www.cymru.gov.uk

Renewable energy and your historic building

INSTALLING MICRO-GENERATION SYSTEMS:

A GUIDE TO BEST PRACTICE

Key points to consider Solar hot-water panels

Solar electric(photovoltaics)

Heat pumps Micro wind tur-bines

Biomass Hydroelectric

Wherever possible, equipment should be installed away from the mainhistoric building or key feature of a site. Principal elevations or dominantroof slopes should be avoided.

• • • • •

Consider structural impact of heavy equipment on a historic building. • • •Consider impact on the setting of a historic building or monument. • • • • • •Consider cumulative visual impact of more than one installation on abuilding or group of buildings. • •

Consider impact of colour, texture and finish of equipment against thefabric of a historic building. • • •

Excavation or drilling work required to install pipes or cables may disturb buried archaeology. Seek advice from your regional archaeological trust.

• • • • • •

Storage batteries require the protection of a well-ventilated room or shed away from living areas where there is no health risk and no danger of damaging the historic fabric of a building.

• • •

When installing cables or pipes in a building, choose routes that will cause the least amount of damage. • •

Ensure that equipment is easily accessible for future maintenance with-out disturbing the fabric of a historic building; also, that it can be removed or replaced without causing damage.

• • • • •

Consider environmental impact on natural habitats. Seek advice from the Countryside Council for Wales or Environment Agency. • • • • • •

Discuss proposals with the planning and building control sections of your local authority at an early stage to check whether any form of consent is required.

• • • • • •

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Contents

Introduction 3

Types of micro-generation technology 4Solar hot-water panels 4Solar electric (photovoltaics) 6Heat pumps 8Micro wind turbines 9Biomass 10Hydroelectric 10

Choosing a micro-generation system 12Location 12Energy needs 12Scale 12Cost 13Options 13

Minimizing the impact on the historic environment 14Siting 14Design 16Cumulative visual impact 16Structural impact 17Building interiors 17Buried archaeology 18Maintenance and removal 18Wildlife 18

Planning controls, building regulations and the need for consent 19

Energy conservation and alternatives to micro-generation 20

3

Introduction

At the mention of renewable energy,usually the first thing we think of is largewind farms or hydroelectric schemesproducing enough electricity to servehundreds, if not thousands, of homes and businesses. But interest is alsogrowing in the use of micro-generationsystems serving individual or small groupsof buildings. Micro-generation is theproduction of heat, electricity or both ona small scale from a low carbon source.Many of the technologies use renewablesources, such as solar and wind power,whilst others continue to use fossil fuels, but with greater efficiency thanconventional systems. Although manypeople have already installed micro-generation technologies in theirproperties, its use is set to becomeincreasingly popular. As a consequence,solar hot-water panels, domestic-sizedwind turbines and photovoltaic arrays(PVs) will be a far more common sight in the future.

There is no reason why owners of historic buildings should not considerthese changes. However, if you arethinking about installing a micro-generation system in a historic building, a conservation area, a historic park orgarden, an ancient monument or on an archaeological site, thought should be given to protecting the fabric orcharacter of the building or landscapeand its setting. The historic environment

is central to Wales’s cultural heritage andsense of identity and, as such, deservesour care and attention.

This guidance is not intended to providetechnical advice, which is already availablefrom organizations including the EnergySaving Trust (www.energysavingtrust.org.uk).Instead, its purpose is to encourage localplanning authorities and owners ofhistoric buildings and sites, as well as theinstallers of micro-generation equipment,to consider carefully the design and sitingof micro-generation systems. It shouldalso make people aware of the range ofopportunities and different solutions thatare available to help lessen the impact of micro-generation technology on the historic environment. By usingexamples of good practice Cadw hopes to demonstrate that the historicenvironment need not be excluded fromactions to secure a more sustainablefuture, but this should be achieved throughthe careful preservation and sympatheticmanagement of the historic environment.

Opposite: This hydroelectric powerhousehas been designed to fit into the landscapeby using a turf roof and local stone, andutilizing the natural land form.

Right: Here, solar panels in the roof are wellhidden behind the tower and hardly visiblefrom the street. Unless panels can be screenedlike this, avoid positioning them on principalelevations and prominent roof slopes. ©

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The Welsh Assembly Governmentis committed to taking action toreduce the emission of greenhousegases. Recognizing that micro-generation has a vital role to play in achieving this objective, the Welsh Assembly Governmentpublished the Micro-generationAction Plan for Wales in March2007 to promote the use of these technologies. It sets targetsfor the installation of 100,000micro-heating systems, 200,000micro-electricity systems, and 50 combined heat and power systems in Wales by 2020.

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Types of micro-generation technology

There are several types of micro-generation systems and an increasingvariety of products on the market. Asuccessful installation depends on thechoice and location of equipment takinginto account the architectural, historicor archaeological importance of a site.

SOLAR HOT-WATER

PANELS (SOLAR

THERMAL COLLECTORS)

Solar hot-water panels are the mostcommon type of micro-generationtechnology currently used due to their relatively low cost and ease of installation. They can be used toproduce hot water and, occasionally,for space heating. A domestic systemconsists of three main components: asolar collector, a heat-transfer system,which may include a pump to circulatewater, and a hot-water cylinder. Thecylinder may be a separate oneserving just the solar hot-water systemor, more commonly, it may combinesolar and more conventional forms of hot-water production.

There are two main types of solarpanel: flat plate collectors, whichconsist of an absorber plate with a transparent cover, and evacuatedtube collectors, which consist of a

row of glass tubes each containing an absorber plate. Evacuated tubecollectors are generally more efficient, but they tend to be more expensive, more fragile, and arguably, more conspicuous.

A domestic system will require a solar collector covering roughly 4 square metres, although theindividual panels do not necessarilyhave to be located together. This can help to reduce the overall visual impact in situations where

the collector may otherwise be anoverly dominant feature. A largecollector on a small roof slope maylook out of scale.

Solar collectors are most frequentlysited on roof slopes with a south-westto south-east orientation and at apitch of 30–50 degrees. Nevertheless,they can be installed at a very shallowpitch just steep enough to allowrainwater to wash off dirt and debris. In the case of evacuated tubecollectors, it is also possible to install

Re-roofing may provide an opportunity to install an integrated flat plate solar collector in a discreet location. This type of system can blend into the roof slope better than a framedpanel that stands proud of the cladding, but remember to store sufficient slates or tiles tore-cover the area when the panel is removed at the end of its life. This avoids the problemof trying to find matching materials.

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TYPES OF MICRO-GENERATION TECHNOLOGY 5

them vertically on a wall. Care doesneed to be taken when installingpanels on a lead roof. The design andlocation of fixings and pipework musttake account of the natural expansionand contraction of lead over time.

Flat plate collectors can be installedflush with the plane of the roof, butmost are installed in frames that stand proud of the roof cladding byup to 125mm, which may make themquite conspicuous. However, bothtypes of fitting have their advantages. Raised panels are usually fitted withinaluminium frames, which are attachedto the roof using roof-tile hooks that slip under the slates or tiles and are fixed to the rafters. The onlypenetrations through the roof are toaccommodate the pipes that connectthe solar collectors to the hot-watertank. This involves minimal externalalteration to the building and theequipment is very easily removed at the end of its life.

Conversely, flush-fitting solar panels are integrated into the roofstructure. They can potentially blendin better, but installation requires the removal of the roof claddingbeneath the panels. This is unlikely tobe acceptable where the roof forms part of the special interest of a listedbuilding, but may be acceptable if re-roofing is required. The additionaldepth of the panel should beaccommodated through omission of the battens to which the slates or tiles are normally fixed, rather than trimming the roof timbers orremoving rafters. Flashing will berequired around the panels in orderto ensure a good weather-tight seal.

These flat plate solar collectors are installed in a hidden roof valley at the back of thebuilding. The dark coloured frames help to further reduce the visual impact.

Installing solar panels at a low angle on a flat roof can be a good choice for a historic building. However, care is needed when installing them on a lead roof as the lead sheet may tear if it is not allowed to expand andcontract naturally.

There will usually be more than one possiblelocation for solar panels, so consider all of the options, even if some do not providethe optimum conditions. Evacuated tubecollectors are more efficient than flat platecollectors and they can be installed verticallyon a wall if a suitable location can be found.

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6 TYPES OF MICRO-GENERATION TECHNOLOGY

SOLAR ELECTRIC

(PHOTOVOLTAICS)

In a photovoltaic system, light hitting thesilicon in a solar photovoltaic (PV) cell is converted directly into electricity. Thegreater the intensity of light, the greaterthe flow of electricity. Individual PV cells are connected together to form amodule. Modules are linked to form aPV array. After conversion from directcurrent (DC) to alternating current(AC), the power generated by the cellsis carried into the building’s normalelectrical system to work alongside theexisting electricity supply. Excess powershould ideally be exported to theNational Grid to help offset the cost ofbuying electricity back during the nightand at other periods of low electricity

The area of a typical domestic-sized PV system will be 10–15 square metres.These units are less obtrusive than manydue to their colour and simple design.

Try to install solar panels and photovoltaic (PV) arrays as free-standing units if possible.The impact of this installation could have been further reduced by choosing a darkcoloured frame and providing some soft landscaping.

These PV arrays have been installed as bespoke free-standing units that stand on a flat roof hidden behind a parapet wall.

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With a little thought, PVs can easily beintegrated into the design of new gardenstructures, such as this pergola.

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TYPES OF MICRO-GENERATION TECHNOLOGY 7

generation. Alternatively, it can bestored in batteries.

Crystalline PV cells are encapsulated in a transparent, insulating polymer with a tempered glass cover. Amorphoussilicon cells are less efficient thancrystalline cells, but they can bedeposited on a range of materials, making them suitable for curved orflexible surfaces. The technology istherefore very versatile and PV arrayscome in a variety of shapes and colours. They can be used as opaque wall cladding or as transparent cells to replace glass.

Modules may be framed, similar tosolar hot-water collectors, for installationon roofs or as free-standing units. Some manufacturers also produce smallmodules that are used as roof claddinginstead of slates. The appearance ofthese does vary, but the choice isincreasing as manufacturers strive toreplicate the appearance of naturalslate. Nevertheless, unless discreetlylocated they will rarely be a suitablesubstitute for stone tiles, pegged slatesor slates laid in diminishing courses.

PV arrays need a shade-free site orientated between south-east and south-west. Shade on any part of the array will greatly reduce theperformance of the whole unit. The ideal pitch is 30–40 degrees, but this canbe reduced to as little as 15 degrees,enabling arrays to be installed on flatroofs or behind parapet walls. As withsolar hot-water panels, care must betaken when installing PVs on lead roofs.

A typical domestic system of 10–15 square metres will supplyapproximately half of a household’sannual electricity demand.

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Above left and right: Amorphous silicon cells can be used to coat glass. This example is ona new building, but this type of glass set into a well-designed frame could be used to goodeffect on historic buildings where large areas of new glazing are proposed, such as athreshing barn that is being converted to domestic use.

Above and left: There are some goodexamples of PV roof cladding that emulatethe look of natural slate and the technologyis constantly evolving. The slates picturedhave the advantage of being thin and non-reflective, though rarely will they be a suitable substitute for Welsh slate on a principal roof slope. PV

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8 TYPES OF MICRO-GENERATION TECHNOLOGY

HEAT PUMPS

Heat pumps work on the principle of absorbing heat from one place and releasing it in another. Heat iscollected from one of three sources:the air, the ground or a body of water.The heat is transported around asealed system by a refrigerant, whichis circulated by a compressor. Thesystem operates in a continuous cycle while the pump is running.

Heat pumps can be used to supplyhot water ; they can also be used forspace heating, but work best in a well-

insulated building. Heat pumps aremost frequently connected to anunder-floor heating system and theircontinuous use allows a build up of residual heat that requires littletopping up. They may also beconnected to oversized or fan-assisted radiators. Some types of heat pump can be used in reverse to provide air conditioning.

Ground-source heat pumps are the most common type of heat pumpinstalled in the UK at present. The initialset-up cost is higher than an air-sourceheat pump, but they are more efficient.The heat is collected in a series of

narrow boreholes approximately 100 metres deep, or alternatively, in a horizontal ground loop installedaround 1.8 metres below the surfaceof the ground, where the temperatureis relatively stable. Care needs to be taken in siting a ground-source heat pump as the excavation or drillingwork required to install the pipescould disturb buried archaeology. If you are connecting a ground-sourceheat pump to an under-floor heatingsystem this can also have implicationsfor archaeological remains buriedwithin a building. Minimal disruptionwill be caused where the floors havepreviously been replaced or need to be removed to address problemssuch as damp.

Air-source heat pumps are lesscommon than ground-source heatpumps, but they are well suited tocoastal areas where the ambienttemperature is higher. They occupy a relatively small space: the heatexchanger usually comes in a metalbox approximately 1 metre high. Theymust be sited in a well-ventilated

Below left and right: This air-source heat pump is installed on a discreet flat-roofed areaand is barely visible from anywhere on or around the building. It was installed to providehot water for a new bathroom as an alternative to extending the existing hot-water system,which would have disturbed the original 1930s interior.

TYPES OF MICRO-GENERATION TECHNOLOGY 9

location, such as on a flat roof or on a wall with a suitable circulation area.

Whatever type of heat pump isused, an energy source will be neededto operate the compressor. Thisenergy input could be provided byanother type of micro-generationsystem, such as a photovoltaic array.

MICRO WIND

TURBINES

Most electricity generating turbineshave between two and five bladesaround a central hub. The motion of the blades turns a rotor, convertingthe kinetic energy of the wind intoelectrical energy. The amount ofpower generated depends on the‘swept area’. Therefore, the larger the area the greater the potentialoutput. A domestic system wouldtypically produce 1–6 kilowatts, but smaller systems can be used to recharge batteries or to powerlow-voltage equipment.

Ideally, the system should beconnected to the National Grid,allowing excess electricity to be sold.In locations where connection is notfeasible, batteries can be used to storeexcess energy until it is required.

Turbines must be sited in areasonably exposed location andwork best at a height where windspeeds are high and there are noobstructions from buildings, trees or other features that would causeturbulence. Consequently, they areoften difficult to integrate successfullyinto an urban environment and aremore suitable for rural locations. The Energy Saving Trust advises that turbines should be consideredonly where the local annual averagewind speed is 6 metres per second.

A turbine may be mounted on a pole or a lattice tower as a free-standing unit. The pole or tower willneed to have reinforced concretefoundations and a cable connecting it

to the building to which it is to supplyenergy. Cables are usually buried inthe ground at a depth of no less than0.5 metres in order to protect themfrom damage. Alternatively, a turbinemay be fastened to a bracketmounted on the wall of a building sothat it stands up above the roofline.

Below: Consider carefully the location ofburied cables or pipes to avoid damagingarchaeological remains. The installation ofthis horizontal ground loop shows thedepth of the trench required to put in aground-source heat pump.

Bottom: Wherever possible, relay theoriginal floor on top of an under-floorheating system to avoid damaging thecharacter of the building. Before liftingfloors, seek advice from your regionalarchaeological trust about the possibility of finding buried archaeology.

Top: Small-scale wind turbines cansometimes be fastened to a bracketattached to a building, but make sure first that the building can withstand the additional loading.

Above: Choose a site that allows the height of a free-standing turbine to be aslow as possible and try to locate it so thatwhen viewed from sensitive locations it will be seen against a landscape backdrop.

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10 TYPES OF MICRO-GENERATION TECHNOLOGY

B IOMASS

A small-scale biomass systemgenerates heat for hot water andspace heating by burning organicmatter. Although carbon dioxide is released in the process, this isbalanced by the amount absorbedduring the growth of the plant matter.This gives the system potential to be close to carbon neutral in use.

Whereas large systems may usematerials such as municipal or

agricultural waste to produce electricityas well as heat, domestic appliancesusually use wood pellets, wood chips or logs. A domestic biomass system isa very quiet, efficient and controllablesource of heat. However, as with othersolid fuel systems an alternative methodof heating water, such as an electricimmersion heater or solar panels, islikely to be needed during the summermonths and at other times of lowdemand when it is not viable to keepthe boiler operating.

Biomass can be used in either astand-alone system to heat a singleroom, or can be connected to a central-heating and hot-water system. It can alsobe used as a district heating system toserve larger sites or groups of buildings.Schemes such as the conversion of a farm complex to residential orcommercial use may be particularlysuited to this type of system, where a centralized boiler-house produceshot water which is circulated via anetwork of flow and return pipes.

Wood-chip and wood-pelletboilers can be fitted with automatedfeed hoppers. Space will be requiredto store the fuel and to keep it dry,and the system will also need a flue to remove waste gases. With a smalldomestic appliance it may be possibleto install the flue in an existing chimney.

HYDROELECTRIC

Hydroelectric schemes have a verylong history of use and many watermills are listed for their architecturalor historic interest. In a hydroelectricsystem, running water turns a turbine

Left and below: Two biomass boilers of different scales: the one above is fitted into a domestic fireplace, whilst the other is sited in an outbuilding andserves several properties.

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TYPES OF MICRO-GENERATION TECHNOLOGY 11

to produce electricity. The amount ofenergy that can be released dependson the amount of water flowing persecond, the flow rate and the heightthat the water falls, as well as theefficiency of the system. The electricityproduced can be supplied directly orthrough batteries using an inverter toconvert the current from DC to AC.Alternatively, it can be connected tothe National Grid.

A system will typically consist of an intake incorporated into a weir to divert the watercourse; a leat or penstock pipe; a powerhouse,monitored by a control panel, in whicha turbine and generator convert thepower of the water into electricity; anoutflow pipe to release the water backinto the watercourse; and undergroundcables or overhead lines to transmitthe electricity to the point of use.

The number of sites with a suitablewatercourse is limited, but, where there is a suitable resource, a smallhydroelectric system can be a cost-effective option. Historic mill sites mayprovide suitable locations for newhydroelectric installations, althoughconsideration needs to be given to the archaeological impact of any newworks. As with other types of micro-generation equipment, a back-up powersupply may be needed to compensatefor seasonal variations. In most cases a Water Abstraction Licence will berequired from the Environment Agency.The Environment Agency and theCountryside Council for Wales will beable to offer advice on any mitigationmeasures, such as the provision of fishladders, to offset the impact on theecology of a watercourse.

Left: The hydroelectric equipment neededto run this system is contained in a smallpowerhouse located next to the stream,which provides the source of energy.

Below: Historic mill sites, such as DyfiFurnace, could once again be utilized for amodern hydroelectric scheme to help meetthe energy needs of the local community. ©

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Choosing a micro-generation system

LOCATION

When choosing a micro-generationsystem it is important to understandyour energy needs; it is equallyimportant to have a clear understandingof the architectural, historic orarchaeological significance of thelocation of the installation. Thissignificance may derive from evidence of past human activities which haveshaped the landscape, such as farming or mineral extraction. Alternatively, itmay arise from the quality of placeunique to our historic towns and villages.A historic building might be of specialinterest because of its original function,its design and materials or the way it has been adapted over time. Even smalldetails, such as internal fittings, can beimportant. By ensuring that these factorsare properly understood and taken into account the impact of installationcan be kept to a minimum and anyconsent needed, such as planningpermission or Listed Building Consent, is more likely to be forthcoming.

ENERGY NEEDS

No single micro-generation system is likely to supply all of the heat and electricity needed in a building,

although combinations of technologiescan be designed to do so. A solar hot-water system, for example, willprovide one third to half of the hot water needed for a domesticproperty year round. By also installinga biomass system, hot water as well as space heating can be providedduring the winter months when solar hot-water panels are likely to be less efficient.

It is also important to remember that in some cases the amount of heat or electricity generated may not be constant and peak productionmay not coincide with peak demand.Energy generating systems, includingphotovoltaic arrays and wind turbines,can produce more electricity than isrequired at the time of production. In such cases, the system can beconnected to the National Grid,allowing excess energy to be sold during peak production andbought back at other times. Whereconnection is not possible, batterystorage will help to match energygeneration with demand.

SCALE

The scale of the energy requirementwill also help to determine what typeof system best suits your circumstances.

Energy may be required to power a single use, such as a security light or an electric fence, or to meet theenergy needs of an individual buildingor a group of buildings. District heatingsystems and combined heat and powersystems can present opportunities for using technology that may not be viable on a smaller scale, such asutilizing waste heat from industrialprocesses or using the stored energy in organic matter (biomass) or water (hydroelectric).

In a district or community heatingsystem, a central boiler produceshot water, which is circulated tonearby buildings through a networkof pipes. The network may include asfew as two or as many as hundredsof properties. This arrangement canbe particularly useful for groups ofhistoric buildings, such as convertedfarm complexes, as only one boilerand flue are needed.

A combined heat and power systemproduces heat for space heating orhot water, as well as electricity. It canserve one building or supply a localarea. These systems are very efficientand use a variety of fuels, includingwood pellets.

CHOOSING A MICRO-GENERATION STSYEM 13

COST

Choosing a micro-generationtechnology that will have a minimaleffect on the historic environmentneed not necessarily cost more or compromise the efficiency of a system. The initial cost of micro-generation equipment andexpenditure on installation andongoing maintenance needs to beconsidered against the amount of heat or energy that the system canrealistically produce.

Installing micro-generation systemsat the same time as other works areundertaken can help to offset some of the initial cost, thereby reducing the payback period, as well as reducingthe potential for damaging a historicbuilding or underground archaeology.For example, the pipework for aground-source heat pump could beinstalled when preparing foundationsfor an extension.

OPTIONS

In order to promote good practice, the UK Micro-generationCertification Scheme (MCS) has been established to certifyindependently on-site energyproduction technologies and installers.The scheme is designed to givegreater protection for consumers and includes a mechanism for dealing with complaints. MCSregistered installers must give accurate predictions of the likelyenergy outputs of an installation,which should be measured against the possible impact on a historic place or building.

Further information on thisscheme, as well as advice on choosing a micro-generation system, is available from the Energy Saving Trust — an organization funded by thegovernment to provide free, impartial advice to householders and communities. Installers who offer a limited range ofequipment may not be able toprovide this initial advice or to suggest the best solution for a particular situation. The trust will also be able to suggest possible sources of grant assistance and to provide a list of installers.

It is also advisable to discussproposals with the planning andbuilding control sections of the local authority at an early stage to check whether any form of consent is required.

1. This Grade I listed house and associatedbuilding complex is heated using a biomassboiler connected to a district heatingsystem. The hot water is pumped aroundthe site through an underground heat main.

2. The wood used as fuel in the biomassboiler is sourced from the estate woodlandand chipped on site.

3. A derelict outbuilding was restored for use as a fuel store and to house theautomated wood-chip boiler.

4. The only outward sign of the boiler is the small stainless-steel flue projectingabove the rear roof slope of the large outbuilding.

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Once you have chosen the mostsuitable form of micro-generationtechnology for your historic building or environment, you should make further efforts to ensure it is well integrated.Although every historic building will present different options to minimize the impact, the following are key issues which should be considered for every installation.

SITING

Wherever possible, micro-generationequipment should be installed awayfrom the main historic building or key feature of a site. It will rarely beacceptable to install equipment on theprincipal elevation of a listed buildingor on a dominant roof line. It ispreferable to install solar panels andPV arrays on outbuildings — such asgarages — or as free-standing units

(with good insulation of pipework to help minimize heat loss).

Some types of micro-generationtechnologies require the use ofstorage batteries to store excesselectricity. These are potentiallyhazardous and relatively bulky and will require the protection of a well-ventilated room or shed away fromliving areas so as not to pose a healthand safety risk and also where there is no danger of damaging the historicfabric of a building.

In addition, consideration should be given to the space required for

Minimizing the impact on the historic environment

These free-standing solar hot-water panels have been carefully sited so as to blend in withthe surrounding rockery and planting scheme.

The valley between pitched roofs provides an ideal location for theseevacuated tube solar collectors. They are bolted to the rafters and the onlypenetrations through the roof are toaccommodate the water pipes. It will be relatively easy to remove the systemwhen it reaches the end of its life and to restore the roof covering.

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MINIMIZING THE IMPACT ON THE HISTORIC ENVIRONMENT 15

the storage of fuel, in the case of a biomass system especially.

If installation away from the mainhistoric building or feature of a site is not feasible try to make use of lessprominent parts of the building —such as hidden roof valleys or rearextensions — or try and screenequipment from view by locating it behind parapet walls. It might bepossible to site an air-source heatpump to the rear of a building, in aservice area, or on a flat roof where it would have the least visual impact. It might be the case that certainmicro-generation technologiesbecome less energy efficient whenplaced in a more discreet location. For example, solar panels may notbenefit from full sunlight or be at the optimum orientation and pitch.You could overcome this problem by increasing the size of the panels.

The impact of micro-generationtechnologies on the setting of ahistoric building or monument is also important. With care, most types of free-standing equipment may be successfully integrated intothe landscape or screened from view.However, this integration is muchmore difficult to achieve with microwind turbines. A well-chosen siteshould allow the turbine to be viewedagainst a landscape setting rather thanopen sky, and also for its height to be as low as possible. In addition, thepotential impact of noise, vibrationand shadow flicker on your andneighbouring properties should beconsidered. In sensitive locations itmight be preferable to use otherforms of renewable energy.

This ground-source heat pump is connected to an under-floor heating system and is sited in the service area to the rear of a converted stable block so as to be as discreet as possible.

The control equipment for the ground-source heat pump at this site is housed in a purpose-built stone outhouse that echoes the design and materials used in the church itself.

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16 MINIMIZING THE IMPACT ON THE HISTORIC ENVIRONMENT

DESIGN

The colour, texture and finish ofequipment in comparison with thebackground material will all influencehow noticeable the micro-generationsystem is once installed. The design ofearly types of equipment paid little orno attention to appearance or visualimpact, but this is beginning to change.The design and colour of visibleancillary equipment, such as pipes,frames, stands or poles, is just asimportant as the micro-generationequipment itself.

If installing equipment on a historicbuilding, think about the characteristicsof the building’s structure andarchitectural ‘vocabulary’ as this

may give clues as to what is likely tobe successful visually. Elevations may be symmetrical or have a stronghorizontal or vertical emphasis. Echoingsuch features may help installations to blend into their surroundings,whereas a strong contrast may make them more conspicuous.

Scale is also an importantconsideration. Whereas a large buildingmay be able to accommodate acomparatively large area of solarpanels, the same installation on a smallvernacular cottage may overwhelm

the scale and character of the building.However, it may be possible to locatethe panels in separate locations inorder to spread the impact.

CUMULATIVE

VISUAL IMPACT

A single installation is unlikely to meet the total year-round demand for heat and electricity at a building or site. Complementary systems are likely to become more

A new shed clad with corrugated iron sheets was built on the lower end of this cottage onthe site of a former outbuilding. It houses a biomass boiler and its simple design and smallscale, together with the choice of materials and colour of the cladding and flue all help toensure that the extension is in keeping.

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MINIMIZING THE IMPACT ON THE HISTORIC ENVIRONMENT 17

commonplace in the future. Whereas most buildings are capableof accommodating a degree ofchange, multiple installations may have an unexpected cumulative visual impact.

This also applies to separatebuildings within a group. Conservationareas are designated so on the basis of their quality of place, theresult of many factors including the grouping and scale of buildingsand the relationship between buildings and spaces. Other types of designation include Historic Parksand Gardens, and World HeritageSites. However, the qualities that led to designation can easily beharmed unless the visual impact of micro-generation systems on

neighbouring buildings and the wider street scene and landscape is carefully considered.

STRUCTURAL IMPACT

Some types of micro-generationequipment can be very heavy. Whereequipment is to be mounted on theexterior of a building it is advisable to first obtain a structural survey froman appropriately qualified historicbuildings advisor to ensure that thestructure and historic fabric of thebuilding will not be damaged. This is particularly important if you areconsidering installing a wind turbineon an existing building, although inpractice, there will be few traditional

buildings where turbines are likely tobe acceptable because of their visualimpact. The structure on which theturbine is mounted must be capableof withstanding not just the weight of the equipment (up to 30 kilograms),but also the forces exerted on theblades, particularly during periods of high wind. Chimneys and infillpanels in timber-framed buildings are unlikely to be able to withstandthese additional stresses.

Solar panels and PV arrays can alsoadd a considerable amount of weightto a roof, particularly when they are used in addition to the existingcladding. The weight is carried by the rafters, which in many traditionalbuildings, especially vernacularcottages and agricultural buildings, are smaller than current standards.Whilst they are perfectly adequate to support the existing roof covering,they may not be capable of carryingthe additional dead weight or theuplift created by the wind.

BUILDING INTERIORS

When installing cables or pipes forsolar panels, PV arrays or heat pumpschoose routes that will cause the least amount of damage, even if they are less direct. It may be possibleto use existing conduits or to liftfloorboards that have previously been re-laid to minimize disruption.Try to locate elements as discreetly as possible and ensure that anyalterations are easily reversible.

Avoid cutting through structuraltimbers, such as floor joists, as this can

Above and left: The banks of solar panels serving the listed farmhouse andholiday cottage at this site are situated on the hillside behind the agriculturalbuildings and can only be seen at adistance. The robust scale and simple form of the installation is fitting in thislocation and does not detract from thesetting of the listed buildings.

18 MINIMIZING THE IMPACT ON THE HISTORIC ENVIRONMENT

weaken them. If chasing in cables or pipes, take care to avoid damaginghistoric items, such as panelling, plaster cornices and wall paintings, and to remember that features ofinterest may be hidden by lateradditions or decoration. Similarly, the excavation of floors to install an underfloor heating system candisturb archaeological remains within the building, such as evidenceof an open hearth in a medieval hall-house or the foundations ofpartition walls previously removed. If features are discovered during the installation work, stop immediatelyand seek advice from the localplanning authority.

Internal and external alterations to a listed building are likely to requireListed Building Consent, so it isessential to seek advice from the localplanning authority at an early stage.

BURIED

ARCHAEOLOGY

Systems that depend on buried cablesor pipes to connect the energy sourceto the place where the energy isrequired, such as free-standing solarpanels, ground-source heat pumps,and hydroelectric systems, have thepotential to damage undergroundarchaeology. Similarly, wind turbinesmounted on masts or lattice towerswill require substantial foundations of a metre or more in depth, whichmay disturb underlying features.

Areas that are more likely tocontain buried features of interest,

apart from known archaeological sites, may include historic town or village centres. In most cases it will be possible to balance the need to preserve archaeologicalfeatures with the desire to installmicro-generation systems. However,advice should be sought from therelevant regional archaeological trust. In addition, any works affecting a scheduled ancient monument will require Scheduled AncientMonument Consent and in such cases Cadw should be consulted at an early stage.

MAINTENANCE

AND REMOVAL

When installing a micro-generationsystem, it is important to ensure that the equipment is easily accessibleto allow for future maintenancewithout disturbing the fabric of a historic building. You must alsoensure that the equipment can be removed or replaced withoutcausing unnecessary damage. Try to minimize the damage, both at the time of installation and removal, by fixing into mortar joints rather than bricks or masonry, as repairs will be easier to undertake and less obtrusive. When a system hasreached the end of its useful life or simply needs replacing, ensure that any redundant equipment, cables, pipes and fixings are removed,and any damage made good usingmaterials appropriate to the building,such as lime mortar.

WILDLIFE

Many historic buildings and landscapessupport a variety of wildlife byproviding breeding and roosting sites,as well as feeding grounds. Manyspecies, including all bats and manytypes of birds, are protected in law.The Wildlife and Countryside Act1981 gives full protection to bats,making it illegal to intentionally kill, injure or handle any bat or tointentionally damage, destroy orobstruct access to any place that a bat uses for shelter or protection.Many historic buildings are home tobat colonies, which can be disturbedby work to roofs and attic spaces.Before undertaking any work that will affect a protected species, seek advice from the CountrysideCouncil for Wales on how to avoiddisturbing a natural habitat and tocheck whether a licence is required.

Similarly, seek the advice of theEnvironment Agency for any worksaffecting a watercourse in the case of hydroelectric technologies. In mostcases, a Water Abstraction Licencewill be required.

Opposite: The qualities that led to thedesignation of a conservation area, such asDolgellau, could be harmed if the visualimpact of multiple installations is notcarefully considered.

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Planning controls, building regulations and the need for consent

Before installing any micro-generationequipment check with the localauthority whether any form of consentis required. Even if you have beenoffered a grant do not assume that you will not need to obtain furtherpermissions. Approval may be requiredunder the Building Regulations. Theinstallation of some types of micro-generation equipment will also needplanning permission. Where proposalsaffect historic buildings or areas, the local planning authority will takeinto account the likely impact on the historic building. The impact onthe setting of the historic property is also a material consideration.

Works that would affect thecharacter of a listed building are likely

to require Listed Building Consent.Controls apply to both internal andexternal works whether or not theparticular feature affected is specificallymentioned in the list description. Thisprotection will usually extend to anyobject or structure fixed to the listedbuilding or located within its curtilage— an area of land attached to a houseand forming one enclosure with it. Thelatter may include ancillary buildings,garden structures and boundary walls.Advice on consent should be soughtfrom the local planning authority at anearly stage.

Any application for planningpermission or listed building consentwill need to be accompanied by a design and access statement. This will need to explain why a particularmicro-generation system and site have been chosen in favour of other options based on an assessmentof the differing impacts on theheritage asset.

At scheduled ancient monumentsconsent is required for any works thatwould have the effect of demolishing,destroying, damaging, removing,repairing, altering, adding to, floodingor covering up the monument.Applications should be submitted to Cadw and initial advice can besought from Cadw or the relevantregional archaeological trust.

FURTHER GUIDANCE

• Planning Policy Wales, Technical Advice Note 12: Design (June 2009)Can be downloaded fromwww.wales.gov.uk/topics/planning/policy/tans/tan12

• Welsh Office Circular 61/96,Planning and the HistoricEnvironment: Historic Buildingsand Conservation Areas(December 1996)

• Welsh Office Circular 60/96,Planning and the HistoricEnvironment: Archaeology(December 1996)Can be downloaded from theHeritage Policy Publicationssection of the Cadw website:www.cadw.wales.gov.uk

For hard copies of all publicationsplease contact the PublicationsCentre, National Assembly for Wales, Cathays Park, Cardiff CF10 3NQ, tel: 029 2082 3683, email:assembly-publications@wales.gsi.gov.uk

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Energy conservation and alternatives to micro-generation

Micro-generation is only one of the waysin which we can help to reduce carbonemissions. Other energy conservationmeasures that do not adversely affectthe character or fabric of a historicbuilding should be considered first andforemost. Behavioural changes are oftenthe simplest and cheapest options, yet the benefits can be profound. Actionscould include reducing the thermostatby one degree, closing curtains orshutters at night, using low-energy light bulbs and switching off electricalequipment when it is not in use.Physical alterations to a building mightinvolve installing loft insulation, draughtproofing or secondary double-glazing.However, as with any alteration, caremust be taken to protect the characterof a historic building and to ensurecompatibility with traditional buildingmaterials. It is also important to ensurethat buildings are properly maintained

and well ventilated. This will help tocontrol moisture levels and therebyreduce the amount of heat needed to achieve a comfortable living andworking environment. The greatestenergy efficiency will be obtained wheremicro-generation technologies formpart of a holistic approach to buildingmanagement. This applies as much to existing buildings as to new ones.

Although rare, there will be caseswhere a historic building or site is so sensitive that micro-generationequipment cannot be installed withoutcausing unacceptable harm to itscharacter. In this situation, as well asadopting energy-saving measures, someindividuals, businesses or organizationsmay also opt for voluntary carbonoffsetting. This is where greenhouse gas emissions are mitigated by thepurchase of carbon offsets. There are anincreasing number of companies offeringthis service, but one simple method ofoffsetting is switching to one of manyelectricity suppliers now offering a ‘greentariff.’ There are three basic types ofgreen tariff: for every unit of electricityyou buy the supplier guarantees to buy a set amount of electricity from arenewable source, the supplier helpsfinance the construction of renewableenergy projects, or the supplier helpssupport other environmental, carbonoffset or research projects.

Above left: Keeping windows in a goodstate of repair, fitting draught proofing and making use of heavy curtains or shutters can greatly improve their thermal performance. This can be further enhanced by the addition of well-designed secondary double-glazing.

Left: Sheep’s wool insulation in the roof space is just one of many ways toimprove the thermal performance of a historic building.©

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Contacts and sources of advice

Cadw, Welsh Assembly Government, Plas Carew, Unit 5/7 Cefn Coed, Parc Nantgarw, Cardiff CF15 7QQTel 01443 336000www.cadw.wales.gov.uk

Clwyd-Powys Archaeological Trust7a Church Street, Welshpool SY21 7DLTel 01938 553670www.cpat.org.uk

Dyfed Archaeological TrustThe Shire Hall, 8 Carmarthen Street,Llandeilo SA19 6AFTel 01558 823121www.dyfedarchaeology.org.uk

Glamorgan-Gwent Archaeological TrustHeathfield House, Heathfield, Swansea SA1 6ELTel 01792 655208www.ggat.org.uk

Gwynedd Archaeological TrustCraig Beuno, Garth Road, Bangor LL57 2RTTel 01248 352535www.heneb.co.uk

Energy Saving Trust Wales1 Caspian Point, Caspian Way, Cardiff Bay, Cardiff CF10 4DQTel 029 2046 8340 www.energysavingtrust.org.uk

Countryside Council for WalesMaes-y-Ffynnon, Penrhosgarnedd, Bangor LL57 2DWTel 0845 1306229www.ccw.gov.uk

Environment AgencyPO Box 544, Rotherham S60 1BY Tel 08708 506 506www.environment-agency.gov.uk

Local authorityPlanning department and/or Conservation Officer

© Cadw, Welsh Assembly Government (Crown copyright)First published 2010ISBN 978 1 85760 283 8Cover : Cottage with solar panel (© Iain Wright FBIPP)

The inclusions in this publication of any company, group or individual, or any product or service, should not be regarded as either a recommendation or an endorsementby Cadw, Welsh Assembly Government.

Cadw is the Welsh Assembly Government’s historic environment service, working for an accessible and well-protected historic environment for Wales.

This publication is available in alternative formats. For details pleasecontact Cadw at the address above or telephone 01443 336000.