extensions to the scheme involving increases to the load can be either foreseen and allowed for, or rejected as unlikely.

Once the total electrical loading required for the lighting system has been determined it is often beneficial to consider the division of this value into sub-loads which may then be further divided into individual sub-circuits each having a lighting panel adjacent to the centre of the lighting load it is designed to supply.

The magnitude, dperational requirements and complexity of the project will determine how many sub-loads may logically be justified, but the greater the number of circuits the more flexibility is given to control and switching.

Outdoor lighting installations can utilise a variety of supports and fixings.

Most new schemes will use new equipment, columns or towers, but often for reasons of cost particularly in rural areas, many new schemes have to be installed using existing columns or even wooden poles to support the lanterns or floodlights.

It is important to be aware of the fundamental dangers and responsibilities connected with electrical safety in the installation, commissioning and maintenance of both public and private exterior lighting as with other plant and equipment, on or adjacent to, the public highway or other public places.

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Much of the electricity distribution network, particularly in rural areas, is made up of overhead lines supported by towers or wooden poles. There are minimum statutory heights at which conductors can be erected, but it is difficult to address the question of minimum statutory heights because each regional electricity company (and possibly local authority) has different rules and regulations on this matter. It is advisable to refer to the distribution planning section at the regional electricity companies.

Low voltage overhead lines are normally supported on wooden poles which are durable and blend well with the environment. Most are redwood, spruce or Corsican pine treated with creosote or other chemicals to prevent decay.

Many types of premises receive electricity via an overhead service. Great care must be taken when using objects such as mobile cranes, ladders, or when manoeuvring columns into position near overhead lines or near to unshrouded cables going from the overhead line into the building.

If installation or refurbishment work has to involve being close to the overhead service, advice on the application of safe-working procedures must be obtained from the regional electricity companies.

When lighting systems are being installed, the responsible authority for the installation is also responsible for the safe conduct of the work and for ensuring that appropriate clearances from existing overhead lines are provided.

Where there is likely to be a clearance problem the regional electricity company will expect to be contacted for advice appropriate to individual situations. Where premises and land are supplied with electricity or are likely to be used for concealing a network of underground cable, utmost care must be taken if excavation work is necessary. Reference to the distribution planning section of the regional electricity company is recommended.

Since the late 1970s standard colours have been adopted for underground pipes and cables, these are given in Table 6.2.

Table 6.2 Undcrground cable colour conventions

Colour of cable Description

Black Electricity low voltage, these cables could be black PVC or black bitumastic covered in white hessian.

Blue Water. Green Cable tclevision. Grey Telephone. Red Electricity high voltage. Yellow Gas.

Cables laid beneath public highways are generally at an average depth of 0.65 m although obstructions and variations in ground levels that could have occurred since the laying may cause the cable to be located at a deeper or shallower position. Since 1983 there have been certain agreements that when cables are laid across good agricultural land which could be ploughed, they will have a cover depth of not less than 0.91 m, although this may still be varied by agreement.

Older cables and those in permanent pasture, pathways, farm roads, areas of hard standing etc. may be laid at shallower depths. Service cables at the point of entry to a consumer’s property are usually laid at a depth of 450 mm.

69


The regional electricity companies require a means of providing an electricity supply to all outdoor lighting installations, typically public lighting, plant and equipment adjacent to the highway, illuminated signs and floodlighting installations. The contractor, or authority responsible should provide a weather-proof enclosure such as a pillar, a column base or a pole-mounted box suitable to the regional electricity company for cable entry, termination and fixing of a cut-out. When the enclosure is within 3 m of the ground, or any platform or structure to which the public may have access, it is essential that the enclosure is locked with a tool or key in order to prevent as far as it is reasonably practical any unauthorised access. Within the enclosure should be a suitable consumer’s earthing terminal, preferably independent from the board’s earthing terminal, to which all exposed metal parts of street lighting columns or other types of metal supports should be bonded. The metal access doors of concrete or plastic columns do not require to be so bonded.

There are two methods of providing an electrical supply to these installations: combined neutral earth CNE; and separate neutral earth SNE. of the two systems, the most common method used for new supplies is the CNE system. This is a two conductor system where the supply neutral also acts as an earth continuity conductor and as such is required to be multiple- earthed. In this system, metal-work which is required to be earthed is connected via the earthing terminal to the neutral conductor at the supply point. Additionally, an earth electrode is required at the last or penultimate lamp column or other service point where a number of units are fed from the same distribution main.

The contractor, or responsible authority, for the project is responsible for ensuring that the cabling, equipment and control gear are correctly installed, commissioned and maintained, and comply in every respect with statutory requirements and acceptable standards, the Institution of Electrical Engineers’ current edition of the wiring regulations, and other approved codes of practice.

A matter of considerable importance to both the lighting and electrical aspects of all outdoor lighting projects must be the degree of interest and care shown for the preservation of the landscape environment. This need for care applies equally to the items of electrical equipment - i.e. the siting of a transformer, a sub-station or a diminutive service pillar - as to the perhaps more critical placing of columns, supports or individual floodlights.

In order to achieve a desired lighting effect which also demonstrates a concern for the landscape there has often to be a compromise between what constitutes the ideal location for a particular floodlight and what may be the most appropriate .position for the luminaire considering the relationship between the night-time effect and the daytime appearance.

It is now important in the light of legislation on quality assurance and product liability to ensure that each individual component is appropriate and operates satisfactorily and that the completed installation provides the desire.d effect. To do this it is necessary to subject the installation to a critical appraisal of test, setting-up and commissioning.

This must be considered as an important function within the completion schedule of the project and should not be confused with any independent evaluations which may be requested by the client or his representative as part of the final hand-over arrangement.

The commissioning of the outdoor lighting system should be the subject of a planned operation which involves the system designer, the electrical contractor and where appropriate any architect or project management

70


6.6.1 Tariff

team through whom the client may wish to be represented. The time required by the commissioning team will inevitably vary depending on the size and complexity of the installation but it is important to allocate an evening period of sufficient duration to permit investigation and, where appropriate, correction of any failures due to design, equipment, communications, installation or operation that are likely to be identified. Several evenings may have to be planned and allocated to budget.

Commissioning routines need to include checks on individual luminaires to ensure each is operating satisfactorily. Once this is established the complete lighting system can be set to operate and be adjusted where required. It is during these latter stages during the setting-up and final aiming of the floodlights that incorrect positioning or omissions in design will become apparent. For example, any incorrect choice of lamp type, colour filter or luminaire type will need correction. Incorrect design choices are often . created by failure to respond to changes in circumstances which occur during the design process.

Trial and error has always been considered a most rewarding task associated with decorative lighting schemes. Full commissioning must not be considered as being a trial and error type of exercise.

Every member of the design team connected with the project has a responsibility to advise on the visuaI aesthetics of a system, rather than simply the technical quality. Although technically brilliant, a daytime appearance which lacks harmony and consideration for the environment can produce unfavourable reactions among the local communities.

Concern for the landscape and the quality of the environment is of practical importance in promoting local approval. Every significant change in the use of a premises or land has to be approved by local planning authorities and most are now firmly committed to environmental issues. It is necessary to ensure that there is a continuity of relationship between the daytime and night-time image.

Where towers and masts or parapet fixings are likely to be viewed against an open sky or a particularly attractive rural panorama, any protective painting of the metal should be relatively light in colour or selected with camouflage in mind; generally strong saturated colours should be avoided.

Creative ways of concealing floodlights and control gear housings in a natural way using trenches, shrubbery, and trees or low fencing and walls, should be considered. If concealment is not practical, backgrounds should be chosen which reduce the daylight emphasis on the equipment. Electrical equipment which is likely to be greater in height, such as distribution boxes and supply pillars, should not appear visually stark and aggressive in the landscape view.

Privatisation of the electricity supply industry has brought about a situation whereby all regional electricity companies now offer different electricity tariff structures. It is important therefore that at the outset of the project a local tariff advisor is consulted. There are often unpublished tariffs that can be made available and customers can even negotiate their individual contract, for this reason it is recommended to contact the regional electricity company for tariff guidance as early as possible in the project, as this could incorporate advice on energy efficiency, load/system energy management systems, contracting and maintenance contracts.

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7 Maintenance

7. 1 Commissioning the With very few exceptions, successful outdoor lighting installations result from the unique blend of various lamp types operated in a variety of luminaires offering different optical systems, a wide range of control gear and equipment, a myriad of electric circuits, switching controls and mains supply cabling, all installed specifically to achieve and maintain a design level of performance.

system

Therefore it is unlikely such installations will be the work of just one person but usually will be the result of a combined team effort by specialists including architects, planners, lighting designers, manufacturers, consultants and installation contractors.

In the past regular operation of the installation has followed a precursory check of the system to avoid any major errors and omissions; however, the comprehensiveness of this check has tended to rely on the quality of effort applied by one or two committed members of the team.

Excessive brightness patterns or undesirable glare may be due to a predominant use of lamps of too high a wattage; these will need to be changed. In security lighting systems, the brightness required for a successful deterrent effect may have been under-estimated and a change of Iuminaire or lamp type may be necessary to achieve the desired effect.

The designer has a responsibility for providing the commissioning brief, which should be comprehensive and define the responsibilities of the commissioning team. Failure to provide the team with an adequate brief can lead to abortive work through under-staffing, excessive commissioning costs and failure to execute a comprehensive check.

A commissioning brief will need to include the following items. 0 Schedules of equipment covering the items to be commissioned,

together with relevant plans and location identifications.

0 Copies of the specifications and tender documents.

0 Relevant codes applicable to commissioning and testing.

Relevant standards applicable to the system.

0 Manufacturers’ technical data sheets covering the equipment and its installation.

9 Wiring diagrams and supporting technical data advising the electrical contractor On matters such as the installation and setting-up of cable runs, ducts, trenching, switchgear, controls equipment and re- instatement.

Project information covering details of the basic concept through to the completed design. This may be better presented to the commissioning team as a ‘method statement’.

0 Designers’ operating and maintenance schedule.

7.2 Lamp depreciation Lamp replacement may be done individually when a lamp is seen to have failed (spot replacement) or all the lamps in an installation may be replaced periodically (group replacement). The former method generally applies to schemes with mixed light sources with varying lives: typically low level landscape lighting. The latter is frequently the cheaper option for road or area lighting because of the high labour costs of a multiplicity of spot replacements, and the inconvenience of lane closure on roads and because

72


7.3 Luminaire depreciation

the output of most lamps falls continuously with burning time, giving a low efficacy ahead of actual failure. The optimum time for bulk replacement can be determined from the lumen maintenance and mortality curves for the particular type of lamp, coupled with a knowledge of labour, lamp and electricity costs. Bulk replacement will be cheaper if it coincides with the periodic cleaning of the installation. I t is generally uncommercial to operate discharge lamps until they reach the point of electrical failure as by that time their light output will have deteriorated considerably, perhaps to as little as 50% of the light output at the end of the first 100 hours use. The most useful information, therefore, is the lumen maintenance and survival characteristics for any particular type of lamp from manufacturer’s data. With the aid of this information and considering the labour costs of lamp replacement a suitable replacement cycle can be worked out for any installation. In lighting calculations initial lumens should be used.

Light is lost by absorption as dirt accumulates on the inner and outer surfaces of a floodlight cover, on the reflector, and on the lamp. This dirt leads to the progressive deterioration of the reflector, especially if moisture is present.

The extent to which the optical performance of a floodlight, or other outdoor luminaire, is affected in service by dirt deposits depends on the climatic conditions, the degree of air pollution, the corrosion resistance of the optical surfaces, the location of the floodlight and the regularity with which the floodlight is cleaned.

In addition to the effect on optical performance, accumulation of dirt in the presence of moisture can lead to severe corrosion and consequent seizure of mechanical parts if the equipment is left unserviced for long periods.

Three things are necessary if the fall in light output from a system is to be kept within technically and economically acceptable limits. First, the equipment must be well-constructed; secondly, lamps must be changed and the luminaires cleaned regularly; thirdly, the maintenance factors used must be correctly related to the cleanness of the location, the cleaning characteristics of the luminaire and the cleaning cycle.

Good cleaning Poor cleaning choracteristics characteristics

Cleanness of location (e.g. sealed beam lamp, (e.9. large fittings,

very clean

Fairly clean

Fairly dirty

Very diriy

Cleaning (months)

3

6

9

12

15

18

21

cycle

Figure 7.1 Nomogram for determining the maintenance factor of an outdoor installation

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7.3.1 Maintenance factors For average conditions outdoors, a maintenance factor of 0.7 should be included in the design calculations, but if air pollution is heavy or regular maintenance is not possible a lower factor may be more appropriate to offset the greater light losses.

7.4 Economics

7.4.1 Cost comparisons

An approximate factor for use in floodlighting calculations can be derived from Figure 7.1 provided that the cleanness of the location, the cleaning cycle, and the cleaning characteristics (good or poor) of the lighting system are known. By joining a point on the left-hand scale, which indicates the cleanness of the location, to a point on the right-hand scale, which indicates the cleaning cycle, the maintenance factor can be read from the point where the line cuts the central scale, which is calibrated for both ‘good’ and ‘poor’ cleaning characteristics. The straight line illustrates the procedure.

Taking a fairly clean location and a cleaning period of 18 months, a maintenance factor of 0.7 is adequate for an installation with good cleaning characteristics, a factor of 0.6 is necessary if the characteristics are poor. The cleaning cycle needed to achieve a specified maintenance factor can be derived from the nomogram by drawing a line through the appropriate points on the left-hand and central scales and extending it to cut the right- hand (cleaning) scale.

Although not easily assessed in monetary terms, the benefits to the community of outdoor environmental lighting are very great and can be provided at much less cost than is commonly thought. Economy in all uses of electricity is essential, and environmental lighting schemes should be designed to utilise light as efficiently as possible and so avoid waste. When energy was cheap there was a tendency to achieve effects simply by using large quantities of light, now however, a more critical approach to design and choice of equipment is necessary.

The total cost of a lighting installation is the sum of the capital cost and the operating costs. Some, or all, of the following costs apply to most installations, and there are occasionally additional charges.

Capital costs may include:

0 design fees;

electrical installation;

initial lamps, luminaires, control gear, accessories;

0 columns or towers, fixings;

0 meter housings, equipment protection, time switches; and

0 electricity connection.

Operating costs may include:

0 electrical energy;

0 replacement lamps; routine maintenance, inspection, repairs, repainting;

supervisory, clerical, transport, plant and overhead charges;

0 way-leaves, rentals, insurance; and 0 removal, storage and re-erection of equipment (temporary and seasonal

installations).

It is convenient when comparing the economics of alternative lighting systems to assess all costs on an annual basis. Capiral costs may be expressed

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7.4.2 Tariff

7.4.3 Hiring

7.5 System management

as yearly costs based on the expected life of the installation and the amortisation charges of the principal. Most operating costs are incurred annually. Where components, e.g. some types of lamp, are replaced only once every two or three years, the appropriate proportion of their replacement costs can be allocated to the charges for the year. A simple comparison between the annual cost of different systems is obtained by adding the yearly amortisation charge to the operating cost. More refined costing methods may be justified for large projects.

In comparing alternative 1ampAantern combinations for floodlighting it is useful to evaluate as the common base, the total annual cost per thousand beam lumens, rather than repeatedly working out complete designs to satisfy illuminance and uniformity requirements, There are considerable differences in the periods of time during which different types of exterior installations are in use, typical hours of use being given in Table 7. I .

Table 7.1 Annual use of exterior lighting installations

Type of installation Number of Average hours Total hours days per of use of use per annum per day annum

Street lighring main street 365 11 4000 side street 365 6 2200

Indusrrial area floodlighting security lighting 365 11 4000

working areas 150 2 300

Decorative floodlighting,

prestige lighting 365 6 2200

conirnercial and niunicipal all the year round 365 6 summer only 200 6

2200 1200

Several types of electricity tariff are available and the regional electricity company should be consulted at the early stages of a project and the most advantageous tariff chosen. See Section 6.6.1

If an installation is likely to be operated for only a short time, it may cost less to hire equipment from a contractor or manufacturer than to buy it.

A person should be made responsible for the monitoring of the lighting system and effect a lighting maintenance scheme of regular cleaning and group lamp replacement if appropriate, as well as the servicing and checking of the switching system. Specialist maintenance contractors exist to provide the necessary technical and operational skills as well as having the necessary access equipment, which otherwise would be purchased by the user and perhaps left unused for the majority of its life.

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BS 6100: Part 3 Section 3.4: Building and civil engineering terms - lighting (London: British Standards Institution) (1985)

Lighting Guide: Sports (London: Chartered Institution of Building Services Engineers) (1990)

Technical Memoranda TM 12: Emergency Lighting (London: Chartered Institution of Building Services Engineers) ( I 986)

Lamp Guide (London: Lighting Industry Federation)

B S 4533: Luminaires (London: British Standards Institution)

Bibliography

CIBSE Publications (London: Chartered Institution of Building Scrvices Engineers)

Code for Inrerior Lighting ( I 984) Technical Memoranda T M 12: Emergency lighting (1986)

CIBSE Lighting Guides: Building and civil engineering sites (1975) Shipbuilding and ship repair (1979) Hosrile and hazardous environments (1983) l h e indusrrial environment (1989) Hospiral and heulth care buildings (1989) Sports (1990)

BSI Publications (London: British Standards Institution)

BS 4533 Electric luminaires BS S266 Code of Practice for emergency lighting BS 5489 Code of Praccice for road lighting CP I01 7 Disrribution of electriciry on construcrion and building sires

CIE Publications (Vienna: Commission Inrernationale dc I’Eclairage)

CIE 26 Internationul recommendutions for tunnel lifihring (1973) CIE 61 Tunnel entrance lighting (1984) CIE 26.2 Guide for rhe lighting of road runnels and underpasses (1988)

Government publications (London: HMSO)

Health and Safety at Work Act 1974 Seclions 2-4 und subsequent amendmenrs Health und Safety Guidance Note 38: Lighting at work The Offices Shops and Railway Premises Act I963 Electricity Supply Regulations 1937 and explanatory notes

Miscellaneous publications

Specifiers Design Manual (Eastern Electricity) ( I 988) Regulations for Electrical Installations - 15th Edirion (Institution of Electrical Engineers) Essentials of Security Lighting (Electricity Council) Lyons S L Exrerior Lighting for Industry and Security (Applied Science Publishers) (1980) Decorative Floodlighting Philips International Lighting Review 1979/4. Philips Internarional Lighting Review 1988/1 Residential Area Lighring - Requiremenrs and Recommendations Philips Enginecring Report No.43 Outdoor Lighting Handbook Thorn Lighting Limited (Gower Press)( 1974) Brighrness of Illuminated Advertisemenrs APLE Technical Rcport No.5 (Institute of Lighting Engineers)( 1973) Graham Underwood The Security of Buildings (Arch. Prcss)( 1984)

82

Glossary

absorption The loss of light during transmission through air, water or some other transparent or translucent medium.

accent lighting The highlighting of small individual features in the outdoor environment, e.g. a small statue set in a recess in a building facade.

adaptation The process which takes place as the eye adjusts to the brightness or the colour of the visual field.

asymmetric distribution A luminous intensity distribution which is not symmetric about the vertical axis through the luminaire.

azimuth angle An angle measured in the horizontal plane.

ballast Equipment used with discharge lamps for stabilising the discharge.

beam angle The total angle over which the luminous intensity of a beam drops to 50% of the peak value.

beam factor The percentage of the lamp flux in beam spread.

beam flux The total flux (lumens) within the beam spread.

beam spread The total angle over which the luminous intensity of a beam drops to 10% of the peak value.

candela The SI unit of luminous intensity, equal to one lumen per steradian (cd).

colour appearance A term used of a light source. Objectively the colour of a truly white surface illuminated by the source. Subjectively, the degree of warmth associated with the source colour. Lamps of low correlated colour temperature are usually described as having a warm colour appearance and lamps of high correlated colour temperature as having a cool appearance.

colour rendering A general expression for the colour appearance of objects when illuminated by light from a given source compared, consciously or unconsciously, with their appearance under light from some reference source. Good colour rendering implies similarity of appearance to that under an acceptable light source, such as daylight. The colour rendering properties of the lamp relate to this effect under specified conditions.

contrast A term which, when used subjectively, describes the difference in appearance of two parts of a visual field seen simultaneously or successively. The difference may be

Colour illustrations

The purpose of this section is to show the techniques described in the Guide. Each plate is referenced to a relevant section. The Institution is grateful to Derek Phillips Associates, Thorn Lighting, Philips Lighting, BEGA Lighting, British Railways Board and Norman Foster Associates for their help in compiling this section.

I

Plate 1. Yorkshire Building Society (3. I .I). The floodlighting is integrated with the buiiding form to express the strong modelling of the upper storeys. The luminous background signs are well positioned and effective showing good use of colour and tonal contrast.

Plate 2. Hanley shopping centre (3. I .3). Anappropriatc human scale is created in this shopping centre by rhe choice of luminaires and lamp posts, whilst general lighting is provided unobtrusively by wall mounted floodlights.

Plate 3. Chateau de Castries (3. I .7). Carcfully positioncd floodlighting brings out rhc modclling of rhc building and rhc arcade. 'The drama of silhoucttc is uscd in crcating a scnsc of' enclosure.

ip

Plate 4. Manchesrer University Quad (3.1.8). Lighting plays its part in crearing interest in thc sequential movement from one spacc to the nexr. The degrcc of cmphasis in each part of thc schcnie is well controlled. The scale and character of the wall lanterns is related to that of rhc archway.

w

Plate 5. Warergatc (5.1.10). Dramatic h u t resrrained iisc of diffcrcnt colour sources on an architcctural monument on the edgc of a am;ill city park.

Plates 6 & 7. Bartlctr shopping model (4. I ) . Model studies and appraisals of shopping precincts show an overall coverage of light together with window display lighting and acccnt lighting on trees, sculpture or seating areas to provide a feeling of safety and sccurity as wcll as creating a pleasant ambience. The diffcrcncc which a degree of overall lighring can make is clearly illustrated.

Plate 8. Multi-screen cincma Walsall(4.4.1). The principal circulation route of the car park is well defined by the rhythmic spacing of the posts and the more uniform distribution at road level. Clusters of small luminaires and the vicw of thc lit interior draw attention to the entrance co thc building.

Plate 9. St. Pancras station (4.6). T h c platform\ are well illuminated, the edges arc clearly defincd by wehitc liiics. .fhc roof i 5 lit indircctly by rcflcction from the light colourcd platforms in conjunction wilh thc light finish on the roof' structure.

Plate 10. Open tree and flowerbeds (4.16.1). Localised highlighting is used in the flower- bed, the ‘open’ type of tree is floodlit from below.

Piate 11. Solid tree (4.16.2). Frontal lighting is used for tall poplar trces and for those with dense foliage.

Plate 12: Opcn trees (4.16.2). Upward lighting from floodlights in the ground near to the tree trunks reveals rhe tracery of thc branches of deciduous trees in winter.

8

Plate 13. Tower Bridge (4.17.2). Tower Bridge combines both solid masonry and open lattice work. The solidity of the towers is emnhasised by illuminating the river faces more brightly than those facing the shores, whilst lighting at grazing angles is used to show up the latticc work. The principal light source is metal halide with fluorescent sources incorporated into the linear overhead walkways; high pressure sodium is used to floodlight the insignia.

Plate 14. Towcr Bridgc aiming arrows (4.17.2). The location and aiming directions of somc of the metal halide floodlights are superirnposcd on this photograph of Towcr I3ridgc.

Plate 15. Sculpture in quad (4.18). Sculpture modclled by floodlighting from lantern mounted at eaves level on a facing building with light directed obliquely to bring out form and texture.

Plate 16. Brindavoii (iarden Mysorc India (4.22). Vertical jcts illuminated by narrow symmetrical beam submersible Iloodlights.

Plate 17. Fort George (5.3). Effcctivc floodlighting by limited means. ’l’hc posirion of the floodlights ensure good modelling of thc facetted gable end and ofthe projcctmg wings at the rear. The parapets arc defined and thc triangular shadow on the gable matches the roof pitch.

Plate 18. McArthy and Stow (5.3.1). Thc light colourcd framework responds to rhc floodlighting. Variety i s created as the dark intcrrnediate pancls eirlier contrast with the lit interior forming a grid pattern or combine with unlit windows to give a vertical emphasis.

Plate 19. Stockley Park, Hasbro restaurant (5.3.2). Intcrior lighting and thc cxtcrnal appearance by night have to be considered jointly in buildings with a large proportion of glazing. A restaurant conceived as a glass lantern is effectively contrasted with the solidity of adjaccnt buildings.

Plate 20. Trcntham Gardens (5.7). Landscapc lighting wirh the use of silhouetted forms against a floodlit building to give depth and distancc to thc view in a pleasure park.

Plate 21. Stanstead Airport (5.3.3). An uplighting technique is used for the concourse. The floodlights, cmcrgcncp lighting and elecrrical eyuipmcnt arc part of8 service and inforination pod at thr base of' each structural unit.







Bibliography












82

Glossary
















brightness or colour or both. Objectively, the term expresses numerically the luminance difference by various formulae.

correlated colour temperature The temperature of a full radiator that emits radiation having a chromaticity (colour quantity defined by an accepted system) nearest to that of the light source being considered. The unit is the Kelvin, K. As an example, the colour of a full radiator at 3500 K is the nearest match to that of a white fluorescent lamp, which is therefore said to have a correlated colour temperature of 3500 K.

cut-off angle A term applied to a luminaire. The angle measured from the downward vertical upwards to the first line of sight at which the lamp(s) or surface of high brightness is no longer visible. For a floodlight, this angle is usually measured from the beam axis.

diffused lighting Lighting in which the flux comes from many directions, none of which predominates.

direct lighting Lighting in which the greater part of the flux reaches a surface directly, i.e. without reflection from other surfaces.

dimming The control of the light output from the light source by the electrical or resistive methods.

directional lighting Lighting designed to illuminate an object or surface predominantly from some preferred direction.

disability glare Glare which impairs the ability to see detail.

discharge lamp See lamps.

discomfort glare Glare which causes visual discomfort.

emergency lighting Lighting provided for use when the main lighting installation fails.

escape lighting Emergency lighting provided to ensure that the means of escape can be safely and effectively used at all material times.

extra-low voltage Normally not exceeding 50 V AC or 110 v DC whether between conductors or to earth.

flicker A visible oscillation in luminous flux.

flux See luminous flux.

floodlight See luminaire.

footpath A means of passage for pedestrians.

general lighting Lighting designed to illuminate the whole of an area uniformly, without provision for special local requirements.

glare The discomfort or impairment of vision experienced when parts of the visual field are excessively bright in relation to the general surroundings.

hazardous environment An environment in which a risk of fire or explosion exists.

high pressure discharge lamp See lamps.

ingress-protection (IP) number A two-digit number associated with a Iuminaire. The first digit classifies the degree of protection the luminaire provides against the ingress of solid foreign bodies, the second digit classifies the degree of protection the luminaire provides against the ingress of moisture. Details of the nature of the protection achieved at different levels is given in BS 4533'9'.

illuminance The luminous flux incident on unit area of a surface. The unit is the lux which is one lumen per square metre.

illumination The process of lighting an object or surface.

incandescent lamp See lamps.

indirect lighting Lighting in which the greater part of the flux reaches a surface only after reflection at other surfaces and particularly at the roof or ceiling.

intensity See luminous intensity.

isolux curve A line joining points of equal illuminance on a surface (also equilux curve).

lamps There are many different types of lamp. - Discharge lamp. A lamp in which the light is produced

either directIy or by the excitation of phosphors by an electrical discharge through a metal vapour (e.g. mercury, sodium), gas (e.g. xenon), or a mixture of several gases and vapours.

- Incandescent lamp. A lamp in which light is produced by a filament heated to incandescence by the passage of an electric current through it. The filament is enclosed in a glass bulb which is either evacuated or, more usually, filled with an inert gas at low pressure. A tungsten filament is used in most incandescent lamps which are consequently known as tungsten lamps.

light loss factor The ratio of the illuminance provided by the installation at some stated time, with respect to the initial illuminance, i.e. that after 100 hours of operation. The light loss factor is the product of the lamp lumen maintenance factor, the luminaire maintenance factor and the room surface maintenance factor.

83


lighting design lumens Lamps vary in flux output, both between themselves and through their operating lives. The lighting design lumen is a nominal value which is representative of the average light output of each type or size of lamp throughout its life.

local lighting Lighting designed to illuminate a particular small area.

louvre An open grid of translucent or opaque elements attached to the base of a luminaire in such a position that lamps cannot be seen directly above a given angle, e.g. 60° to the downward vertical.

lumen The S I unit of luminous flux, used in describing a quantity of light emitted by a source or received by a surface. A small source which has a uniform luminous intensity of one candela emits a total of 47r lumens in all directions and emits one lumen within unit solid angle.

luminance The physical measure of the stimulus which produces the sensation of brightness measured by the luminous intensity of the light emitted or reflected in a given direction from a surface element, divided by the area of the element in the same direction. The SI unit of luminance is the candela per square metre, the relationship between luminance and illuminance is given by the equation

illuminance x reflectance Luminance =

n- This equation applies to a matt surface. For a non matt surface, the reflectance is replaced by the luminance factor.

luminaire An apparatus which controls the distribution of light given by a lamp or lamps and which includes all the components necessary for fxing and protecting the lamps and for connecting them to the supply circuit. Luminaire has superseded the term lighting fitting.

luminous efficacy The ratio of the luminous flux emitted by a lamp to the electrical power consumed by it. When the power consumed by control gear is taken into account this term is sometimes known as lamp circuit luminous efficacy and is expressed in lumens/circuit watt.

luminous flux The light emitted by a source or received by a surface. The quantity is derived from radiant flux by evaluating the radiation in accordance with the spectral sensitivity of the standard eye as described by the CIE Standard Photometric Observer.

luminous intensity A quantity. which describes the power of a source or illuminated surface to emit light in a given direction. It is the luminous flux emitted in a very narrow cone containing the given direction divided by the solid of the cone: The result is expressed. in candelas.

luminous intensity distribution The distribution of the luminous intensity of a lamp or luminaire in all spatial directions. Luminous intensity

distributions are usually shown in the form of a polar diagram or a table for a single vertical plane, in terms of candelas per 1000 lumens of lamp luminous flux.

lux The SI unit of illuminance, equal to one lumen per square metre.

maintenance factor The ratio of the illuminance provided by an installation in the average condition of dirtiness expected in service, to the illuminance from the same installation when clean. The maintenance factor is always less than unity.

maintained illuminance The average illuminance over the reference surface at the time maintenance has to be carried out by replacing lamps and/or cleaning the equipment and room surfaces (if applicable).

minimum illuminance The lowest illuminance occurring at any point and at any time on the working plane in the working area.

mounting height Usually the vertical distance between a luminairellantern and the working plane, but sometimes the distance between the luminaire and the floor.

reflectance The ratio of the luminous flux reflected from a surface to the luminous flux incident on it. Except for matt surfaces, reflectance depends on how the surface is illuminated but especially on the direction of the incident light and its spectral distribution. The value is expressed as either a decimal or as a percentage.

ref lector A device for controlling the flux from a lamp by reflection at suitably shaped surfaces. These may be either specular (e.g. mirrored glass or polished aluminium) or diffuse (e.g. dimpled aluminium or vitreous enamel ). In the former, the light is reflected in accordance with the laws of the optical reflection. In the latter the light is diffused, largely without reference to any particular direction.

reflector lamp An incandescent or discharge lamp in which part of the bulb, suitably shaped, is coated internally with a reflecting material which partly controls the distribution of luminous intensity emitted from the lamp. Incandescent lamps have a metallic reflecting material which gives a beam; discharge lamps have a white or fluorescent reflecting material which gives diffused light. Also, a fluorescent tubular lamp in which one side of the tube is coated with a white reflecting material so that most of the light is emitted from the other side.

standby lighting Emergency lighting provided to enable normal activities to continue.

symmetric distribution A luminous intensity distribution which is symmetrical about the vertical axis through the luminaire.

transmittance The ratio of luminous flux transmitted by a material to the incident luminous flux.

84


tungsten halogen lamp A tungsten filament lamp containing halogens. It does not require any control gear but may require low voltages. It achieves full light output immediately. The bulb may be sensitive to operating position, small voltage variations and vibration. The envelope surface is liable to deteriorate if touched with bare hands.

uniformity ratio The ratio of the minimum illuminance to the average illuminance. In some instances, the ratio of the minimum to the maximum illuminance is quoted. The ratio usually applies to values on the working plane over the working area.

utilisation factor The total flux reaching a given plane, such as a building facade, divided by the total lamp flux.

visual environment The environment either outdoors or indoors as seen by the observer.

visual field The full extent of what can be seen when looking in a given direction.

waste light factor The proportion of light produced by an exterior area floodlighting installation that falls on the area to be lit (typically 0.8).

zonal flux diagram A diagram displaying the light flux emitted by a floodlight into angular zones.

85


- Performance: activity related areas where lighting needs are known. e.g. sports events, work places, roads, stations, airports, ports, etc.

- Character: ambience, image, mood.

- maintenance provisions, e.g. hard standing for tower

- switching arrangements, cable and protective device

- location of control or supply equipment.

access;

sensing; and

A2.3 Design A2.4. Design appraisal

The basis of all design is human need, perception and response. A successful design must satisfy the practical requirements of safety and security, and at the same time satisfy both psychological and aesthetic needs.

The eye adjusts to the ambient light and can be extremely sensitive to very weak sources where only the minimum of visual information is required. The lighting design is often required to function at various incremental levels.

- Minimum lighting for safety at times of least use.

- General lighting for normal uses.

- Special lighting for visual effects.

A2.3.1 Technical solutions

It is advisable to seek professional guidance at an early stage. The best schemes are the direct result of a close partnership between the electrical engineer and the environmental designer. The skill of the lightingengineer lies in the practical realisation of the design objectives using the most appropriate technical resources.

A2.3.2 Basic decisions

There is no absolute single solution to any given situation. There is a basic design correlation however between:

(a) locations of light sources i.e. mounting height, spacing, distance from lit objects etc.; and

(b) types of light sources i.e. intensity, distribution, colour, etc.

Most design processes begin with a trial proposal which presupposes elements of both (a) and (b) based on experience. These proposals are modified in view of other considerations such as:

- colour of light and colour rendering;

- efficiency and costs;

- visibility of light sources (concealed, visible, seen directly).

A2.3.3 Technical design

The proposals are normally made on a site plan augmented by sections and elevations where necessary. These must show: - location of each lighting source;

- a specification of the type of light source;

- the means of supporting the luminaires;

A skilled designer can interpret a technical drawing and be able to ‘see’ from it the visual effect. Lay clients, however, may need help. This can be done in a number of ways.

Demonstrations can be provided. Fittings can be rigged temporarily. Samples provided. Similar installations visited.

Drawings can be highlighted. Plans can be coloured to illustrate the distribution of light on a given horizontal plane.

Illustrations can be drawn. Elevations and perspective sketches can convey an impression of the visual effect.

Models can be made. These can be used to demonstrate principles. Light sources must however be reduced in power and relate to the scale.

A 2 5 Parameters for choice

The main design objectives can always be met by a wide variety of equipment. The following considerations also determine the optimum solutions:

- capital cost of initial installation;

- running costs;

- maintenance costs;

- resistance to anticipated abuse;

- colour rendering; - day-time appearance;

- appropriateness/acceptability;

- appreciation of improved environment;

- increased utilisation of the landscape;

- increased sense of security; and

- increased sense of civic pride.

References

1 BS 5266: Code of practice for emergency lighting (London: British Standards Institution)

2 Lighring Guide: The industrial environment (London: Chartcred Institution of Building Services Engineers) (1 989)

Lighting Guider Building and civil engineering sites (London: Chartered Institution of Building Services Engineers) (1975)

B S 5489: Code of pracrzce for road lighiing (London: British Standards Institution)

3

4

81







Bibliography












82

Glossary
















Appendix 1 Floodlighting design and calculation methods

This appendix describes a simple procedure for designing floodlighting schemes for buildings and open spaces, and gives methods of calculations applicable to floodlighting, lighting of outdoor areas bv column-mounted lanterns and

Table Al . l Building floodlighting: suggested illuminance for use in preliminary design

Illuminance (lux)

liihtini of individual featires. Careful design will prevent Approximate Typical reflectance materials’ condition Low Medium High

District brightnessz Surface overlighting and waste of light and electricity.

Clean 15 25 40 Fairly clean 20 35 60 Fairly dirty 45 75 120

0.6 Portland stone Clean 20 35 60 floodlighting schemes Fairly clean 35 55 90

Fairly dirty 65 110 180

0.8 White brick

A1 . I Design procedures for

~

0.4 Middle stone, Clean 30 50 80 medium concrete Fairly clean 45 75 120

Fairly dirty 90 150 240

The design of many decorative floodlighting schemes rely for success on a combination of aesthetic appreciation, experience, intuition, and flair. The followina simdified method of floodlighting design is based on two’ assumptions. 0.3 Dark stone Clean 40 60 100

Fairly clean 55 90 150 - First, that designers have under their control the Fairly dirty 110 180 300

following: the floodlight type (i.e. type of intensity distribution); the lamp type and wattage (i.e. lumen 0.2 Granite, Clean 55 90 150

red brick Fairly clean 80 140 230 Fairlydirty 160 280 450 output); and the location of the floodlights, and their

aiming.

-

I Based on reflectance for a white light. Values may differ if low pressure sodium or high pressure mercury lamps, or lamps emitting light of a predominant colour are used; illuminance should then be decided by site

- Secondy that a uniform is required over the lit area.

trials. 2 Typicaldistricts are: low brightness-rural; medium brightness- suburban; high brightness-town and city centres.

Although these assumptions are unlikely to be wholly justified in practice, the procedure described below will give reasonably satisfactory results for straightforward schemes. The design of large and complicated schemes usually calls for specialised knowledge and a qualified lighting engineer should be consulted. Al.1.2 Type of lamp and floodlight

The simplified procedure comprises of 5 steps: Based on the lighting requirements of the project and using - - - determination of required illuminance;

choice of lamps and floodlights best suited to the projects;

calculation of the number and wattage of floodlights needed to give the required illuminance;

and specification of aiming directions for the floodlights.

Table Al. 1 for guidance, the most suitable-type of lamp can be selected; the wattage of lamp can be decided later.

The most suitable floodlight (i.e. symmetrical, asymmetrical and double asymmetrical beams) for a particular application will depend on the site geometry, e.g. the height and lengthof

beam floodlights are frequently used for long-range building floodlighting and similar applications. Asymmetric and double asymmetric beam floodlights principally for such purposes as lighting open spaces from around the perimeter and for close-offset floodlighting of buildings.

determination O f best mounting positions for floodlights; a building relative to the floodlight locations. Symmetrical

u v Y

Al. l . l Required illuminance

The illuminance requirements for open spaces such as outdoor shopping precincts and parks are given in Section 4. Precise requirements for the illuminance of buildings cannot be given because the values are affected by many variables. However, the general recommendations of Table Al. 1 are a useful starting point for design provided that the reflectance of the building material, its state of cleanliness and the district brightness are known or can be determined; it is assumed that the building surface is reasonably matt. Successful building floodlighting depends on much more than achieving the recommended illuminance and there is only an indirect relationship between illuminance, luminance and the visual effect produced.

76

Al.1.3 Number and wattage of floodlights

The utilisation of light from the lamp varies with the light output ratio (efficiency) of the floodlight, its light distribution, and the lighting layout. Most manufacturers supply photometric data that enable the user to make a close estimate of a floodlight’s performance in a given situation.

The total lamp flux needed ro provide a given illuminance over a given area is derived from the formula:

A E MF UF

* = -


where:

= total lamp flux (lm) A = area (my) E = maintained illuminance (Ix) MF = maintenance factor U F = utihsation factor

The flux required also depends, to a small extent, on the effects of inter-reflection and atmospheric absorption, but these can be ignored in practical designs for the installations dealt with in this Guide.

The appropriate maintenance factor may be derived from Table 7.1; if the necessary information is not available, a factor of 0.7 should be used. The utilisation factor is the product of the light output ratio of the floodlight (available from the manufacturer, normally known as the beam factor) and the useful light factor of the installation. This last factor is the fraction of the flux emitted by the floodlights which falls on the surface being lit, this is known as the waste light factor. Experience indicates that on average the utilisation factor will be in the range 0.25-0.35; it is often sufficiently accurate for initial design purposes to take a value of 0.3.

Nominal values of lamp flux (the initial lumens) are given in manufacturers' catalogues, and the number of lamps needed to provide the total flux can thus be obtained by dividing the total flux by the flux from one lamp. The total flux can often be provided in different ways, e.g. by using either a few lamps of high wattage (i.e. high light output) or more lamps of lower wattage. The choice is best made after the preferred floodlight locations have been finalised.

Al.1.4 Determination of floodlight locations

General factors influencing the choice of floodlight locations for building floodlighting are discussed in Section 5.3. The following comments are more specific and apply to close- offset floodlighting schemes for buildings, and the perimeter schemes for open spaces.

A 1.1.4. 7

When deciding the most suitable locations for asymmetric and double asymmetric beam floodlights used in a close- offset scheme for a building, account should be taken of the generally accepted height/offset ratios shown in Table Al.2.

Close-offset building floodlighting

Table A1.2 Approximate heightloffset ratios ~ _ _ _ _ _ _ _ _ _ _ _ _

Beam spread Typical class Height/offset ratio ~

Wide H5O V5" 2: 1 Medium H5" V3O 4: I Narrow H5O V l 0 greater than 4: 1

Narrow-spread floodlights used in close-offset systems become increasingly less effective as the heightloffset ratio increases beyond 10: 1 because the illuminance on the building face falls off rapidly with height; a second row of floodlights may be needed to maintain acceptable uniformity

Elevation

Figure Al . l Height h, and perpendicular offset distance d.

over the facade. There is no precisely defined maximum offset distance beyond which close-offset systems should not be used; the deciding factor is the site geometry. However, it is recommended that these qualifying factors should be carefully considered if it is proposed to use asymmetric and double asymmetric beam floodlights at an offset distance of more than 8 m. At offset distances greater than 8 m, long- range systems are usually more appropriate. In some circumstances a combination of symmetric, asymmetric and double asymmetric beam floodlights may give the best result.

A 1.1.4.2 Perimeter floodlighting

The floodlights used for lighting an outdoor area from points around the perimeter should be spaced apart at a distance of 1:4 times the mounting height. The most suitable combination of mounting height and number of lighting points necessary to maintain satisfactory spacing and to accommodate the number of floodlights needed to give the specified illuminance and uniformity should be assessed.

This may suggest that the number of points indicated by the initial calculation could, with advantage, be altered. Care must be taken not to reduce the number too far because the uniformity requirements may then demand the use of columns whose height is such that their cost is excessive and their appearance out of scale with the surroundings. Conversely if too many lighting points are used, the cost of the coIumns, floodlights, lamps and cabling may also be excessive, and in some areas the number of columns may inconvenience pedestrians. A fairly common problem with perimeter lighting is the difficulty of obtaining acceptable uniform illuminance along the perimeter line. It is difficult to avoid dark patches between the lighting points, even with widespread floodlights, if columns are sited on the line. Where possible, therefore, the columns should be set back from the perimeter. It is usually wise to avoid arrangements that call for critical aiming of the floodlights. Schemes should be designed to provide adequate overlap of the beams from individual floodlights and the use of a simple aiming pattern. Graphical methods are normally used for designing the overlap pattern of illuminance, and hence the aiming pattern for the floodlights. A record should be kept, and the floodlights marked or pinned so that the correct alignment is maintained.

77


floodlight projectors so it is common practice to use an estimated utilisation factor of 0.3 in the first stages of calculation. This figure is low for asymmetric and some symmetric projectors giving precise light control and too high for wide angled projectors which will project light beyond the boundaries of the area being considered. As a first

L

Horizontal approximation however it will allow the designer to establish

Al.2 Methods of calculation Al.2.2 Inverse square law and cosine law

P

Al.2.1 The lumen method The inverse square law and cosine law can be used to calculate illuminance at a point from intensity data.

The lumen method is the best known of the flux design methods and has the great virtue of simplicity. With experience it can be used with some degree of precision. The basic formula is usually expressed as follows:

A E N =

L BF WLF MF

N L BF WLF MF

A E =

Where:

(b) Plan

N = number of luminaires A = area to be lighted (m*) E = illuminance required (lx) MF = maintenance factor L = lamp output per luminaire (lm) BF = beam factor (proportion of lamp lumens

contained within the beam) WLF = waste light factor (proportion of light

falling on area to be lit, normally assumed to be 0.9 but in difficult situations it may reduce to 0.5 of lower)

or Figure A1.2 Conventions used in calculation of illuminance at point p from a source at s.

If an estimated utilisation factor has been used it may be necessary to check the results of this calculation by using other design methods.

A 1.2.1.1 Atmospheric losses

where:

CY

8

d

EP h

I

angle of a vertical plane to the source, equal to zero for a plane normal to the source angle of incidence at point p for horizontal plane illuminance the straight line distance between the source and point p horizontal illuminance at point p (lx) illuminance at point p normal to source (1x) vertical illuminance at point p (lx) the vertical height from the plane of point p to the source intensity in the direction of point p (cd)

Horizontal plane illuminance.

or An important factor which can affect the final illuminance value in an outdoor installation is the atmospheric loss caused

day and the season as well as location, and should be taken into account when specifying design values of illuminance.

The losses also depend upon the mounting-height and the length of ‘throw’. Although it is impossible to give precise guidance on this point, typical losses on a clear night for a four-tower installation with 30-45 m towers are 20-30%. Calculations should be based on performance on a clear night, as the effects of other weather conditions are too variable to be taken into account. For example, light drizzle

I can change the distribution of illuminance without significantly

a near black-out. d2

I case - dz

by airborne smoke, fog, etc. This will vary with the time of E p h -

Illuminance on a Plane normal to the source.

- I CoSw - h2 E*,

or

- - - reducing the average value, on the other hand smog can cause EPfl

78


Vertical plane illuminance (facing the source).

- I COSV tane hZ

E p v -

or

Vertical plane illuminance at an angle to the source.

or

A 1.2.3.1 Example of use of the zonal flux diagram

An area measuring 20 rn x 20 m is to be lit using a single floodlight mounted on an 8 m high column, see Figure Al.4. (Floodlight type and lamp wattage having been found using the initial assumption that utilisation factor is 0.3).

Peak intensity for the floodlight is aimed at a distance 11.9 m along line EF, normal floodlight aiming would be about two thirds of distance along the centre line. The angles of interest are W (25O), X @lo), Y (56O), and Z (12'). The points A,B,C,D can then be plotted onto the zonal flux diagram, and joined together to map out an area. The co-ordinates for the points are: A(-W,+Z); B(-X,-Y); C(+X,-Y); and D(+X,+Z).

I cos28 sin8 COW

h*

Note that the maintenance factors and absorption factors must be included in the point-by-point calculations.

- Ep -

Al.2.3 Zonal flux diagrams

The zonal flux diagram is very adaptable as it allows any aiming angle in elevation to be investigated at any mounting height without conversion factors. A typical diagram is shown in Figure A1.3. This is divided through the plane of symmetry for the luminaire, with isocandela lines plotted on the angular grid on the left hand side, and figures indicating the total flux in each angular zone on the right. Flux totals i.e. 344 in Figure A1.3, refer only to half diagram so values should be multiplied by 2. The diagram can be used to give either point values of illuminance or the total flux intercepted by the area to be lit.

Figure A1.4 Floodlight geometry.

Angle from beam axis in degrees horizontal

Figure A1.3 Typical zonal flux diagram and associated intensity distribution diagram. Note: All data on the zonal flux diagram is based on 1000 lamp lumens so that the values shown on the diagram must be multiplied by the lamp flux in kilo lumcns for each lamp type. In this case, the floodlight sclected takes a 150 W SON-T lamp, which gives 16000 lumens (100 hour value) so all values on the zonal flux diagram must be multiplied in this instance by 16.

A

This information should be plotted on the zonal flux diagram as shown in Figure A1.5.

If part of the area to be lit falls outside the lowest isocandela contour, then more than one floodlight would be necessary or a wider beam floodlight should be used. An increased mounting height could also be considered.

The lumen values (numbers) inside each box should be added up and as the area to be lit is symmetrical, the value should then be doubled, see Figure A1.5. If the line cuts only part of a box, the zonal lumen value within the lines is estimated. So the utilisation factor is equal to twice 222 divided by 1000, that is 0.44.

The average horizontal illuminance will be equal to the utilisation factor multiplied by the lumen output of the lamp, divided the area to be lit:

(0.44 X 16000)/(20 x 20) = 18 lux.

If the elevation angle of the floodlight is changed, the outline of the area superimposed on the zonal flux diagram can be moved up and down the vertical axis (tilting the floodlight up is represented by moving the outline down).

79



Figure A1.5 Annotated zonal flux diagram.

Appendix 2 Landscape method

design

A guide to the basic stages in the development of an outdoor lighting scheme. In considering the development in the context of landscape design it is important to understand the design process involved. This may be summarise in the following stages: survey; analysis; design; and appraisal.

A2.1 Survey

It is important to know and understand the site. Existing sites should be surveyed and where sites are being developed copies of the project drawings obtained. Useful scales are 1:500 for site plans and 1:200 for details.

A2.1.1 Plans

Roads: classification, alignment, width, crossings, laybys, bollards, signs, parking.

Paths: alignment, width, steps, ramps, signs. Use e.g. by pedestrian, cyclist.

Buildings: use, shape and location, entrances, services.

Artefacts: phone kiosks, post boxes, seats, signs. Art objects.

Natural: tree species, location, shrub species, hedge species, pools, water channels.

3+3+2= a 22+20+ 13 = 53

24+22+ 18 = 67

13+ 12+10+4 = 39

6+6+5+4 = 21

4+4+4+3+1 = 16

4+3+3+2+ 1 = 13

2+1+1+1 = 5

222 -

A2.1.2 Elevation/sections

Vertical features, in reflecting light provide the principal clues in order to identify places.

Buildings: form, texture, colour, night-time uselappear- ance. Treedshrubs: species, height, form, density of foliage, colour .

A2.1.3 Functional requirements

The need for lighting arises from human activities. It is necessary to survey the standards which are recommended or laid down for the proposed site uses. For example: Ministry of Transport classification (transport); Sports Council (sport); Factory Inspectorate (places of work); police and insurance companies (security).

A2.2 Analysis

The purpose of this stage is to produce a performance brief. This provides basic criteria against which the success of the design can be measured.

The most direct technique is to write on a survey drawing of the site all the factors which must be considered indicating the relevant features. The major factors to be considered follow.

- Site conditions: obstacles; changes of level; security of people; key elements and principal views; movement patterns and routes; destinations; etc.



Figure A1.5 Annotated zonal flux diagram.

Appendix 2 Landscape method

design

A guide to the basic stages in the development of an outdoor lighting scheme. In considering the development in the context of landscape design it is important to understand the design process involved. This may be summarise in the following stages: survey; analysis; design; and appraisal.

A2.1 Survey

It is important to know and understand the site. Existing sites should be surveyed and where sites are being developed copies of the project drawings obtained. Useful scales are 1:500 for site plans and 1:200 for details.

A2.1.1 Plans

Roads: classification, alignment, width, crossings, laybys, bollards, signs, parking.

Paths: alignment, width, steps, ramps, signs. Use e.g. by pedestrian, cyclist.

Buildings: use, shape and location, entrances, services.

Artefacts: phone kiosks, post boxes, seats, signs. Art objects.

Natural: tree species, location, shrub species, hedge species, pools, water channels.

3+3+2= a 22+20+ 13 = 53

24+22+ 18 = 67

13+ 12+10+4 = 39

6+6+5+4 = 21

4+4+4+3+1 = 16

4+3+3+2+ 1 = 13

2+1+1+1 = 5

222 -

A2.1.2 Elevation/sections

Vertical features, in reflecting light provide the principal clues in order to identify places.

Buildings: form, texture, colour, night-time uselappear- ance. Treedshrubs: species, height, form, density of foliage, colour .

A2.1.3 Functional requirements

The need for lighting arises from human activities. It is necessary to survey the standards which are recommended or laid down for the proposed site uses. For example: Ministry of Transport classification (transport); Sports Council (sport); Factory Inspectorate (places of work); police and insurance companies (security).

A2.2 Analysis

The purpose of this stage is to produce a performance brief. This provides basic criteria against which the success of the design can be measured.

The most direct technique is to write on a survey drawing of the site all the factors which must be considered indicating the relevant features. The major factors to be considered follow.

- Site conditions: obstacles; changes of level; security of people; key elements and principal views; movement patterns and routes; destinations; etc.


- Performance: activity related areas where lighting needs are known. e.g. sports events, work places, roads, stations, airports, ports, etc.

- Character: ambience, image, mood.

- maintenance provisions, e.g. hard standing for tower

- switching arrangements, cable and protective device

- location of control or supply equipment.

access;

sensing; and

A2.3 Design A2.4. Design appraisal

The basis of all design is human need, perception and response. A successful design must satisfy the practical requirements of safety and security, and at the same time satisfy both psychological and aesthetic needs.

The eye adjusts to the ambient light and can be extremely sensitive to very weak sources where only the minimum of visual information is required. The lighting design is often required to function at various incremental levels.

- Minimum lighting for safety at times of least use.

- General lighting for normal uses.

- Special lighting for visual effects.

A2.3.1 Technical solutions

It is advisable to seek professional guidance at an early stage. The best schemes are the direct result of a close partnership between the electrical engineer and the environmental designer. The skill of the lightingengineer lies in the practical realisation of the design objectives using the most appropriate technical resources.

A2.3.2 Basic decisions

There is no absolute single solution to any given situation. There is a basic design correlation however between:

(a) locations of light sources i.e. mounting height, spacing, distance from lit objects etc.; and

(b) types of light sources i.e. intensity, distribution, colour, etc.

Most design processes begin with a trial proposal which presupposes elements of both (a) and (b) based on experience. These proposals are modified in view of other considerations such as:

- colour of light and colour rendering;

- efficiency and costs;

- visibility of light sources (concealed, visible, seen directly).

A2.3.3 Technical design

The proposals are normally made on a site plan augmented by sections and elevations where necessary. These must show: - location of each lighting source;

- a specification of the type of light source;

- the means of supporting the luminaires;

A skilled designer can interpret a technical drawing and be able to ‘see’ from it the visual effect. Lay clients, however, may need help. This can be done in a number of ways.

Demonstrations can be provided. Fittings can be rigged temporarily. Samples provided. Similar installations visited.

Drawings can be highlighted. Plans can be coloured to illustrate the distribution of light on a given horizontal plane.

Illustrations can be drawn. Elevations and perspective sketches can convey an impression of the visual effect.

Models can be made. These can be used to demonstrate principles. Light sources must however be reduced in power and relate to the scale.

A 2 5 Parameters for choice

The main design objectives can always be met by a wide variety of equipment. The following considerations also determine the optimum solutions:

- capital cost of initial installation;

- running costs;

- maintenance costs;

- resistance to anticipated abuse;

- colour rendering; - day-time appearance;

- appropriateness/acceptability;

- appreciation of improved environment;

- increased utilisation of the landscape;

- increased sense of security; and

- increased sense of civic pride.

References

1 BS 5266: Code of practice for emergency lighting (London: British Standards Institution)

2 Lighring Guide: The industrial environment (London: Chartcred Institution of Building Services Engineers) (1 989)

Lighting Guider Building and civil engineering sites (London: Chartered Institution of Building Services Engineers) (1975)

B S 5489: Code of pracrzce for road lighiing (London: British Standards Institution)

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This page has been reformatted by Knovel to provide easier navigation.

INDEX

Index Terms Links

A

Absorption 82

Accent lighting 82

Access routes 14

Adaptation 82

Aesthetic considerations 3

Amenity 12 41

Arcades 8

Asymmetric distribution 82

Atmospheric losses 78

Auditoria 36

Auto bank points 16

Azimuth angle 82

B

Ballast 65 82

Bandstands 36

Banks 16

Beam angle 82

Beam factor 82

Beam flux 82

Beam spread 82

Bicycle racks 16

Bollards 17

Bridges 27

Brightness 6

Building societies 16

Buildings 43

Bushes 25

Business parks 9

C

Cable colour 69

Calculation 78

Candela 82

Car parks 10

Index Terms Links


Castle ruins 30

Central power system 52

Chemical works 27

Church halls 17

Circulation areas 8

Clocks 31

Coach 14

Cohesion 3

Colleges 54

Colour 4 48

Colour appearance 4 82

Colour rendering 82

Columns 65

Commercial plant 27

Commercial zones 9

Commissioning 72

Community buildings 17

Concerts 36

Concourse 14

Contrast 82

Control 66

Control gear 65

Correlated 4

Correlated colour temperature 83

Cosine law 78

Covered precincts 8

Crime 53

Cut-off angle 83

D

Deterrent 54

Diffused lighting 83

Dimming 83

Direct lighting 83

Directional lighting 83

Disability glare 83

Discharge lamp 83

Discomfort glare 83

District brightness 6

Domes 50

Index Terms Links


E

Economics 74

Educational precincts 16

Electricity tariff 71 75

Emergency lighting 51 83

Emphasis 3

Entrance porch 17

Entrances 8 16

Equipment 58

Escalators 9

Escape lighting 52 83

Escape route 52

Exits 15 52

Extra-low voltage 83

F

Facades 16 45 51

Features 43

Filter 48

Flags 32

Flicker 83

Floodlighting 10 43 75

Floodlighting design 76

Floodlights 63

Flower beds 25

Foot-bridge 20 24

Footpath 83

Footpaths 20

Forecourts 19

Foundations 63

Fountains 33

G

Garage 19

Gardens 24

General lighting 83

Glare 7 83

H

Hazardous environment 83

Index Terms Links


Health care 14

Height/offset ratios 77

High mounted systems 13 41

Highlighting 4 30

Hiring 75

Hoardings 38

Hospitals 14 54

Hotels 18 54

I

Illuminance 6 83

Illuminated 38

Illumination 83

Illuminations 35

Incandescent lamp 83

Indirect lighting 83

Ingress-protection 83

Inverse square law 83

lP 62 83

Isolux curve 83

J

Jet 33

K

Key 3

L

Lamp depreciation 72

Lamps 58 83

Landscape 58

Landscape design 80

Landscapes 24

Light loss factor 83

Lighting design lumens 84

Linkways 14

Loading 10

Loading areas 14

Local lighting 84

Lorry parks 10 12

Louvre 84

Index Terms Links


Low mounted systems 13 41

Low pressure sodium 15 58

Lumen 84

Lumen method 76

Luminaire 84

Luminaire depreciation 73

Luminaires 61

Luminance 6 84

Luminous efficacy 59 84

Luminous flux 84

Luminous intensity 84

Luminous intensity distribution 84

Lux 84

M

Maintenance 6 72

Maintenance factor 73 84

Management 75

Marshalling yards 27

Masts 65

Memorials 30

Minimum illuminance 84

Modelling 4

Modern 47

Monuments 30

Motels 18

Mounting height 84

Music stands 36

N

Notice boards 16

O

Offices 9 47 54

Outdoor work 12

P

Parks 24

Pathways 7 8 20 24

Pavement 7

Pedestrian areas 7

Index Terms Links


Perimeter floodlighting 77

Perimeter lighting 9

Platform 14

Pools 33

Pop 36

Poster panels 38

Public buildings 7 8 16 17

54

Pump areas 19

R

Railway 14

Recreational 17

Reflectance 6 51 76 84

Reflector 84

Reflector lamp 84

Refuse 18

Restaurants 18

Restrike time 59 65

Retail 7 54

Rhythm 3

Roads 10 56

Rock shows 36

Rubbish 18

Rule of three 10

Run-up time 59 65

S

Scale 3

Schools 16 54

Sculptures 29

Security 9 10 53

Self-contained system 53

Service station 19

Shopping precincts 7

Shrubs 27

Signs 16 38

Silhouette 25

Site survey 5

Son et lumiere 37

Spires 50

Sports 16

Index Terms Links


Spotlighting 30

Stained glass 49

Stairways 7 20

Standby lighting 84

Stations 14

Statues 29

Steeples 50

Stepped areas 20 52

Storage 12

Structures 27 43

Subways 20

Sundials 31

Supports 65

Symmetric distribution 84

T

Timetable 14

Towers 13 28 50 65

Transmittance 84

Trees 24 25 26

Tungsten halogen lamp 60 85

Tunnel 23

U

Uniformity ratio 85

Unity 3

Unloading 10

Utilisation factor 84

Utilisation factors 76

V

Vandalism 20 53

Viaducts 27

Visual environment 85

Visual field 85

W

Walkways 7 8 20 24

Waste light factor 85

Water 24 33

Windows 49

Index Terms Links


Z

Zonal flux 79

Zonal flux diagram 85

Documents

CIBSE Lighting Guide LG6:1992 "The Outdoor Environment"