Presentation - Lighting Code

8/11/2019 Presentation - Lighting Code

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LIGHTING SYSTEM AS PER CODES: NBC AND

CIBSE GUIDELINES

By.Gulrez & Hemant kumar


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INTRODUCTION

lighting design is a field within architecture and architectural

engineering that concerns itself primarily with the illumination of

buildings. The objective of architectural lighting design is to obtain

sufficient light for the purposes of the building, balancing factors ofinitial and operating cost, appearance, and energy efficiency.


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LIGHTING AND HUMAN PERFORMANCE

Lighting enables humans to go about their lives, including work and play,

as effectively as possible. It provides for our visual needs, and also safety

and security. Lighting also has strong social and emotional significance.

Human needs are first and foremost. Since it's difficult to accomplish much

when we cantsee well, itsfairly obvious that lighting is crucial to human

performance.

Illumination levels for different tasks are recommended to be achieved

either by daylighting or artificial lighting or a combination of both.

Climatic factors which normally help in deciding the orientation of the

buildings to get desirable benefits of lighting inside the buildings.


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Principles of Lighting

Good lighting is necessary for all buildings and has three primary aims.

To promote work and other activities carried out within the building;

To promote the safety of the people using the building;

To create, in conjunction with the structure and decoration, a pleasing

environment conducive to interest of the occupants and a sense of their

well-being.


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Realization of these aims involves:

Careful planning of the brightness and colour pattern within both the working areas

and the surroundings so that attention is drawn naturally to the important areas,

detail is seen quickly and accurately and the room is free from any sense of gloom

or monotony .

Using directional lighting where appropriate to assist perception of task detail and

to give good modeling;

Controlling direct and reflected glare from light sources to eliminate visual

discomfort;

In artificial lighting installations, minimizing flicker from certain types of lamps and

paying attention to the colour rendering properties of the light;

Correlating lighting throughout the building to prevent excessive differences

between adjacent areas so as to reduce the risk of accidents; and installation of

emergency lighting systems, where necessary.


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Planning the Brightness Pattern

The brightness pattern seen within an interior maybe considered as

composed of three main parts

The task itself,

Immediate background of the task and

The general surroundings of walls, ceiling, floor, equipment and

furnishings.

Where work takes place over the whole utilizable area of room, the

illumination over that area should be reasonably uniform and it is

recommended that the uniformity ratio (minimum illuminance divided by

average illuminance levels) should be not less than

0.7 for the working area.


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Recommended Values of Illuminance

S.NO Types of interior or activity Range of service

illuminance in lux

Quality class of

direct glare

limitation1 Public rooms, halls 200-300-500 1

2 Auditorium 50-100-150

3 Lecture theatres 200-300-500

4 library 200-300-500

5 corridors 50-100-150

The illumination levels recommended in Table are to be maintained at all

time on the task. As circumstances maybe significantly different for different

interiors used for the same application or for different conditions for thesame kind of activity.

visual task is required to be carried out throughout an interior, general

illumination level to the recommended value on the working plane is

necessary;


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The precise height and location of the task are not known or cannot be

easily specified, the recommended value is that on horizontal plane 850

mm above floor level

Glare

Excessive contrast or abrupt and large changes in brightness produce the

effect of glare. When glare is present, the efficiency of vision is reduced andsmall details or subtle changes in scene cannot be perceived.

a) Direct glare due to light sources within the field of vision,

b) Reflected glare due to reflections from light sources or surfaces of

excessive brightness, and

c) Veiling glare where the peripheral field is comparatively very bright.


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Glare can be minimized by shielding the open sky from direct sight by

louvers

external hoods or deep reveals,

curtains or other shading devices

by cross lighting the surroundings to a comparable level.

A gradual transition of brightness from one portion to the other within the

field of vision always avoids or minimizes the glare discomfort.

Lighting for Movement about a Building

Most buildings are complexes of working areas and other areas, such as

passages, corridors, stairways, lobbies and entrances. The lighting of all

these areas should be properly correlated to give safe movement within the

building at all times.


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Corridors, passages and stairways

Accidents may result if people leave a well-lighted working area and pass

immediately into corridors or on to stairways where the lighting is

inadequate, as the time needed for adaptation to the lower level may be too

long to permit obstacles or the treads of stairs to be seen sufficiently

quickly.

Entrances

People entering a building will be adapted to the very high levels of

brightness usually present outdoors and there is risk of accident if entrance

areas, particularly any steps, are poorly lighted

Provision of window to give adequate light

supplementary artificial lighting should be installed to raise the level of illumination

to an appropriate value.

At night it is desirable to Any entrance steps to the building should be well-lighted

by correctly screened fittings.


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Daylighting

The primary source of lighting for daylighting is the sun. The light received

by the earth from the sun consists of two parts, namely, direct solar

illuminance and sky illuminance.

For the purposes of daylighting design, direct solar illuminance shall not be

considered and only sky illuminance shall be taken as contributing to

illumination of the building interiors during the day.


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The recommended design sky illuminance values are

6800 lux for cold climate,

8000 lux for composite climate,

9000 lux for warm humid climate,

9000 lux for temperate climate and

10500 for hot-dry climate.

For integration with the artificial lighting during daytime working hours an

increase of 500 lux in the recommended sky design illuminance for

daylighting is suggested.

Components of Daylight Factor

Daylight factor is the sum of all the daylight reaching on an indoor referencepoint from the following sources:

a) The direct sky visible from the point,

b) External surfaces reflecting light directly to the point

c) Internal surfaces reflecting and inter-reflecting light to the point.


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Sky Component (SC)

A. The recommended sky component level should be ensured generally on the

working plane at the following positions:

At a distance of 3 m to 3.75 m from the window along the central line perpendicular

to the window,

At the centre of the room if more appropriate, and

At fixed locations, such as school desks, black-boards and office tables.

B. The daylight area of the prescribed sky component should not normally be less

than half the total area of the room.


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Artificial Lighting

Artificial lighting may have to be provided

a) where the recommended illumination levels have to be obtained by

artificial lighting only,

b) to supplement daylighting when the level of illumination falls below the

recommended value, and

c) where visual task may demand a higher level of illumination.

Selection of the light sources and luminaires

The selection of light sources and lurninaires depends on the choice of

lighting system, namely, general lighting, directional lighting and localized or

local lighting.


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Determinat ion of the lum inous f lux

a) The luminous flux ($) reaching the working plane depends upon the

following:

1) lumen output of the lamps,

2) type of lurninaire,

3) proportion of the room (room index) (k,),

4) reflectance of internal surfaces of the room,5) depreciation in the lumen output of the lamps after burning their rated life,

6) depreciation due to dirt collection on luminaires and room suface.

b) Coeff ic ient o f Uti l izat ion or Uti l izat ion Factor

The values of the reflection factor of the ceiling and of the wall are as follows:White and very light colours 0.7

Light colours 0.5

Middle tints 0.3

Dark colours 0.1


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c) Calculation for determining the lumino us f lux


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Artificial Lighting to Supplement Daylighting

The need for general supplementary artificial lighting arises due to diminution of

daylighting beyond design hours, that is, for solar altitude below 15or when dark

cloudy conditions occur.

The need for supplementary lighting during the day arises, particularly when the

daylighting on the working plane falls below 100 lux and the surrounding luminance

drops below 19 cd/m2.


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Energy Conservation in Lighting

A substantial portion of the energy consumed on lighting maybe saved by

utilization of daylight and rational design of supplementary artificial lights.

Efficient luminaire also plays an important role for energy conservation in

lighting. The choice of a luminaire should be such that it is efficient not only

initially but also throughout its life. Following luminaries are recommended

for different locations:For offices semi-direct type of luminaries are recommended so that both the work

plane illumination and surround luminance can be effectively enhanced.

For corridors and staircases direct type of luminaries with wide spread of light

distributions are recommended.

In residential buildings, bare fluorescent tubes are recommended. Wherever the

incandescent lamps are employed, they should be provided


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Presentation - Lighting Code