energy efficient pools 3

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In-depth technology guide CTG009

Swimming poolsA deeper look at energy efciency


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Contents

Introduction 02

Energy consumption 03

Pool halls – space heating and ventilation 05

Pool water – heating and treatment 14

Lighting 19

Motors and pumps 21

Action checklist 22Next steps 23

Glossary 24


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01Swimming pools

Reducing energy use makes perfect business sense; it saves money, enhancescorporate reputation and helps everyone in the ght against climate change.

The Carbon Trust provides simple, effective advice to help businesses takeaction to reduce carbon emissions, and the simplest way to do this is to useenergy more efciently.

This technology guide introduces the main energy saving opportunitiesrelating to swimming pools and demonstrates how simple actions save

energy, cut costs and improve comfort for those who use the facilities.


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02 The Carbon Trust

Swimming pool halls consume more energy per unit area than almost any

other building type. In fact, they use ve times as much energy per squaremetre as ofces, which means extra vigilance in the design and operationof swimming pools is of the utmost importance.

Introduction

The range of facilities found in the wet leisure sectoris vast, from the smallest spa pool to a large Olympicsized facility. While all of these have quite differentenergy costs, the heating and treating of water in allswimming pools makes consumption patterns similar.

As such, the advice given in this publication is applicableto all wet leisure facilities, both indoor and outdoor.

This technology guide has been developed to helppool centre managers and operators ensure that energyis managed efciently in their swimming pools. Withthe complex range of associated building servicesand their considerable energy demand, it is importantthat opportunities for both carbon and cost savingsare highlighted.

All of the technologies discussed in this guide canyield signicant savings. This publication will also

help managers to:• Assess the potential for carbon savings and indicate

key areas for improvement

• Raise awareness of carbon emissions amongst staffand motivate them to reduce waste

• Appraise the overall energy performance of aswimming pool.

Who is this publication for?The advice in this publication will be useful to anyone

involved in the running of swimming pools, such asthose in sports and leisure centres, clubs, hotels orschools. This includes centre managers, energymanagers and key decision makers in pool facilities .

This guide contains detailed information aimed atthose with a real interest in implementation. It isexpected that readers will have prior knowledge andexperience of energy efciency and are familiar withthe basic advice given in the Carbon Trust’s sectoroverview publications.

Why reduce your carbon footprint?• Save money and increase prots

• Provide better conditions for staff and pool users

• Help combat climate change by cutting carbonemissions

• Help meet local and national sustainability targets

• Attract more customers by demonstrating a socialresponsibility for reducing carbon emissions.

In a large hotel, the poolalone can account for asmuch as 10% of totalenergy costs

Further information

Sports and leisure sector overview (CTV006)Hospitality sector overview (CT V013)Schools sector overview (CTV019)

Further and higher education sectoroverview (CTV020)


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03Swimming pools

Swimming pool water needs to be continually heated in order to overcome

the cooling effect of evaporation and maintain comfortable temperatures.It must also be continuously ltered and treated, so it is not surprising thatpools are signicant users of energy.

Energy consumption

Pool halls and changing areas are typically kept warmerthan other spaces as pool users are wet and wear lessclothing. Moreover, bathers consume large volumesof shower water which adds to the overall energyconsumption of pool facilities.

Using energy efciently can save up to 25% ofoverall operating costs of a typical swimming pool.Implementing good energy management techniquescan minimise consumption without lowering thestandard of service to users.

The major energy consumption areas in an indoorpool hall and their associated costs are shown inFigure 1 below.

In order to achieve the greatest savings potential, poolhall managers should know where the majority of theirenergy is being consumed and/or wasted. Typicalcommon wastage areas within the wet leisure sector are:

• Space heating and ventilation

• Water heating and treatment

• Lighting

• Motors and drives (particularly for pool pumpsand ltration equipment).

Fans and pumpsGeneral power

LightingSpace heating

Water HeatingFans and pumpsGeneral power

LightingSpace heating

Water Heating

Figure 1 Proportion of energy used in an indoor pool Figure 2 Cost of energy used in an indoor pool


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04 The Carbon Trust

In each of the key consumption areas, there are threemain opportunities to save energy:

Control – all energy-consuming equipment shouldbe controlled carefully to give the required conditionsand switched off when not required.

Maintenance – a number of energy efciency measurescan be carried out as part of routine maintenance forlittle or no extra cost.

Refurbishment – energy saving measures taken whenplanning major building refurbishment can beextremely cost-effective.

In most wet leisure facilities, energy is supplied in twoforms: fossil fuel (gas, oil, coal or LPG) and electricity.For the majority of sites, space heating and hot wateris supplied by fossil fuel. However, some facilities onlyhave access to electric ity or use it more extensively.Electricity is also used for lighting, electrical equipment,fans and pumps.

Reducing electricity consumption should take a highpriority in an energy efciency plan as it has higher costand carbon emissions per kWh used than most fossilfuels. Moreover, most elec tricity wastage is within thecontrol of end users and can be minimised through

good energy management and increased awareness.

Energy benchmarking

Benchmarking allows a pool owner to compare energyperformance with other similar pool buildings acrossthe UK and, over time, with their own previousperformance. Calculating a benchmark based on energyconsumption per unit of oor area of a pool hall allowsdirect comparison with other facilities, giving managersan idea of how energy efcient their pool is. The mostrecent benchmark gures for swimming pools werepublished in 2001 in the Carbon Trust publicationEnergy use in sports and recreation buildings (ECG078).Although these gures are a little dated, they can stillbe used as a rough guide to performance relative to

other organisations.

There are lots of opportunities for saving energy and,therefore, money and carbon emissions. Many of theserequire little or no cost, although others require someinvestment. The following section gives details ofopportunities relevant to all pools.

A helping hand online

Benchmarks and information on how to calculateyour energy use and CO 2 emissions can be foundonline at www.carbontrust.co.uk/energy

Further information

Fact sheetsUnderstanding your energy consumption (CTL001)Assessing the energy use in your building (CTL003)


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05Swimming pools

Pool halls – space heating and ventilation

Ventilating and heating pool halls can be rathercomplex and it is essential to manage these servicescorrectly. The control of evaporation from the wateris a function not normally encountered in standardheating, ventilation and air conditioning (HVAC)

systems, and can therefore be misunderstoodby designers and operators.

The ventilation system is normally the primary (or only)means of:

• Controlling the pool hall air quality, temperatureand humidity so as to reduce evaporation from thepool and prevent condensation (and, potentially,corrosion damage).

• Maintaining comfortable environmental conditionsfor different occupants.

•

Removing contaminants from the air.

Comfort requirementsMaintaining sa tisfactory environmental conditionsin the pool hall and all other areas of the building iscrucial to the comfort of bathers, lifeguards, staff andspectators. It is also essential if the pool is to operatesuccessfully over its working life.

In addition to the fact that pool users are wet andwearing less clothing, they will also experienceevaporation as they dry, which gives a cooling effect.As a result, higher than usual air temperatures needto be maintained. Evaporation also depends onthe relative humidity in the air, but bathers arerelatively tolerant of changes in humidity providedthat air movement is minimised, for instance,by avoiding draughts.

Heating and ventilation of the pool hall has to accountfor a wide range of factors such as the number ofbathers, water temperature, insulation of the pool halland integration with the building structure. Air andwater temperature should be set relative to each otherto optimise user comfort and minimise evaporationfrom the pool water. Above all, humidity and moisturecontent in the pool hall needs to be controlled toavoid condensation.

Space heating and ventilation accounts for a large proportion of energy use

in pool halls – which means that there are big opportunities to make savings.However, it is important to ensure that the primary functions of the heating,ventilation and air conditioning system are not compromised.

Top tip

If a swimming competition attracts manyspectators, it may be appropriate to reduce theair (and water) temperature to provide optimuminternal comfort conditions.


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06 The Carbon Trust

Air movement

A pool hall air circulation system needs to distributeair effectively so that:

• Comfortable temperatures are provided for occupants

• Air movement is controlled so it does not produceuncomfortable draughts

• Smells produced by water treatment are removed/ reduced

• Evaporation and condensation is minimised.

There are three locations within the pool hall wherethese issues should be addressed and each one is

examined in more detail below. These are: the poolsurface, the pool side and other areas, such as upperwalls and the ceiling void.

Pool surface

The key elements to be addressed at the pool surfaceare to remove contaminants if they could affect bathers,to provide bathers with oxygen for respiration and tocontrol evaporation.

• Remove contaminants – although sometimesunpleasant to smell, the odours caused by the water

treatment process are not usually dangerous andare generally accepted as part of the swimming poolenvironment. Instead of relying on ventilation toremove smells, a better approach is to control thewater treatment process itself. Contac t a watertreatment chemical supplier for more information.

• Respiration – bathers need to be able to breathecomfortably; however, as in other spaces, thisrequirement is met adequately by air diffusion withinthe pool hall. Coupled with the activity of bathers,this means that no deliberate effort has to be madeto deliver air to the bather at the pool surface.

• Evaporation control – air movement at the poolsurface encourages evaporation to occur. Therefore,it is better to avoid deliberate air movement suchas directing air onto the pool from jets built intothe ductwork if other comfort requirements canbe met without constantly refreshing the air at thepool surface. Angle jets towards the sides of thepool hall away from the surface of the water.

Pool side

The comfort of the bather (before entering and afterleaving the pool) and of the poolside staf f are the keyelements to be addressed at the pool side.

Most of the people who use the pool hall will be wet,so the poolside temperature should be adjustedaccordingly. This can be assisted, for example, byredirecting any grilles and jets near the pool side toavoid any direct air ow from the ventilation system.Staff should also be discouraged from opening doorsor windows, which creates draughts.

Discourage poolside staff from opening emergencyescape doors for their own personal comfort. Iflocalised cooling is required, this can be providedby increased air movement such as through simple

overhead fans. Use controls to avoid increasing airmovement at the pool surface or around wet bathers.

Temperatures elsewhere in the swimming poolbuilding, such as café areas, the foyer, administrationofces and plant rooms should be appropriate forthe activities taking place.


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07Swimming pools

Comfort for spectators can be improved by havinga similar arrangement to direct drier incoming air over

them. It may also be appropriate to blow drier air intoceiling voids to ensure that condensation does notoccur on hidden parts of the structure.

These approaches that separate air ow within thespace have clear advantages over a traditional systemin which all the air ows are mixed, demanding thatall air in the pool hall be brought down to the limitingmoisture content demanded for structural protec tion.

Other areas in the pool building

The key elements to be addressed in other areas ofthe pool hall are protecting the pool hall structure fromcondensation and providing comfort to non-swimmers.

One solution to both problems is to provide separateair ows for the pool and other areas to minimisemixing between areas. In a new pool building, the airow could be directed upwards from a slot at the footof the walls in ‘laminar ow’, so that it mixes as littleas possible with the bulk of air in the hall. For existingpool buildings, inlet grilles and jets can be repositionedso that drier air entering the pool hall can be pointedtowards the sides of the building rather than down

on to the pool.

Outside air normally has much less moisture in it thanpool hall air as it has a lower temperature. Mixing outsideair with pool hall air can reduce overall humidity


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08 The Carbon Trust

Controlling humidity

Regardless of whether air ow patterns have beenarranged to reduce evaporation, it is important tocontrol moisture condensing on cold surfaces bylimiting humidity. The alternative methods ofdehumidication are :

• To dilute the air close to surfaces which are prone tocondensation with dry air from outside the building

• To directly dehumidify the air.

DilutionOutside air normally has much less mois ture in

it than pool hall air as it has a lower temperature.Mixing outside air with pool hall air can reduce overallhumidity. The outside air has to be heated up to thepool hall temperature to make it comfortable forbathers, which uses energy. To make room for thisincoming air, the air already in the pool hall must beextracted. Pool hall air has a high temperature and alsocontains the latent heat of the moisture evaporatedfrom the pool so it can be wasteful. However, someof this energy can be captured and returned to thepool hall, thus achieving savings (see the heat recoverysection on page 9).

The volume of incoming air used to dilute the pool hallair can be reduced to the minimum consistent withavoiding condensation by using variable speed fans.

Direct dehumidicationThis approach strips moisture out of the air withinthe pool hall system, rather than simply dilutingit with outside air. In this way, the heat requiredto maintain conditions in the pool hall is reducedto what is needed to replace direct losses throughthe building structure and the heat needed to warmfresh air needed for respiration.

The two main ways to achieve this are through theuse of a dehumidifying heat pump or a desiccant wheel.The cost effectiveness of both options needs to beevaluated carefully in life cycle terms. In either casethey need to be able to cope with the corrosive air theyhave to handle, which can considerably reduce plantlifespan if not addressed. In addition, both options needto be controlled to achieve the correct function, and thecontrol regime must be understood by plant operatorsas direct dehumidication is a radically different

approach from that traditionally employed.

Controlling condensation

As air temperature increases, it can hold moremoisture in the form of invisible water vapour.Pool hall temperatures can hold more moisturethan air at ordinary room temperatures, causingcondensation to occur as the warmer, moist airmoves over cooler surfaces.

Condensation is rarely an issue in most buildingsand even then is predominantly a cosmetic problemwhich can be caught before it does too much damage.Swimming pools, however, have additionalcomplications. For example, the condensate maycontain aggressive chemicals from the water treatmentprocess or there may be a suspended ceiling concealingthe structure, so that damage may occur unnoticed.

There are two ways to avoid this happening:

• Insulate the cold surface on which condensationmight occur so that the surface temperature is alwaysabove the dew point. The ‘dew point’ refers to thetemperature at which the air is saturated with watervapour, corresponding to 100% relative humidity –as the air temperature falls towards dew point thisis when condensation occurs. The insulation shouldpreferably be located outside the s tructure so thatthe whole of it remains warm.

• Reduce the moisture in the air so that the relativehumidity is less than 100% when it contacts thecold surface.

Safety rst

Condensation-related damage can occur out ofsight and pool roofs have been known to collapsedue to undetected corrosion. It is important tocarry out regular preventive checks and alwaysconsult a qualied specialist where necessary.


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09Swimming pools

Desiccant wheelsA desiccant wheel passes air from the pool hallthrough a disc comprising a hygroscopic honeycombmatrix which absorbs the moisture. Thus the air isdehumidied and returned to the pool hall withoutmuch change in temperature. The disc rotates and aseparate hot (usually gas-red) stream of air is passedthrough it to remove the moisture and recharge thewheel ready for its next pass through the pool hallextract air-stream. The hot air is discharged fromthe building with the water vapour.

A plate heat exchanger or run-around coils can be usedto recover some of this waste heat, to preheat incoming

fresh air to the pool hall. For further information anddetails of suppliers, contact the Carbon Trust on0800 085 2005 .

If the pool already has a desiccant wheeldehumidication system installed, make sure that:

• The controls are set up as recommended by theoriginal installer to reduce the humidity only to thatlevel required to avoid condensation on the structure

• The hygroscopic material is still actively absorbingmoisture

• Heating of the hygroscopic material is limitedto the amount needed to regenerate it, in orderto avoid waste.

Although humidication control (using dehumidiersfor example) can control pool hall humidity conditions,this does not replace the need for adequate ventilationto control air quality.

Dehumidifying heat pumpsA dehumidifying heat pump consists of an elec tricallydriven heat pump where air from the pool hall passesover the evaporator or cold coil. Moisture condensesout of the air at the same time as it is cooled and thewater is run to drains (or can be stored for cleaningor toilet ushing). The air is then reheated by passingit over the condenser or hot coil of the heat pump.Thus the air is dehumidied and returned to the poolhall at the right comfort temperature.

The considerable latent heat in the air beingdehumidied produces a surplus that can be used toheat the pool. This can make up for the cooling effect

caused by surface water evaporation from the pool inordinary use. The recycling of otherwise wasted energyfrom the latent heat of the air used to heat the poolwater makes this system highly energy efcient.

If the pool already has a heat pump dehumidicationsystem installed, make sure that:

• The controls are set up as recommended by theoriginal installer

• Recovered heat is returned to both pool hall airand pool water

• The dehumidied air returns to the pool hall andis not exhausted to outside

• Cooling coils are clear from blockages or corrosionso that air ow through them is not impeded.


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10 The Carbon Trust

Ventilation rates and controls

The ideal ventilation rate for a pool hall varies inaccordance with a number of factors such as thenumber of bathers, evaporation rate and water qualityat any given time. A recommended guideline gureof 10 litres of ventilation air per second, per squaremetre of total pool hall area (water area plus all wetsurrounds) is acceptable for a wide range of poolcomplexes. This normally results in an overall totalof approximately 4–6 air changes per hour dependingon the height of the pool hall.

Ideally, the speed of the ventilation fans should becontrolled using variable speed drives (VSDs) linked toa dew point sensor. This optimises the speed of the fansto keep the moisture content of the air in the pool halljust above the dew point at which condensation occurs.Further information can be found in the Carbon Trust’sfactsheet Variable speed drives technology guide(CTG006).

Place the sensor so as to avoid condensation onthe worst ‘cold bridge’ in the structure. A cold bridge

is formed where the thermal insulation barrier isbreached, leaving a bridge that short-circuits thethermal insulation and results in a colder surfacethan the surrounding area. In a pool building, thiswill usually be a window frame or structural s teel.

As an alternative to dew point sensors, a relativehumidity sensor can be employed to control the airsupply. It should be reset depending on the outsidetemperature. When the outside temperature is belowfreezing, for example, the relative humidity required toavoid internal condensation will be lower than in milderweather or summer. Note that these sensors requirefrequent recalibration.

Did you know?

Extensive water features cause more evaporationso pools with these may have to have 8–10 airchanges per hour as a result.


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11Swimming pools

Heat recovery

Heating the supply air is generally one of the majorconsumption areas for a pool building. Providinga simple heat exchange device, such as a plate heatexchanger or run-around coils, can optimise energyefciency by reclaiming large amounts of lost energyfrom the exhaust air.

Fit heat exchangers with a bypass in the ductwork foroccasions when heat recovery is not required. However,make periodic checks to ensure that they are notpermanently bypassed and normally operate in the‘heat recovery’ position.

Moist extracted air

Input air

A

GC

F

B D

J

E

H

I

H e a

t R e c o v e r y

A Air intake

B Air lter

C Heat recovery device transferringheat energy from the air beingremoved from the building to thesupply air entering the building

D Centrifugal fan

E Air heater

F Extract fan

G Air extract

H Pool water calorier

I Boiler system

J Heating water pump

Hot water ow

Cold water ow

Figure 3 Simplied diagram of a pool hall air handling system

Plate heat exchangers

Plate heat exchangers consist of glass, metal or plasticplates arranged in a stack with the exhaust air andincoming air owing in the adjacent channels. Heattransfers from the outgoing air from the pool hall(which is warm and moist) through the plates tothe cold incoming air. They are cheap and free frommechanical problems, although a limit on theirapplication is that the incoming and outgoing airducts must be adjacent to each other.

If grease and grime are allowed to build up on theplates this will lead to a subs tantial reduction intheir effectiveness, so the heat exchanger should

be maintained in accordance with manufacturers’specications. If the plates are made of metal,chlorinated air can attack them. Inspec t for signsof corrosion at least once a year.


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Run-around coils

In this device, two pipe coils are connected by a pumpedwater circuit. One coil is placed in the extract duct to pickup waste heat, the other in the supply duct to pre-heatincoming air. The advantage of this system is that thetwo ducts do not have to be adjacent and so it can beretrotted to an existing ductwork installation. If heatrecovery is not required, the pump can be turned off.

The disadvantage of this system is that it is not aseffective as other heat recovery methods owing to heatlosses from pipework between the two coils and theenergy used to drive the pump.

Rotary heat exchangers

Rotary heat exchangers or ‘thermal wheels’ arehoneycomb meshes that slowly rotate and alternatelypass through the outgoing warm air stream (where theyabsorb heat) and then through the incoming cool air(where they release heat). They can save considerableenergy, although their application again depends on theincoming and outgoing air ducts being adjacent to eachother. The honeycomb mesh has to be chosen carefullyto be compatible with the moist, chemically aggressivecondition of the pool hall air extract.

Rotary heat exchangers have par ticular maintenancerequirements associated wi th their drive and seal

mechanisms yet are very ef fective and popular. Wherethe wheel is easily visible, a daily check should bemade to conrm that it is rotating at the manufacturer’srecommended rate. In addition, check every sixmonths that:

• The wheel is rotating at the correct speed

• The bearings are lubricated

• The seals are in good condition

• There are no signs of corrosion

• The honeycomb mesh is clean.

It is important that rotary heat exchangers areinspected. If they s top rotating and become blocked,ventilation will be signicantly reduced which couldlead to condensation in the building structure withserious consequences.

Exhaust airWarmed return airfrom pool hall

Cool outside air Warmedsupply air

Note

All heat recovery devices should be carefullyevaluated over the projected life cycle of thebuilding services installa tion. They may saveheat energy (usually fossil fuel) but increaseelectricity usage in the fan motor, which ismore carbon intensive.


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13Swimming pools

Dampers are used to control whether air is routedthrough one duct or another, the proportion of fresh

to recirculated air, and the emergency cut off to stopair movement in case of re. Checks should beconducted to ensure:

• They are operating correctly in accordance with thecontrol strategy (at some pools they have been foundto be operating in the opposite direction to thatintended)

• They are lubricated regularly to avoid being jammedin one position.

Correct controlMake sure appropriate time and temperature controlregimes are in operation and consider interlockedcontrols so that heating and cooling cannot operateat the same time. It is essential to understand theconsequences before changing any temperatureor humidity settings in order to avoid damaging thebuilding fabric. Always consult a qualied technician.

Further information can be found in the Carbon Trust’soverview of Heating, ventilation and air conditioning(CTV003) and Heating control (CTG002).

Other considerations

Choice of heat sourceWhen undertaking refurbishment, specify highefciency condensing boilers or consider installingcombined heat and power (CHP). This is coveredmore on page 18.

Ductwork and dampersDuctwork should be checked annually to ensure that:

• It is internally clean and free of leaks, especiallyat duct junctions

• Insulation is sound

• Flexible connections between ducts and fans or otherplant are not taut or split. If dust is found, this mayindicate leaks or loose panels elsewhere, or failureof lters, and should be investigated.

It is essential to either remove or protect any sensorswhen ductwork is cleaned.

Case study:Luxury hotel

A large luxury hotel with a heated indoor swimming

pool installed a CHP system which interfaced withother hotel services, including the Building EnergyManagement System (BEMS). In its rst 11 monthsof operation, the unit generated 2.0 million kWh ofelectricity and 2.8 million kWh of heat, providingannual savings in excess of £50,000 and reducingcarbon dioxide emissions by 1,000 tonnes per year.


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14 The Carbon Trust

Pool water – heating and treatmentWater heating is essential for efcient operation of the pool, showers and

other facilities in a pool building. Since the pool water itself is recirculatedcontinuously, it needs to be disinfected. Although the chemical treatmentof pool water is not considered in this guide, its quality and the associatedprocesses do have energy consumption implications.

For example:

• Micro-organisms multiply faster – up to twice as fastfor a 10°C rise meaning that lters are increasingly

likely to become colonised.• Bathers get hotter, limiting serious swimming and

increasing sweat and grease in the water.

• Energy costs and carbon emissions, direct andindirect, are higher regardless of the efciencyor conservation methods used.

• Air temperatures – being linked to water temperatures– also rise, making the atmosphere less comfortablefor staff and spectators.

• There is more moisture in the pool atmosphere, even

when relative humidity is controlled at the same level.This increases the risk of condensation and possiblycorrosion and deterioration of the building fabric,structure and equipment.

• Dissolved gases become less soluble, leading toincreased chemical odours and a rise in the pH valueof the treated water as carbon dioxide escapes.

Pool water heatingThe heating of pool water is a relatively simpleoperation which is generally carried out by the

introduction of a heat exchanger to transfer heatfrom the primary heating system, sometimes viaheat recovery systems, to the pool water. The heateris typically sized, based on raising the pool watertemperature by 0.5°C per hour (to adjust temperatureand ‘make good’ heat lost by, for example, evaporationand backwashing).

If a pool is being heated from cold, the rate must be nomore than 0.25°C per hour, otherwise the expansion ofmaterials may cause problems to the pool structure orlining. For new pools, the precise rate of temperaturerise should be predetermined by its designers. Correctlyspecied and operated controls are the key to efcientpool heating.

Ideal water and air temperaturesThere has been a consistent trend towards higher watertemperatures in recent years, encouraged by thesubstantial growth in leisure pools and special eventssuch as swimming sessions for young children. Currently,main pool temperatures tend to be set around 29–30°C.This increase has been in response to customer feedback,particularly in leisure pools where there is less actual

swimming activity.

Some pools do need to be this warm, for instance whencatering for parents and toddlers or for rehabilitationpurposes. However, operators tempted to increasetemperatures should bear in mind that this createsa number of problems.


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15Swimming pools

Evaporation

There is a direct link between the energy consumptionof ventilation systems and evaporation of water vapourfrom the pool. The amount of heat energy in the poolwhich is lost to evaporation depends on the airconditions immediately above the pool. This energy,together with a small amount of heat loss throughconduction and radiation, represents a major part ofthe energy exchange from the pool to the pool hall air.Controlling this is therefore key to saving energy.

The rate of evaporation from the pool depends on thedifference between the moisture content of the air atthe water surface, the moisture in the air just abovethe surface and also the air velocity. If the air above thesurface can be as stationary as possible, it will becomesaturated and evaporation will be minimised. If the airmoves, however, drier air will enter the space immediatelyabove the pool, the moisture difference will increase andevaporation will increase. Thus the key to reducingevaporation is to minimise the air movement immediatelyabove the pool.

This will inevitably conict with bathing activity in thearea, so some evaporation will always take place whenthe pool is occupied. This is why the pool must be

continually heated even after it has been warmed up,to maintain bather comfort.

Evaporation is also increased if the water is sprayedor agitated by water features such as wave machinesor umes, because the surface area is increased. Toprevent wastage, limit the use of water features, ratherthan operating them continuously. As well as reducingevaporation, this will also reduce pumping energy andprovide a more varied swimming environment.

When the pool is unoccupied it may still be necessaryto run the pool ventilation sys tem to maintain

environmental conditions within the pool hallto prevent condensation.

With an increasingly wide variety of pool activitiestaking place, and with operators attempting to introduce

more exibility into pool operation programming, it isdifcult to select a single appropriate or optimumoperating temperature for any particular pool. The largevolumes of water involved make it impossible to varywater temperatures to a great extent in any one area.This means that selection and accurate control of theoptimum water temperature for each pool is essential.

The air temperature in the pool hall should be similarto the water temperature – ideally 1 oC above. This helpsreduce evaporation and convection of heat at the poolsurface. It also makes it more comfortable for bathers

leaving the pool. Air temperatures of 30o

C or moreshould generally be avoided.

Recommended water temperatures

27°C – competitive swimming and diving, training,tness swimming

28°C – recreational use, conventional main poolsand adult teaching

29°C – children’s teaching, leisure pools

30°C – babies, young children, disabled

Further information

You could also consider alternative heat sourcessuch as a biomass boiler.

See our case study on Mid Argyll SwimmingPool (CTS043).


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16 The Carbon Trust

A wide variety of covers is available, includingmotorised models which can be withdrawn to the side

or bottom of the pool to minimise the labour input atchangeover. When selecting a suitable cover, considerthe following factors:

• Resistance to water treatment chemicals and UV light

• Strong and durable materials and construction

• Good insulation properties and suitable tting

• Storage ability and ease of use

• Safety requirements for staff and pool users.

Pool covers also provide additional benets in terms of

building maintenance. A reduction in pool hall humidityand condensation can help to prolong the life of thestructure and reduce building maintenance.

It is important to train staff to use covers properly –and regularly – in order to achieve maximum energysavings. Ensure staff and lifeguards have adequatesafety training to ensure that they know what to doshould anybody become trapped underneath a cover.

Pool covers

The use of pool covers out of hours reduces theevaporation rate from the pool surface and can savesignicant amounts of energy in swimming pools.

• The lower evaporation rate reduces the energyneeded to keep the pool water heated to the requiredtemperature and the resulting reduction in energy useis signicant.

• The reduced evaporation lessens the need for highventilation rates and air heating in the pool hall canbe reduced or shut off. This allows the air circulationsystem to be shut off, or turned down to a very low

rate, when the covers are on.In practice, some water may get on to the top of the poolcover and there may be some evaporation at the sideswhere the cover does not quite t. There may also besome residual moisture in the air after the cover has beendeployed so it may still be necessary to run the ventilationsystem at a low setting. Nevertheless, an effective poolcover will reduce the need for dehumidication out ofhours and therefore substantially reduce energyconsumption. Even where covers do not match the shapeof a free form pool, they are still worthwhile: evaporationis still reduced in proportion to the area covered andhence yields energy and cost savings.

Did you know?

Insulated pool covers are one of the most costeffective investments available to swimming poolmanagers. Typical savings can be 10–30% of totalpool energy use with a payback period of 18months to three years.

An effective pool cover will reduce the needfor dehumidication out of hours and therefore

substantially reduce energy consumption


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17Swimming pools

Showers

Pollution of the pool water, for example through sweat,urine or cosmetics is a big issue for pool operators.A build up of pollution can be reduced by encouragingbathers to shower and use the toilet before entering thepool. While this may increase shower water heating, itreduces the need for disinfection and lter backwashingand may improve the appearance of the pool. Moreover,there are ways to lessen the effect of the ex tra hotwater demand. For example, reduce the quantity usedby bathers by introducing push button controls insteadof conventional taps, so that they are not left running.

In some circumstances, where sewers are unable totake large sudden outows of water, for backwashing,say, the centre must store the water and dischargeit at a slow rate. In this case, energy could be savedby applying water to water heat recovery to preheatincoming water which enters the building atapproximately the same rate as this discharge. Anyheat exchangers used in this way should be capableof being dismantled to allow periodic cleaning.

During refurbishment projects, install a dedicated hotwater heater for showers rather than storage calorierswhich are prone to energy losses. Make sure that the

insulation is intact and at the required thickness in hotwater storage systems.

Explore solar water heating potential

Solar water heating can be very effective for showersand for heating pool water. Modern systems arerelatively easy to connect to a conventional heatingsystem. Unglazed solar collectors perform well insummer and are generally the cheapest to buy andinstall. Glazed collectors provide more energy in springand autumn and can give a substantial contribution topool heating throughout the year, with the remainderprovided by a conventional heating system.

Pool water treatment

Although the chemical treatment involved in this processis outside the scope of this guide, it should be noted thatmost systems rely on a residual chemical level to dealwith pollution input as the water circulates through thepool. There will always be some air contamination fromthe volatile products of the water treatment process,and hence a need for ventilation to dilute the smell.

Most treatment systems incur a build-up of dissolvedsolids which must be reduced periodically by dilution andoften by backwashing. Backwashing refers to a processwhere the ow of the pool water through the lter isreversed to ush out the accumulated debris, such as hair,in the lter.

The water used in dilution must be reheated, as must thefresh water used to replace that used to backwash thelters. This will have to be heated up from the mainssupply to the comfort temperature of the pool, requiringenergy input from the boiler or other heat generator.

It is important to maintain an appropriate intervalbetween consecutive backwashes of a pool lter toreduce energy and water consumption. Backwashingis very costly in both water and energy terms so anyreductions in this area will lead to signicant cost savings.

Although energy can be saved by minimising the waterquantity going to waste, take special care to avoidcompromising water quality and safety. The intervalbetween backwashes will depend on the type of pooland the degree of usage. Some pools will remain cleanand safe with regular cyclic backwashes but somemanufacturers advise that the pressure drop across alter is a better indicator of when a backwash is required.Always consult the manufacturer of the pool equipmentwhen considering changing the maintenance regime.Further information can be found in HSE guidelines at

www.hse.gov.ukIn swimming pools, it is important to ensure full mixingof the water in the pool after ltration/disinfection, so thatthere are no pockets of poor quality water which are notrefreshed. The turbulence near inlets to achieve this maygive the appearance of unnecessarily high pressures.If this is the case, consult the pool water designer onwhether the pressures at the pump are really necessaryto maintain adequate mixing. If pressure can be reduced(through changing impellors or by reducing motor speed)energy can be saved. Note that high pressure may alsobe necessary to operate lters and lter cleaning.


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Effective maintenance forheating plantHave boilers serviced regularly by a reputable rm.Gas-red boilers, which are most common in leisurefacilities, should be serviced once a year; oil boilerstwice a year. A regularly serviced boiler can saveas much as 10% on annual heating costs.

Insulate boilers, hot water tanks, pipes and valves toprevent heat escaping. Payback can usually be expectedwithin a few months of installation, with additionalsavings in subsequent years.

As well as providing heat for the pool hall, boilers alsoprovide hot water which is used in changing rooms andcatering facilities, so it is particularly important to keepthem in good condition and as efcient as possible.

The Carbon Trust has further advice on energy savingwith boilers, including a Low temperature hot waterboilers technology overview (CTV008).

Combined heat and power

Combined heat and power (CHP) is the on-sitegeneration of electricity and the utilisation of the heatthat is a by-product of the generation process. It savesenergy and reduces carbon emissions by making theengine’s heat, which would normally be wasted,available as hot water. It could therefore substantiallyreduce a swimming pool’s electricity requirement fromthe mains supply. It will increase gas use to some extentbecause CHP produces hot water with less efciencythan a boiler. For larger swimming pools, CHP can of feran economical method of providing heat and powerwhich is less environmentally harmful than

conventional methods.To gain maximum benet from CHP, the system needsbe in operation for as many hours of the year aspossible. With year-round requirements for electricityand hot water, swimming pools can be well suitedto using CHP although the economics depend onthe relative prices of purchased gas and displacedelectricity. Use proprietary CHP sizing softwareto nd out whether it is worthwhile. An expert shouldthoroughly investigate the site and carry out a completenancial and technical appraisal. For more informationcall the Carbon Trust on 0800 085 2005 .

Did you know?

In an appropriate application, CHP can reduceenergy bills by around 20–30%, provided the unit isdesigned to meet the building’s seasonal demandsfor electricity and heating. Even better, goodquality CHP qualies for Enhanced CapitalAllowances and the fuel input is exempt from theclimate change levy (CCL). Contact the CarbonTrust for more information.

Top tip

Ensure pipework is checked regularly for leaks.A leaky pipe costs money for the water and heatbeing wasted. To reduce energy losses, also makesure that pipework is properly insulated. Regularlycheck the condition of insulation and replace if itis damp or worn.


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19Swimming pools

Choose efcient replacementsWhen a lamp fails, it presents a useful opportunityto substitute a more efcient lamp type. Lightingtechnology progresses quickly and alternatives shouldbe investigated, especially when refurbishment is beingundertaken. Consider the substitutes outlined belowand avoid automatically replacing like with like.

As well as selecting energy efcient light sources, thereare a number of important design issues to considerwhen lighting a swimming pool. These include:

• Minimising reected glare from light ttings off thepool surface

• Ease of maintenance when replacing bulbs andcleaning ttings

• Sourcing light ttings that resist corrosion

• The colour performance of lamps.

Some key efciency measures are outlined below. Moredetailed information relating to lighting and controls isavailable in the Lighting technology overview (CTV021)available from the Carbon Trust.

LightingLighting accounts for up to 16% of the total energy costs in an indoor pool

hall or wet leisure facility. There are many simple and inexpensive ways toreduce the energy consumption and costs associated with lighting withoutcompromising internal comfort levels.

Replace standard lamps

Replace standard incandescent tungstenlament lamps with compact uorescentlamps (CFLs) that last up to eight timeslonger than their tungsten counterparts,which means less time spent replacingthem. They have a similar light outputto tungsten bulbs and use only 20–25%

of the energy.

Replace T12 tubes with T8 andT5 tubes

All 38mm diameter (T12) uorescenttubes can be replaced with slimmer,26mm diameter (T8) tubes. Whenreplacing luminaires – the light tting– consider those that will take the moreefcient T5 uorescent tubes. Alwaysspecify tubes with a triphosphor coating– this will be stated on the packaging.

Consider long-life lamps

If lights are placed in difcult areas toreach, for example directly over the centreof the pool, choose long-life lamps suchas metal halides and sodium lamps. Metalhalide lamps can be used in the pool areaand in other areas where the colourrendering properties of high pressuresodium lamps are not sufcient.

Tax incentives

Enhanced Capital Allowances (ECAs) enablebusinesses to buy energy efcient equipmentusing a 100% rate of tax allowance in the yearof purchase. Businesses can c laim this allowanceon the investment value of energy efcient cateringequipment if it is on the Energy Technology List.The procedure for claiming an ECA is the sameas for any other capital allowance. For furtherinformation, please visit ww w.eca.gov.uk or call theCarbon Trust Customer Centre on 0800 085 2005 .

Further information

Lighting technology overview (CTV021).www.carbontrust.co.uk/lighting

For help implementing energy efcient lighting, seewww.carbontrust.co.uk/lightingimplementation


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20 The Carbon Trust

Daylighting

Most swimming pools have good levels of naturaldaylighting from windows or roof lights. In many cases,there will be sufcient daylight to allow some articiallighting to be switched off during the day. Appoint astaff member to ensure this occurs and, if necessary,change the switching arrangement so that selectedlights can be turned off separately using appropriatedaylighting controls.

Cleaning windows and skylights regularly will allowmaximum daylight to enter the pool hall and signicantlyreduce the need for electric lighting. Clean glass isparticularly important for urban swimming pools wherehigh levels of pollution can cause a lm of dirt to settleon windows and particularly roof lights.

Where daylight is used in the pool hall, ensure thatlifeguards are positioned so that their view underthe water is not obscured by reec tions from brightwindows or interior light sources.

Consult a lighting specialist

For new build or refurbishment projects, consult alighting designer or dedicated lighting specialist. In mostcases, a qualied designer will be able to identify savingswhilst maximising the quality and aesthetics of the nalresult. When commissioning a designer, it is importantto work through the actual requirements of the nisheddesign and ask them to specically consider:

• The safety and comfort of staff and pool users

• The pool hall architecture and layout of the building

• How the design can help to achieve the lightingrequirements, including any specialist needs such

as lighting for swimming or diving competitions(see below)

• How the use of daylight can be maximised includingutilising suitable controls

• The costs of installing and operating the systemincluding maintenance costs and ease of access

• The most energy efcient design possible – make surethat low energy options are specied from the outset.

Competition poolsThe Fédération Internationale de Natation (FINA)species particular rules and regulations forpools offering competitive and training facilities.For example, provision of a higher lighting levelthan that used for recreational swimming isrequired for competitive events. Moreover,if a pool is to be used for competitions under FINArules, consideration should be given to separateswitching regimes. For more information,visit www.na.org


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21Swimming pools

High efciency motorsHigh efciency motors (HEMs) rarely cost more, but usebetween 3–5% less energy. They also qualify for 100%tax relief under the Enhanced Capital Allowance scheme.Visit www.eca.gov.uk for more details. HEMs make agood replacement option for an existing failed motor.

Variable speed drivesIn applications where a motor is required to servea variety of load conditions, such as varying supplyand extract volumes to remove moisture in a poolhall, consider installing a variable speed drive. Thesedevices can alter the speed of a motor, enabling themotor to operate efciently in a range of differentconditions.

Switch-off policyThere are many motors in the average pool hall andthey are usually hidden within machinery. So motorstend to be ignored or left running even when they aredoing no useful work. Develop procedures to ensurethat ‘idle’ motors and pumps are switched off when notin operation. This may involve devising a switch-offprocedure and placing instructions in visible locationsaround the building. The procedure should also takeinto account the maximum number of ‘star ts’ allowedfor each motor.

Clean componentsMotors should be kept clean and free of dust and othercontaminants. Pay particular attention to motorssituated in the corrosive atmosphere of pool water

treatment areas or those in dirty or dusty environments.Consider putting a preventive maintenance plan inaction to address this issue.

Correct motor sizing – over-sizing leadsto inefciencyA smaller motor running at a higher loading will bemore efcient than a larger, partially loaded motorand it will consume less energy. For example, swappinga single 10kW motor running at 25% loading for a2.5kW motor running at full load could save around£70 per year.

Motors and pumpsMotors, fans and pumps are used widely throughout the pool building for

water treatment and ventilation systems. Collectively, they are responsiblefor more than 25% of the energy costs in swimming pools so making motorsand pumps more efcient will yield signicant savings.

Did you know?

The cost of buying an electric motor can bedeceptive. In just a single year, the cost of theenergy required to run a motor can be up to 10times its purchase cost.

Further information

For more detailed information on energy savings

and motors, see the Carbon Trust’s Motorsand drives technology overview (CTV016) .


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Action checklistExisting systems Complete? Action/Comment

Ensure air temperature is set at 1 oC above water temperature to avoidconvection air movement

Control ventilation rates with a dew point sensor to the minimumrate consistent with avoiding condensation

If existing control is by humidistat, reset each season accordingto the outside temperature

If ventilation volume is set at ‘full’ or controlled manually or by timer,investigate how to link this with humidity levels as an alternative option

Reposition supply air outlets so that drier supply air entering the pool hallis pointed towards the building structure rather than down on to the surface

of the pool waterKeep doors closed between areas with different temperatures and humidity

Provide localised cooling for staff using overhead fans and discouragestaff from opening doors and windows if they are hot

Conduct regular pool backwashing and clean the pool lters to maintaingood quality clean water

Benchmark separately for fossil fuels and electricity to show potentialfor savings

Inspect system components such as fans, coils and pumps for corrosionand clean or replace if necessary

Minimise the frequency of backwashing consistent with achievingthe required minimum standard of water quality

Provide heating, lighting and hot water only to occupied areas

Inspect heat recovery devices and air lters once a month and cleanor replace if necessary

Walk around the premises at different times of the day and duringdifferent seasons to see how energy is being used. Develop an actionplan for making savings

Refurbishment and capital expenditure

Fit pool covers to minimise evaporation and ensure staff are trained

to use them properlyConsider tting variable speed drives on pumps and fans

Explore solar water heating potential

Replace ageing conventional boilers with high efciency condensing boilers

Consider combined heat and power; evaluate the economics includingmaintenance and plant replacement costs

Consider ventilation heat recovery and waste water heat recovery

Evaluate options for using heat pumps for dehumidication and utilisingthe recovered energy for pool heating

Investigate installing additional insulation and consider insulatingany existing cold bridges


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23Swimming pools

Next steps

Step 4. Seek specialist helpIt may be possible to implement some energy savingmeasures in-house but others may require specialisthelp. Discuss the more complex or expensive optionswith a qualied technician.

Step 5. Make the changes and measurethe savingsImplement your energy saving actions and measureagainst original consumption gures. This willassist future management decisions regarding yourenergy priorities.

Step 6. Continue managing energy efciencyEnforce policies, systems and procedures to ensureyour centre operates efciently and that savings aremaintained in the future.

Step 1. Understand your energy useLook around your pool hall and identify the major areasof energy consumption. Devise a control strategy andensure it is fully understood and implemented – thisis particularly important as many systems are oftencomplex and energy saving features are overriddendue to a lack of understanding.

Check the condition and operation of equipment andmonitor the power consumption over one week toobtain a base gure against which energyimprovements can be measured.

Step 2. Identify opportunitiesCompile an energy checklist. Walk round the buildingand complete the checklist at different times of day(including after hours) to identify where energy savingscan be made. An example checklist can be found earlierin this document and further ideas are available inAssessing the energy use in your building (CTL003),available from the Carbon Trust.

Step 3. Prioritise your actionsDraw up an action plan detailing a schedule ofimprovements that need to be made and when,along with who will be responsible for them.

Further information

HSG179: Managing health and safety in swimmingpools: available at www.hsebooks.com

CIBSE Guide F – Energy efciency in buildings:available at www.cibse.org

CIBSE Guide G – Public health engineering:available at www.cibse.org

Fédération Internationale de Natation (FINA)www.na.org

Start with the following easy low and no-cost options to help save money

and improve the energy performance of your pool hall.


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Glossary

Laminar ow

The smooth, non-turbulent ow of air or liquid.

Latent heat

The energy that is released or absorbed as heat bya substance as it changes s tate such as from a solidto a liquid.

Relative humidity

A term used to describe the amount of water vapour

that exists in a gaseous mixture of air and water,expressed as a percentage.

Relative humidity sensor

Measures relative humidity in the air and canbe used to alter ventilation rates in a pool hallto avoid condensation.

Thermal bridging

The part of the building fabric where heat is transferredat a much higher rate than the surrounding area.

Variable speed drive

An electronic device that controls the electrical supplyto a motor, enabling it to run at different speeds.

Zoning

Allows a building to be separated into individual areasbased on different requirements. Each zone may haveseparate time and temperature controls, allowingconditions in each area to be provided with heatingor cooling appropriate to its individual needs and thus

achieving energy savings.

Air handlers

The portion of heating and cooling systems that forceair through the ductwork of a building. Air handlersusually consist of a sheet metal box housing fans andother equipment such as heating and cooling coils.

Calorier

An apparatus used for the transfer of heat to waterin a vessel by indirect means, the source of heat beingcontained within a pipe or coil immersed in the water.

Commissioning

The process of testing, checking or calibrating thefunction of any building services component.

Dew point

The temperature to which the air must be cooled atconstant pressure in order for it become saturatedso that the relative humidity becomes 100%.

Dew point sensor

Measures relative humidity and identies the dewpoint in a body of air.

Ductwork

Distributes the air from air handlers to conditionedspaces. In many buildings, it is hidden behindsuspended ceilings and within walls.

Hygroscopic

A material that takes up moisture from the air.

Interlocking controls

Controls that prevent two or more systems operatingat the same time.


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The Carbon Trust provides a range of tools, services and information to help you implementenergy and carbon saving measures, no matter what your level of experience.

Carbon Footprint Calculator – Our online calculator will help you calculate yourorganisation’s carbon emissions.

www.carbontrust.co.uk/carboncalculator

Interest Free Loans – Energy Efciency Loans from the Carbon Trust are a costeffective way to replace or upgrade your existing equipment with a more energy efcientversion. See if you qualify.

www.carbontrust.co.uk/loans

Carbon Surveys – We provide free surveys to organisations with annual energy billsof more than £50,000. Our carbon experts will visit your premises to identify energy savingopportunities and offer practical advice on how to achieve them.

www.carbontrust.co.uk/surveys

Action Plans – Create ac tion plans to implement carbon and energy saving measures.

www.carbontrust.co.uk/apt

Case Studies – Our case studies show that it ’s often easier and less expensive than youmight think to bring about real change.

www.carbontrust.co.uk/casestudies

Events and Workshops – The Carbon Trust offers a variety of events and workshopsranging from introductions to our services, to technical energy efciency training, most ofwhich are free.

www.carbontrust.co.uk/events

Publications – We have a library of free publications detailing energy saving techniquesfor a range of sec tors and technologies.

www.carbontrust.co.uk/publications

Need further help? Call our Customer Centre on 0800 085 2005 Our Customer Centre provides free advice on what your organisation can do to save

energy and save money. Our team handles questions ranging from straightforwardrequests for information, to in-depth technical queries about particular technologies.

Go online to get more


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The Carbon Trust was set up by Government in 2001 as an

independent company.

Our mission is to accelerate the move to a low carbon economyby working with organisations to reduce carbon emissions anddevelop commercial low carbon technologies.

We do this through ve complementary business areas:

Insights – explains the opportunities surrounding climate changeSolutions – delivers carbon reduction solutionsInnovations – develops low carbon technologiesEnterprises – creates low carbon businessesInvestments – nances clean energy businesses

www.carbontrust.co.uk0800 085 2005

The Carbon Trust is funded by the Department for Environment, Food and Rural Affairs (Defra),the Department for Business, Enterprise and Regulatory Reform, the Scottish Government, the WelshAssembly Government and Invest Northern Ireland.

Whilst reasonable steps have been taken to ensure that the information contained within this publicationis correct, the authors, the Carbon Trust, its agents, contractors and sub-contractors give no warrantyand make no representation as to its accuracy and accept no liability for any errors or omissions.Any trademarks, service marks or logos used in this publication, and copyright in it, are the propertyof the Carbon Trust. Nothing in this publication shall be construed as granting any licence or right to useor reproduce any of the trademarks, service marks, logos, copyright or any proprietary information inany way without the Carbon Trust’s prior written permission. The Carbon Trust enforces infringementsof its intellectual property rights to the full extent permitted by law.

The Carbon Trust is a company limited by guarantee and registered in England and Wales under

Company number 4190230 with its Registered Ofce at: 8th Floor, 3 Clement’s Inn, London WC2A 2AZ.Printed on paper containing a minimum of 75% recycled, de-inked post-consumer waste.

Published in the UK: April 2008

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