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P30405 Post Occupancy Evaluation. Sustainable / Building Energy Audit. Thackley End, Oxford. Student: Andrea Luise Schrader. Tutor: Dr Rajat Gupta. Oxford Brookes University.
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ENVIRONMENTALAUDIT.
ENVIRONMENTALAUDIT
CONTENTS.
GlobalEnvironmentalImpact.
LocalEnvironmentalImpact.
CalculatedBuildingFabricHeatLoss.
Transportation.
WasteManagement.
Recycling.
InternalEnvironment.
NaturalLightLevels.
SoundLevelRecordings.
RelativeHumidity.
InternalTemperature.
Recommendations.
GlobalEnvironmentalImpact.
CO2EmissionsPerAnnum.
Belowweseethedataexpressingtheenergyuseandconsequential carbon dioxide emissions produced by
theindividualcasestudyflatsofThackleyEndperyear(Top).
Theaverageusedherein,forcarbondioxideemissionsfrom electricity use, is 0.55kg per kWh of electrical
energyused(Gupta,2008).Thisconversioninfersthattheenergyloadfor10100wattbulbsturnedonforan
hour,wouldproducecarbonemissionsof1/5kg.
Comparing this conversion rate of CO2/energy forelectricity,tothegasconversionrateof0.19kgofCO2per kWh (Gupta, 2008)1, we can see that the
environmental impact of gas ismuch less. The graphshown (Central) indicated the possible carbonfootprint for the individual case study flats had gas
beenusedasthesourceofenergy.
This last graph (Below) illustrates the comparison oftheresultantCO2footprintofgasandelectricalenergysourcing (forThackleyEndcase study flats). It canbe
seenthatallcasestudyflatsperformbadlyinregardstoenvironmentalimpact.Gupta(2008)statesthatitisbadforabuildingtoemitmorethan75kgofCO2per
m2 of floor area.With the electrical energy / CarbonKg conversiononlyoneof the flats (Flat 10) is belowthisthreshold.However,bysourcingtheheatingfrom
gas energy, the CO2 emissions would be greatlyreduced, resulting in ¾ flats being below the 75kg ofCO2 per m2 level.
1Gupta,R.,2008,PostOccupancyEvaluationLectures,10–12/2008,OxfordBrookesUniversity
LocalEnvironmentalImpact.
WaterEfficiency.
A reduced water consumption is beneficial to theenvironment.Environmentallyfriendlyusageofwateris
nottorestrictuse,buttoreducewastage.2
ThackleyEndwaterconsumptionismeteredbyasinglecentralmeter.
ThackleyEndWaterConsumption:8420Litres(perday/totalsite)
153Litres(perday/flat)
IndustryStandardConsumptionperflat:3148Litres(perday/flat)
TheThackleyEndcasestudyflatshadfewwaterefficientappliancesfitted.Thiswouldthereforeresult
in a highr rater of unnecessary water wastage. Occupants did stress interest in improving waterefficiency. Evidence of this keenness to conserve water amongst residents is the use of rainwaterrecycling tanks, on ground floor level that is presumed to be used to water the communal garden
spaces.
Appliances.
Energy efficient appliances can reduce water consumption as well as conserve energy (Waterwise,2006).TheintroductionoftheEUEnergyLabel,broughtintopracticein1996(broughtaboutbytheEU
CouncilDirective92/75/EEC,1992)hadbroughtaboutmandatoryratingofhouseholdapplianceenergyratingbetweenthebandsofA‐G.
AppliancesinthecasestudyflatswerenotallofoptimumArating.Improvingthiswouldimprove,and
consequentlyreduce,waterconsumptionandwastage.FurtherdetailsontheappliancesoftheThackleyEnd case study flats can be found in the Occupant Survey later in this document.2Waterwise(2006)http://www.waterwise.org.uk/reducing_water_wastage_in_the_uk/house_and_garden/saving_water_at_home.html3OxfordshirePartnership(2007)“Oxfordshire’sSustainableCommunityStrategy,Alongtermvisionforthe
county.Briefingpaper6:Environment”
Washingmachinetype Energyrating Energyusagelimitperkgat60oC
Litresperwashbasedon5kgload
Indesit1600WIXE167 A <0.19kWh 30litres
HooverSE220 A <0.19kWh 30litres
UnknownMake A <0.19kWh 30litres
MieleNovotronicW864 D <0.34kWh Approx50litres
UnknownMake D <0.34kWh Approx50litres
Table 1: European energy label ratings. Energy labels: helping you make the right choice. Defra, 2005
Materials.
The buildings of the Thackley End site showed
considerable issues that would be detrimental toenergy conservation. The notable concerns werecold bridging through the specified single glazing
andmetalwindow frames and exposed structuralconcreteblockwork.
Externalwalls:
Dualskinof100mmconcreteblockswitha50mmcavity inbetween. Itmustbenotedthatthecavity
does not run the full height of the wall.In someplacesthere isnothermalbreakbetween internaland external surfaces (this would result in cold
bridging).Someoccupantshavereducedtheirheatlossesbyinstallinginsulationintothiscavitywhichhasprovensuccessful.
The floor slab is a 255m thick concrete slab that
runs through the building continuously frominternaltoexternalsurfaces.Whenwarmairrisesinsidetheflatstheheatenergyconductsthroughthisslabandoutofthebuilding.Severaloftheinternal
walls also penetrate to the external environment.Thiscoldbridgingisadetrimentalformofheatloss.
Illustration 1: Building fabric and cold bridging
Whilst itcanbearguedthatadditionalheat lossmethods insummermonths(andperiodsofextremesolar gain) could be beneficial, this conduction of energy through the building fabric promotes the
penetrationofmoistureintheairintomaterialswhichisundesirable.
Thesingleglazingofthebuildingsoriginalspecifications, thatsomeoftheflatsstillhave,arecauseofconsiderable energy losses. As mentioned before, the single glazing promotes considerable energylosses when the internal / external ratio is high. The high amounts of single glazing also promotes
considerableheatgains inperiodsofhighsolar irradiation, furtheraffectedbythe limitedamountsofshadingontheseglazedsurfaces.
Some residents replaced this existing single glazing (and it’s metal frame which also has a highconductance)withdoubleandtripleglazingtocombatthisheatloss.
Evidence of these extreme solar gains can be seen in the colour bleaching of the soft furnishings
(notably the curtains) in the areas around the glazing in the flats. The curtains in Flat 38 wereparticularlyaffectedinthisway.
This photo illustrates the colour bleaching in the living room curtains of Flat 38.
CalculatedBuildingFabricHeatLoss.
Flat10.
TheSankeydiagramandresultantpiechartillustratestheheatenergyincontactanddistributedwithin/throughtheflatinquestion.TheSankey
diagramshowsevendistributionofenergylossesthroughthewindowandwalls.ThisisexplainedbythesimilarareaandUvaluesofbothexposedwallsandwindows.
Atacostof£0.09perkWhofelectricity(Gupta,2008),flat10islosing£1.80perannuminwastedheat,andemitting11kgthroughlostheat.
Flat29.
ItcanbeassumedthatthegreaterpartoftheheatlossfromFlat29isconductedthroughtheroof:ithasalargeareaandconsiderablecoldbridgingissues.Thewindowsaredoubleglazedandthereforeshowareductioninlosseswhencomparedtothesingleglazedunits.
Atacostof0.09perkWhofelectricity(Gupta,2008),Flat29islosing£*.37perannuminwastedheat,andemitting51kgofCO2throughlostheat.
WindowArea:16.8m2
WindowUValue:2.7WallArea:15.2m2
WallUValue:3.03
RoofArea:46.64m2
RoofUValue:3.5WallArea:35m2
WallUValue:3.03
WindowArea:15.84m2WindowUValue:2.7
Flat38.
ThearearatioofwindowtowallinFlat38isverysimilartotheproportionsofFlat10.HoweverthewindowsinFlat38aresingleglazed(andconsequentiallyhaveahighUvalue)thereforeresultingina
higherrateofheatlossisthroughtheglazing.
Atacostof£0.09perkWhofelectricity(Gupta,2008),Flat38islosing£3.96perannuminwastedheat,andemitting22.55kgofCO2throughlostheat.
Flat50
AswithFlat29,itcanbeassumedthatthegreaterpartoftheheatlossfromFlat29isconductedthroughtheroof(ithasalargeareaandconsiderablecoldbridgingissues)withacalculated54.7kWhbeinglosteachyear.Thewindowsaredoubleglazedandthereforeshowareductioninlosseswhen
comparedtothesingleglazedunits.
Atacostof£0.09perkWhofelectricity(Gupta,2008),Flat29islosing£9.36perannuminwastedheat,andthereforeemitting57.2kgthroughlostheat.
WallArea:15.2m2WallUValue:3.03
WindowArea:16.02m2
WindowUValue:5.6
WindowArea:16.8m2
WindowUValue:2.7WallArea:34.32m2
WallUValue:3.03
Transportation.
AvailablepublictransporttoThackleyEndSite:
BusRoutes:
2,7Services:OxfordandKidlington.
27,59Services:Oxford,Bicester/WaterEtonPark&Ride.
BusStoplocatedverynearthe
ThackleyEnddriveway.
Thackley End occupants were asked if they used the buses; 10/11 saidtheydid.Thepurposesoftheirbususewereasfollows:
Travellingtowork:4/11 Otherdailyactivities:4/11
WeekendLeisure:6/11From the case study resident’s opinion, we were able to assume that
manyoftheoccupantsofThackleyEndcycle.Thereisabikestoreonthedevelopment,andanotherisbeingbuiltbypopulardemand.
Bicycle Overflow from bike store
WasteManagement.
Thewastebins are emptiedweekly by theOxfordshireCity Council. Residents dispose of waste via rubbishchutes thatare locatedon the first landing levelof the
stairwell.Theseareutilizedbythemajorityofoccupantsasked, however there were concerns regarding beingunabletoseeifthewastestorebelowisfull.
Thereisrealconcernthattheeasy‐accesschutesystem
may discourage residents to walk to the bins furtherawayonsitatgroundfloorlevel.
Recycling.
Survey results showeda largemajorityof the residentsof Thackley End actively recycle. There is a generousrecycling unit that caters for all recycling needs and
materials such as glass, plastics,metal cans, paper andcardboard. The Oxford City Council empties the binsweekly.
Thereisalsoacompostingfacilityavailabletoresidents
butitisnotaswellusedastheotherrecyclingfacilities.
Bothrecyclingandwastemanagementarecoveredin
greaterdetailintheOccupantSurveylateroninthisdocument.
InternalEnvironment.
InternalCarbonDioxideLevels.
ComparingtheunitstobenchmarksitbecameclearthattheflatsinThackleyEndwereabovetheCIBSEgoodairqualitylevel.GenerallytheCO2ratingseitherreachedorjustexceededtheBSRIAcontrollevelforacceptableindoorqualityforshorttermexposure.Theseundesirablelevelsofcarbondioxidewould
ordinarilybeacauseforconcern.Howeveranomalies intheresultscouldhavebeencausedfromtheconsiderable increase in human activity – and consequential CO2 levels from the research team’sinteractionwiththeinternalflatenvironment.
ThehigherlevelsofCO2couldbecauseofpoorventilationintheflats.Thelateroccupantsurveygives
indicationtothisbeingapossibility.Occupantsseemedconcernedofheatlossesoverventilationneedswithinwintermonths and consequently overlook air quality in favour of reducing heating gains. TherecordingsweretakeninOctoberwhenthiswouldhavebeenthecase.
It however must be noted that, whilst CO2 levels are higher than the optimum level, they are not
significantlyhazardous.
Carbondioxideconcentrationpermillionparticules
Levels
300‐400 Typicalbackground(atmospheric)concentrations
600 Goodindoorairquality
800 BSRIAcontrollevelforacceptableindoorairquality(short‐termexposure)
1000 WHO(1984)concentrationoflimitedornoconcern(short‐termexposure)
NaturalLightLevels.
Theflatsseemedtohavebeendesignedwiththeintentionofallowingconsiderablelightpenetrationononefaçade(throughfloortoceilingglazing),tobleedintotheinternalspacescausinghighvisibilityand
thermaldelight.Theopposingfaçadeoffers lessnatural lightingaswindowscouldbeaprivacybreachduetothewalkwayastridetheentrancesandfacades.Thishashadthedetrimentaleffectofmakingtheinternalspacesconnectedtothisfaçade–oftenthebathroomandkitchen–darker.Thisglazedbalcony
accessed facade has also led to problems; the glazing causes uncomfortably high heat gains in thesummer months and consequential bleaching of the hard and soft furnishings. The glazing also isaccredited to severe heat losses in the evenings and winter months. These extreme reactions to
temperatureandsolargainareheightenedintheflatsthatstillutilizetheoriginalsingleglazing.
Thebelowgraphshowstheaverageddaylightfactorsinthreekeyenvironmentsinthefourflatsthatlightinglevelswererecordedin.
CIBSEDaylightFactorGrading:4
TooDark/CauseForArtificialLight:0‐2%ComfortableDaylightfactor:2‐5%
TooBright/CauseForGlare:+5%Surprisingly,consideringthehighwalltowindowratiosoftheflatstheoverallconsensusisthattheflats
are too dark. The light penetrates into the window at a considerable level, but attenuates quickly.Artificial lighting is required to light the areas under 5%. It however must be noted that the abovereadingsweretakeninNovember,resulting inconsiderably lowersolar irradiance.Hadthesereadings
beentakeninpeaksummermonths,theAuthorbelievestherewouldbeconsiderableproofofglareinglazedspaces.
SoundLevelRecordings.
Soundqualitywasnotmuchcauseforconcern within the flats of ThackleyEnd. The author did not find external
noise pollution within the interiorspaces of the flats disturbing. Somelight traffic noises could be heard but
nothingtoointrusive.
There was a slight increase in trafficnoises in the blocks closest to theBanbury Road, but nothing of a
considerablelevel.
4CIBSE(1997)“BritishLightingGuide”UK
Itshouldbenotedhowever,betweensomeofthebuildingswithintheThackleyEnddevelopmenttherewasslightechoingofsound.Thismayaccentuatethesoundsofcarspassingintothedevelopmentthat
couldbeaudiblethroughthesingleglazedbedroomwindowsfrontingthecarparkingspacesanddrives.Occupantshoweverdidnotpasscomment.
Table 2: dBa volume levels,
Mike Wilson, sound physics
lecture on 03/11/08
Table 3: dBa volume levels
recommended by CIBSE
Guide A : Environmental
Design,2008
RelativeHumidity.
Due to occupants concern for heat retention in winter months (as a result of considerable losses
through glazing and cold bridging), there is a considerable reduction in ventilation. This results inhumidityfromcooking/bathroomactivity,thatisunabletopassoutintotheexternalenvironment.
Itislaterrecorded,intheOccupantSurvey,thatcondensationoftenformedontheinternalsurfacesoftheglazing, inferringahighhumidity in the coldwinterperiods. Theauthornotedoneof the flats to
haveadehumidifierinthemonthofOctober.
Occupants were also recorded in saying that, during summermonths, the flats were well ventilated(fromactingagainsttheincreasingsolargains),andthereforetheinternalspacessufficientlypenetratedbyfreshairforhumiditytocollectorsettle.
DecibelVolume Comparisons
61dBa levelofaconversation
84dBa levelforstreettraffic
100dBa levelforapneumaticdrillat7mdistance
DecibelVolume Comparisons
31dBa levelforabedroom
36dBa levelforalivingroom
41dBa levelforalibrary,bank,museum
64dBa levelofalightengineeringworkshop
InternalTemperature.
Flat10.
Thetemperature inFlat10remains relativelyconstant.Despitesomefluctuation, itdoesnotseemtoalter temperature too rapidly in comparison to other flats. The occupant does not use under‐floor
heatingwhichwould ordinarily insinuate a constant regulated temperature, but uses a large electricheater to caterhis thermalneeds. Itmust alsobenoted that this flat is considerably colder than theothers,whichbringstheinternalclosertotheexternaltemperature,resultinginalessrapidheatloss.
Flat29.
Flat29showserraticchanges intemperature,notably inthediningandlivingroomareasthatshowasteep incline / increase in temperature in themornings. The occupant complained of excessive solargainsresultinginuncomfortablesolargain.Thisdatagivesevidenceofthis.Theoccupantcombatedthis
problembyclosinginternalcurtainstoscreenfromthesun.Thishoweverdoesnot impedesolargains
andalthoughperceivedcomfortisimproved,thetemperatureisstillincreasing.
GraphforFlat29overleaf.
Flat38.
Flat 38 is heated by under floor heating that is turned on between 7pm and 7am using off peak(cheaper)electricalpower inthenighttimehours.Kitchenand livingareasshowagradual increase in
temperatureintheeveningtoapeakataround10.30.Thetemperaturethengraduallydecreasesduringthe day. This is not to the occupants satisfaction who claimed to be uncomfortably warm on somemorningsanduncomfortablycoldinsomeevenings.
Flat38showsfluctuationsinthelivingroomarea.Thesesteadychangesoftemperaturebetween24.5–21oC(atworst),giveafluctuatingtemperaturedifferenceof3.5oCwhichisoutsidetherecommended
limit.5 The orientation of the flat (predominantly glazed façade iswest facing) so there could also besomecauseoftemperature increaseaccreditedtosolargains.Thebedroomspace,separatefromtheliving / dining room spaces, seems to be amore constant temperature, which shouldmost likely be
resultanttoseparateheatingcontrolsandinternalpartitions(walls)allowingittomaintainaseparatethermalenvironment.
Recommendations.
NoCost
Improvethemanagementofthecompostheaptoencourageoccupantstoutilizethismethodofrecycling(notablyforfoodandgardenwaste)more.
Installcisterndisplacementdevicesintoiletstoreducewaterconsumption.
LowCost
Improveeaseofrecyclingbyaddingrecyclingchutestothestairwell,thereforeencouragingmoreoccupantstorecycle.
Installwaterefficientbathroomandkitchenfittingstoreducewaterwastageandconsequential
consumption.Pricesforketfixturesareasfollows:
Room Item Unitcost Totalcost
5Gupta,R.,2008,PostOccupancyEvaluationLectures,10–12/2008,OxfordBrookesUniversity
Bathroom Toiletwatersaver(ekohut,2008a) 12.33 x1=12.33
Efficientshowerhead(ekohut,2008b) 5.95 x1=5.95
Tapaerator(ekohut,2008c) 6.45 x2=12.9
Kitchen Tapaerator(ekohut,2008c) 6.45 x2=12.9
Totalperflat £44.08
MediumCost
Improvebicyclestoragefacilitiestoimproveoccupantsatisfactionandtoencouragecyclingover
otherlesssustainablemethodsoftransport.
Improvelightingintherearoftheflatsbyinstallingfrontdoorswithglazing(frostedifprivacyisaconcern):Costofafrontdoorwithglazingisapproximately£160.6
Upgrade washing machines and dishwashers to A Rated Energy Efficiency to reduce waterwastageandenergyconsumption:ARatedwashingmachineisapproximately£160.7
ARateddishwasherisapproximately£250.8
HighCost
Install double/triple glazing to replace single glazing. This reduces heat losses and thereforeenergyspaceheatingconsumptionandcosts.
Professional assessment of the high levels of carbon dioxide within the flats, and install any
resultantimprovedventilationifnecessary.
Install gas infrastructure for heating and cooking purposes to reduce CO2 emissions (asmentionedearlier (Gupta,R,2008)electricityproductionproducessignificantlyhigherratesofCO2perkWhthangas).ToretainsustainableethosofThackleyEndresidentstheenergysource
shouldideallybechanged.
6Doorwarehouse(2008)http://www.doorwarehouse.co.uk/showdoor2.php?args=EALIMA3U00~(A3)~(E)~
(.)~(001)~(M)~(.)~(.) UK. 7Amazon.co.uk(2008)Hotpoint‐FDW85A‐FDW85‐Dishwasher, http://www.amazon.co.uk/
Hotpoint‐FDW85A‐FDW85‐Dishwasher/dp/B0002TTKFU/ref=sr_1_4ie=UTF8&s=kitchen&qid
=1229223576&sr=1‐4.UK.Accessed13December2008.
8Amazon.co.uk(2008)Indesit‐Washing‐Machine‐WIA101, http://www.amazon.co.uk/Indesit‐Washing‐Machine‐WIA101/dp/B000ILZ286/ref=sr_1_1?ie=UTF8&s=kitchen&qid=1229223469&sr=1‐1 UK.Assessed13December2008.
Introducesolarshadingdevicestoreducetheinternalsolarheatgainsthataremajorcauseforconcern.Therecanbearangeofsolutionstoamendthis(externalshutters,glazinglaminates,
awningsetc.).Theestimatedaveragecost isapproximately£180/m.Thisresultstoanaveragecostof£1296perflat.9
Reduce building fabric heat loss by over cladding with hempcrete. Cost: £145/m2. 10
9GreenSpec(2008)http://www.greenspec.co.uk/html/durability/solar_shading.html UK.Assessed13December.10Wilburn,G.(2008)“1960’s Concrete Framed Housing : Barriers and opportunities when sourcing materials from
within Oxfordshire, to over‐clad and improve the envelopes’ thermal performance.”UK.
Room Item Unitcost Totalcost
Bathroom Toiletwatersaver(ekohut,2008a) 12.33 x1=12.33
Efficientshowerhead(ekohut,2008b) 5.95 x1=5.95
Tapaerator(ekohut,2008c) 6.45 x2=12.9
Kitchen Tapaerator(ekohut,2008c) 6.45 x2=12.9
Totalperflat £44.08