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Tobecomfortable,buildingsinallAustralianclimatesrequiresomeformofcoolingatsometimeoftheyear.Therearemanywaysyoucandesignormodifyyourhometoachievecomfortthroughpassive(nonmechanical)cooling,aswellashybridapproacheswhichutilisemechanicalcoolingsystems.
Themostappropriatepassivecoolingstrategiesforyourhomeincludingorientation,ventilation,windows,shading,insulationandthermalmassaredeterminedbyclimate,sofirstidentifyyourclimatezonebyreadingDesignforclimate.YoucanthenapplythemoredetailedadvicehereandinPassivesolarheating.
AllAustralianclimatesapartfromtropical(Zone1)requiresomeformofheatinginwinter,andthisaffectsadvicerelatingtocooling.Thebalancebetweensummercoolingandwinterheatingshouldbeadjustedforclimatethroughappropriatepassivedesign.Tropicalclimatebuildings,whichrequireyearroundshadingandaresubjecttoverydifferentpassivecoolingprinciples,arediscussedseparatelybelow.
Theadviceinthisarticleappliestomosttypesofresidentialhousinghowever,additionalusefultipscanbefoundinBuyingahomeofftheplan,Buyinganexistinghome,RenovationsandadditionsandBuyingandrenovatinganapartment.
Passivecooling
Passivecooling(/sites/prod.yourhome.gov.au/files/pdf/YOURHOME2PassiveDesign5PassiveCooling(4Dec13).pdf)
[PDF2.2MB]
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Photo:SuntechDesign
Verandas,underfloorventilationandshadyplantingskeepthisDarwinclassiccomfortableintheheat.
Heatwavescanaffectlargeregionsatthesametime,causingcombinedhouseholddemandforcoolingenergytopeakforafewdaysorweekseachyearduetoincreaseduseofairconditioningorheatpumpsforcoolingduringtheseperiods.However,withcarefuldesignforpassivecoolingwemaydelayoreliminatethispeakdemand.
Whatispassivecooling?Passivecoolingistheleastexpensivemeansofcoolingahomeinbothfinancialandenvironmentalterms.SomelevelofpassivecoolingisrequiredineveryAustralianclimateatsometimeoftheyear.
Ascoolingrequirementsaredictatedbyclimate,distinctlydifferentapproachestopassivecoolingarerequiredfor:
hothumidclimates(Zone1)wherenoheatingisrequiredtemperateandwarmclimates(Zones26)wherebothheatingandcoolingarerequiredcoolandcoldclimates(Zones78)whereheatingneedsaremoreimportant.
Eachclimateisdiscussedseparatelybelow.
CoolingpeopleFactorsaffectingcomfortforpeople(humanthermalcomfort)areoutlinedinDesignforclimateandincludebothphysiologicalandpsychologicalfactors.
Tobeeffective,passivecoolingneedstocoolboththebuildingandthepeopleinit.
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Evaporationofperspirationisthemosteffectivephysiologicalcoolingprocess.Itrequiresairmovementandmoderatetolowhumidity(lessthan60%).
Radiantheatlossisalsoimportant,bothphysiologicallyandpsychologically.Itinvolvesdirectradiationtocoolersurfaces.
Conductioncontributestobothtypesofcomfortandinvolvesbodycontactwithcoolersurfaces.Itismosteffectivewhenpeoplearesedentary(e.g.sleepingonawaterbed).
CoolingbuildingsTheefficiencyofthebuildingenvelopecanbemaximisedinanumberofwaystominimiseheatgain:
shadingwindows,wallsandroofsfromdirectsolarradiationusinglightercolouredroofstoreflectheatusinginsulationandbufferzonestominimiseconductedandradiatedheatgainsmakingselectiveorlimiteduseofthermalmasstoavoidstoringdaytimeheatgains.
Tomaximiseheatloss,usethefollowingnaturalsourcesofcooling:
airmovementcoolingbreezesevaporationearthcouplingreflectionofradiation.
CoolingsourcesSourcesofpassivecoolingaremorevariedandcomplexthanpassiveheating,whichcomesfromasingle,predictablesourcesolarradiation.
Varyingcombinationsofinnovativeenvelopedesign,airmovement,evaporativecooling,earthcoupledthermalmass,lifestylechoicesandacclimatisationarerequiredtoprovideadequatecoolingcomfortinmostAustralianclimatezones.Additionalmechanicalcoolingmayberequiredinhothumidclimatesandinextremeconditionsinmanyclimates,especiallyasclimatechangeleadstohighertemperaturesduringthedaytimeandovernight.
AirmovementAirmovementisthemostimportantelementofpassivecooling.Itcoolspeoplebyincreasingevaporationandrequiresbothbreezecaptureandfansforbackupinstillconditions.
Italsocoolsbuildingsbycarryingheatoutofthebuildingaswarmedairandreplacingitwithcoolerexternalair.Movingairalsocarriesheattomechanicalcoolingsystemswhereitisremovedbyheatpumpsandrecirculated.Thisrequireswelldesignedopenings(windows,doorsandvents)andunrestrictedbreezepaths.
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Inallclimates,airmovementisusefulforcoolingpeople,butitmaybelesseffectiveduringperiodsofhighhumidity.Anairspeedof0.5m/sequatestoa3Cdropintemperatureatarelativehumidityof50%.Thisisaoneoffphysiologicalcoolingeffectresultingfromheatbeingdrawnfromthebodytoevaporateperspiration.Airmovementexposestheskintodryerair.Increasedairspeedsdonotincreasecoolingatlowerrelativehumiditybutairspeedsupto1.0m/scanincreaseevaporativecoolinginhigherhumidity.Airspeedsabove1.0m/susuallycausediscomfort.
CoolbreezesWheretheclimateprovidescoolingbreezes,maximisingtheirflowthroughahomewhencoolingisrequiredisanessentialcomponentofpassivedesign.Unlikecoolnightair,thesebreezestendtooccurinthelateafternoonorearlyeveningwhencoolingrequirementsusuallypeak.
Coolbreezesworkbestinnarroworopenplanlayouts.
Coolbreezesworkbestinnarroworopenplanlayoutsandrelyonairpressuredifferentialscausedbywindorbreezes.Theyarelesseffectivein:
buildingswithdeepfloorplansorindividualsmallroomslongperiodsofhighexternaltemperature(ambientorconductedheatgainsabove3540wattspersquaremetre(W/m
)locationswithhighnoise,securityriskorpoorexternalairquality,wherewindowsmayneedtobeclosed.
Coastalbreezesareusuallyfromanonshoredirection(southeastandeasttonortheastinmosteastcoastareas,andsouthwestinmostwestcoastareas,e.g.theFremantleDoctor).
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Inmountainousorhillyareas,coolbreezesoftenflowdownslopesandvalleysinlateeveningandearlymorning,asheatradiatingtoclearnightskiescoolsthelandmassandcreatescoolaircurrents.
Thermalcurrentsarecommoninflatter,inlandareas,createdbydailyheatingandcooling.Theyareoftenofshortdurationinearlymorningandeveningbutwithgooddesigncanyieldworthwhilecoolingbenefits.
CoolnightairCoolnightairisareliablesourceofcoolingininlandareaswherecoolbreezesarelimitedanddiurnaltemperaturerangesusuallyexceed68C.Hotairradiatingfromabuildingfabricsthermalmassisreplacedwithcoolernightairdrawnbyinternalexternaltemperaturedifferentialsratherthanbreezes.Fullheight,doublehungwindowsareidealforthispurpose.Furthercoolingcanbegainedbyincludingwholeofhousefans(seebelow).
ConvectiveairmovementTheruleofconvection:warmairrisesandcoolairfalls.
Stackventilation,orconvectiveairmovement,reliesontheincreasedbuoyancyofwarmairwhichrisestoescapethebuildingthroughhighleveloutlets,drawinginlowerlevelcoolnightairorcoolerdaytimeairfromshadedexternalareas(south)orevaporativecoolingpondsandfountains.
Convectioncauseswarmairtorise,drawingincoolair.
Convectiveairmovementimprovescrossventilationandovercomesmanyofthelimitationsofunreliablecoolingbreezes.Evenwhenthereisnobreeze,convectionallowsheattoleaveabuildingviaclerestorywindows,roofventilatorsandventedridges,eaves,gablesand
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ceilings.
Convectionproducesairmovementcapableofcoolingabuildingbutusuallyhasinsufficientairspeedtocoolpeople.
SolarchimneysSolarchimneysenhancestackventilationbyprovidingadditionalheightandwelldesignedairpassagesthatincreasetheairpressuredifferential.Warmedbysolarradiation,chimneysheattherisingairandincreasethedifferenceintemperaturebetweenincomingandoutflowingair.
Theincreaseinnaturalconvectionfromthesemeasuresenhancesthedrawofairthroughthebuilding.
Source:GreenBuilderSolarGuidelines(Residential)
Solarchimneysenhanceventilation.
EvaporativecoolingAswaterevaporatesitdrawslargeamountsofheatfromsurroundingair.Evaporationisthereforeaneffectivepassivecoolingmethod,althoughitworksbestwhenrelativehumidityislower(70%orlessduringhottestperiods)astheairhasagreatercapacitytotakeupwatervapour.
Ratesofevaporationareincreasedbyairmovement.
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Pools,pondsandwaterfeaturesimmediatelyoutsidewindowsorincourtyardscanprecoolairenteringthehouse.Carefullylocatedwaterfeaturescancreateconvectivebreezes.Thesurfaceareaofwaterexposedtomovingairisalsoimportant.Fountains,mistspraysandwaterfallscanincreaseevaporationrates.
Photo:SunpowerDesign
Pondsprecoolairbeforeitentersahouse.
Mechanicalevaporativecoolersarecommonindrierclimatesandinlandareaswhererelativehumidityislow.Theyuselessenergythanrefrigeratedairconditionersandworkbetterwithdoorsandwindowsleftopen.Theirwaterconsumptioncanbeconsiderable.(seeHeatingandcooling)
EarthcouplingEarthcouplingofthermalmassprotectedfromexternaltemperatureextremes(e.g.floorslabs)cansubstantiallylowertemperaturesbyabsorbingheatasitentersthebuildingorasitisgeneratedbyhouseholdactivities.
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Earthcouplingutilisescoolergroundtemperatures.
Passivelyshadedareasaroundearthcoupledslabskeepsurfacegroundtemperatureslowerduringthedayandallownighttimecooling.Poorlyshadedsurroundscanleadtoearthtemperaturesexceedinginternalcomfortlevelsinmanyareas.Inthisevent,anearthcoupledslabcanbecomeanenergyliability.
GroundandsoiltemperaturesvarythroughoutAustralia.Earthcoupledconstruction(includingslabongroundandearthcoveredorbermed)utilisesstablegroundtemperaturesatlowerdepthstoabsorbhouseholdheatgains.
PassivecoolingdesignprinciplesToachievethermalcomfortincoolingapplications,buildingenvelopesaredesignedtominimisedaytimeheatgain,maximisenighttimeheatloss,andencouragecoolbreezeaccesswhenavailable.Considerationsinclude:
designingthefloorplanandbuildingformtorespondtolocalclimateandsiteusingandpositioningthermalmasscarefullytostorecoolness,notunwantedheatchoosingclimateappropriatewindowsandglazingpositioningwindowsandopeningstoenhanceairmovementandcrossventilationshadingwindows,solarexposedwallsandroofswherepossibleinstallingandcorrectlypositioningappropriatecombinationsofbothreflectiveandbulkinsulationusingroofspacesandoutdoorlivingareasasbufferzonestolimitheatgain.
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Integrationofthesevariablesinclimateappropriateproportionsisacomplextask.Energyratingsoftware,suchasthataccreditedundertheNationwideHouseEnergyRatingScheme(NatHERS),cansimulatetheirinteractioninanydesignfor69differentAustralianclimatezones.
WhiletheNatHERSsoftwaretoolsaremostcommonlyusedtorateenergyefficiency(thermalperformance)whenassessingahousedesignforcouncilapproval,theircapacity,innonratingmode,asadesigntooliscurrentlyunderused.Seekadvicefromanaccreditedassessor(AssociationofBuildingSustainabilityAssessors(http://www.absa.net.au/)orBuildingDesignersAssociationofVictoria(http://www.bdav.org.au/))whoisskilledinusingthesetoolsinnonratingmode.
EnvelopedesignfloorplanandbuildingformEnvelopedesignistheintegrateddesignofbuildingformandmaterialsasatotalsystemtoachieveoptimumcomfortandenergysavings.
Heatentersandleavesahomethroughtheroof,walls,windowsandfloor,collectivelyreferredtoasthebuildingenvelope.Theinternallayoutwalls,doorsandroomarrangementsalsoaffectsheatdistributionwithinahome.
Gooddesignoftheenvelopeandinternallayoutrespondstoclimateandsiteconditionstooptimisethethermalperformance.Itcanloweroperatingcosts,improvecomfortandlifestyleandminimiseenvironmentalimpact.
AllAustralianclimatescurrentlyrequiresomedegreeofpassivecoolingwithclimatechangethisisexpectedtoincrease.
Variedresponsesarerequiredforeachclimatezoneandevenwithineachzonedependingonlocalconditionsandthemicroclimateofagivensite.
Maximisetheindooroutdoorrelationshipandprovideoutdoorlivingspacesthatarescreened,shadedandrainprotected.Maximiseconvectiveventilationwithhighlevelwindowsandceilingorroofspacevents.Zonelivingandsleepingareasappropriatelyforclimateverticallyandhorizontally.Locatebedroomsforsleepingcomfort.Designceilingsandpositionfurnitureforoptimumefficiencyoffans,coolbreezesandconvectiveventilation.Locatemechanicallycooledroomsinthermallyprotectedareas(i.e.highlyinsulated,shadedandwellsealed).
ThermalmassThermalmassisthestoragesystemforwarmthandcoolth(theabsenceofwarmth)inpassivedesign.
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Climateresponsivedesignmeanspositioningthermalmasswhereitisexposedtoappropriatelevelsofpassivesummercooling(andsolarheatinginwinter).Badlypositionedmassheatsupandradiatesheatwellintothenightwhenexternaltemperatureshavedropped.Asaruleofthumb,avoidorlimitthermalmassinupstairssleepingareas.Inclimateswithlittleornoheatingrequirement,lowmassisgenerallythepreferredoption.(seeThermalmass)
Earthcoupledconcreteslabsongroundprovideaheatsinkwheredeepearthtemperatures(at3mdepthormore)arefavourable,butshouldbeavoidedinclimateswheredeepearthtemperaturescontributetoheatgain.Intheseregions,useopenventedfloorswithhighlevelsofinsulationtoavoidheatgain.
Inregionswheredeepearthtemperaturesarelower,considerenclosingsubfloorareastoallowearthcouplingtoreducetemperaturesandthereforeheatgains.
WindowsandshadingWindowsandshadingarethemostcriticalelementsinpassivecooling.Theyarethemainsourceofheatgain,viadirectradiationandconduction,andofcooling,viacross,stackandfandrawnventilation,coolbreezeaccessandnightpurging.(seeGlazingShading)
Lowsunanglesthrougheastandwestfacingwindowsincreaseheatgain,whilenorthfacingwindows(southintropics)transmitlessheatinsummerbecausethehigheranglesofincidencereflectmoreradiation.
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Source:AssociationofBuildingSustainabilityAssessors(ABSA)
Relationshipbetweensunangleandheatgain.
AirmovementandventilationDesigntomaximisebeneficialcoolingbreezesbyprovidingmultipleflowpathsandminimisingpotentialbarrierssingledepthroomsareidealinwarmerclimates.
Becausebreezescomefrommanydirectionsandcanbedeflectedordiverted,orientationtobreezedirectionislessimportantthantheactualdesignofwindowsandopeningstocollectanddirectbreezeswithinandthroughthehome.
Usecasementwindowstocatchanddeflectbreezesfromvaryingangles.
Source:DeptofEnvironmentandResourceManagement,Qld
Forbreezecollection,windowdesignismoreimportantthanorientation.
Winddoesntblowthroughabuildingitissuckedtowardsareasoflowerairpressure.Todrawthebreezethrough,uselargeropeningsontheleeward(lowpressureordownwind)sideofthehouseandsmalleropeningsonthebreezeorwindward(highpressureorupwind)side.Openingsnearthecentreofthehighpressurezonearemoreeffectivebecausepressureishighestnearthecentreofthewindwardwallanddiminishestowardtheedgesasthewindfindsotherwaystomovearoundthebuilding.
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Airflowpatternandspeedfordifferentopeningareas.
Inclimatesrequiringwinterheatingtheneedforpassivesolarnorthsuninfluencestheseconsiderationsdesignersshouldstriveforabalancedapproach.
Thedesignofopeningstodirectairflowinsidethehomeisacriticalbutmuchoverlookeddesigncomponentofpassivecooling.Size,type,externalshadingandhorizontal/verticalpositionofanyopenings(doorsandwindows)iscriticalasshowninthediagramsbelow.
Source:SteveSzokolay
Airflowpatternforwindowsofdifferentopeningheight.Louvrewindowshelptovaryventilationpathsandcontrolairspeed.
Considerinstallingalouvrewindowabovedoorstoletbreezespassthroughthebuildingwhilemaintainingprivacyandsecurity.Inclimatesrequiringcoolingonly,considerplacingsimilarpanelsaboveheadheightininternalwallstoallowcrossventilationtomovethehottestair.
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Positionwindows(verticallyandhorizonally)todirectairflowtotheareawhereoccupantsspendmosttime(e.g.diningtable,loungeorbed).
Inroomswhereitisnotpossibletoplacewindowsinoppositeoradjacentwallsforcrossventilation,placeprojectingfinsonthewindwardsidetocreatepositiveandnegativepressuretodrawbreezesthroughtheroom,asshowninthediagrambelow.
Usefinstodirectairflow.
Designandlocateplanting,fencesandoutbuildingstofunnelbreezesintoandthroughthebuilding,filterstrongerwindsandexcludeadversehotorcoldwinds.
Planttreesandshrubstofunnelbreezes.
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Planttreesandshrubstofunnelbreezes.
InsulationInsulationiscriticaltopassivecoolingparticularlytotheroofandfloor.Windowsareoftenleftopentotakeadvantageofnaturalcoolingandwallsareeasilyshadedroofs,however,aredifficulttoshade,andfloorsareasourceofconstantheatgainthroughconductionandconvection,withonlylimitedcoolingcontributiontooffsetit.
InsulationlevelsandinstallationdetailsforeachclimatezoneareprovidedinInsulationandInsulationinstallation.Paycarefulattentiontoupanddowninsulationvaluesandchooseappropriatelyforpurposeandlocation.
Inclimatesthatrequireonlycoolingorthosewithlimitedcoolingneeds,usemultiplelayersofreflectivefoilinsulationintheroofinsteadofbulkinsulationtoreduceradiantdaytimeheatgainswhilemaximisingnighttimeheatlossthroughconductionandconvection.Thisisknownastheonewayinsulationvalve.
Reflectivefoilinsulationislessaffectedbycondensationandishighlysuitedtocoolingclimateapplicationsasitreflectsunwantedheatoutwhilenotreradiatingitin.
Roofspace
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Wellventilatedroofspaces(andothernonhabitablespaces)playacriticalroleinpassivecoolingbyprovidingabufferzonebetweeninternalandexternalspacesinthemostdifficultareatoshade,theroof.
Wellventilatedroofspacesformabufferbetweeninternalandexternalareas.
Ventilatorscanreducethetemperaturedifferential(seePassiveheating)acrossceilinginsulation,increasingitseffectivenessbyasmuchas100%.Theuseoffoilinsulationandlightcolouredroofinglimitsradiantheatflowintotheroofspace.
Usecarefuldetailingtopreventcondensationfromsaturatingtheceilingandinsulation.Dewpointsformwherehumidaircomesintocontactwithacoolersurface,e.g.theundersideofroofsarkingorreflectivefoilinsulationcooledbyradiationtoaclearnightsky.(seeSealingyourhome)
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Source:COOLmob
Usingventilationtocooltheroofspace.
HybridcoolingsystemsHybridcoolingsystemsarewholehousecoolingsolutionsthatemployavarietyofcoolingoptions(includingairconditioning)inthemostefficientandeffectiveway.Theytakemaximumadvantageofpassivecoolingwhenavailableandmakeefficientuseofmechanicalcoolingsystemsduringextremeperiods.
FansFansprovidereliableairmovementforcoolingpeopleandsupplementingbreezesduringstillperiods.
At50%relativehumidity,airmovementof0.5m/screatesmaximumcoolingeffectfasterspeedscanbeunsettling.Asnotedabove,airspeedsupto1.0m/scanbeusefulinhigherrelativehumidity,butprolongedairspeedsabove1.0m/scausediscomfort.
Standardceilingfanscancreateacomfortableenvironmentwhentemperatureandrelativehumiditylevelsarewithinacceptableranges.Inalightweightbuildinginawarmtemperateclimate,theinstallationoffansinbedroomsandalllivingareas(includingkitchensandundercoveroutdoorareas)significantlyreducescoolingenergyuse.
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Source:AdaptedfromBallinger1992
Airmovementrelativetofanposition.
Fansshouldbelocatedcentrallyineachspace,oneforeachgroupingoffurniture.Anextendedlounge/diningareaneedstwofans.Inbedrooms,locatethefanclosetothecentreofthebed.Becauseairspeeddecreaseswithdistancefromthefan,positionfansovertheplaceswherepeoplespendthemosttime.(seeHeatingandcooling)
WholeofhousefansWholeofhouseorrooffansareidealforcoolingbuildings,particularlywherecrossventilationdesignisinadequate.However,theydonotcreatesufficientairspeedtocooloccupants.
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Source:Breezepower
Wholeofhousefansshouldbepositionedcentrally,e.g.intheroof,stairwellorhallways.
Typically,asinglefanunitisinstalledinacirculationspaceinthecentreofthehouse(hallwayorstairwell)todrawcooleroutsideairintothebuildingthroughopenwindowsinselectedrooms,whenconditionsaresuitable.Itthenexhauststhewarmairthrougheaves,ceilingorgableventsviatheroofspace.Thisalsocoolstheroofspaceandreducesanytemperaturedifferentialacrossceilinginsulation.
Controlsystemsshouldpreventthefanoperatingwhenexternalairtemperaturesarehigherthaninternal.
Drawinglargevolumesofhumidairthroughtheroofspacecanincreasecondensation.Adewpointformswhenthishumidaircomesincontactwithroofelements(e.g.reflectiveinsulation)thathavebeencooledbyradiationtonightskies(seeInsulationandSealingyourhomeforwaystomitigatethis).
Wholeofhousefanscanbenoisyatfullspeedbutaregenerallyoperatedintheearlyeveningwhencoolingneedspeakandhouseholdsaremostactive.Ifrunatalowerspeedthroughoutthenight,theycandrawcoolnightairacrossbedsthatarenearopenwindows,provideddoorsareleftopenforcirculation.Onstillnightsthiscanbemoreeffectivethanairconditioningfornighttimesleepingcomfort.
AirconditioningRefrigeratedairconditioninglowersbothairtemperatureandhumidityandprovidesthermalcomfortduringperiodsofhightemperatureandhumidity.However,itisexpensivetoinstall,operateandmaintain,andhasahigheconomicandenvironmentalcostbecauseit
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consumessignificantamountsofelectricityunlesshighefficiencyequipmentisusedinaveryhighperformancebuildingenvelope.Asitalsorequiresthehometobesealedofffromtheoutsideenvironment,occupantsareoftenunawareofimprovementsintheweather.
Airconditioningiscommonlyusedtocreatecomfortablesleepingconditions.Thenumberofoperatinghoursrequiredtoachievethermalcomfortcanbesubstantiallyreducedoreliminatedbycarefuldesignofnewhomes,aswellasalterationsandadditionstoexistinghomes.
Runningarefrigeratedairconditionerinaclosedroomforaboutanhouratbedtimeoftenlowershumiditylevelstothepointwhereairmovementfromceilingfanscanprovidesufficientevaporativecoolingtoachieveandmaintainsleepingcomfort.Someairconditioningunitssimplyoperateasfanswhenoutdoorambienttemperaturedropsbelowthethermostatsetting,sotheycanreplaceaceilingfan.
Efficientairconditioningrequiresmorethansimplyinstallinganefficientairconditioner.
Hybridcoolingsolutionsrequireadecisionearlyinthedesignstagesaboutwhetherairconditioningistobeusedandhowmanyroomsrequireit.Manyinefficientairconditioninginstallationsoccurwhentheyareaddedtoahomedesignedfornaturalcoolingasanafterthoughttoimprovecomfort.
DesignofairconditionedspacesThereisusuallynoneedtoairconditionallrooms.Decidewhichroomswillreceivemostbenefit,dependingontheiruse,andtrytoreducethetotalvolumeofairconditionedairspace(roomsize,ceilingheight).Oftenoneortworoomsaresufficienttoprovidecomfortduringperiodsofhighhumidityandhightemperatures.
Designfornighttimesleepingcomfortbyconditioningroomscommonlyusedintheearlyeveningwithbedroomsadjoining.Aconditioned,masonrywalltelevisionroominthecentreofafreerunning(passivelycooled)homewithsleepingspacesadjoiningitprovidesbothdirectandindirectcoolingbenefits.Efficient(lowheatoutput)lightingandappliancesareimportantinsuchanapplication.
Acoolmasonrywallinabedroomgivesbothpsychologicalandphysiologicalcomfortthroughcombinedradiantheatlossandreliableairmovementfromfans.
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Awellventilatedtropicalhouse.
Designconditionedroomswithhighlevelsofinsulationandlowestexposuretoexternaltemperatureinfluences,usuallyfoundinthecentreofthehouse.Adjoininglivingspacesshouldbewellventilated,freerunning(passivelycooled),withfanstoencourageacclimatisation,andprovideathermalbuffertoconditionedspaces.
Addresscondensationinexternallyventilatedroomssurroundingconditionedrooms.Wallswithhighthermalmasshavefewerdewpointproblemsthanlightweightinsulatedwallsandcanstorecoolth.
Wheninsulatedwallssurroundanairconditionedspace,avapourbarriershouldbeinstalledbetweenthewarmhumidairandtheinsulationmaterialtopreventtheinsulationbeingsaturatedbycondensation.Choosematerialsandfinishesthatareresistanttodamagefromcondensationforanyliningsplacedoverthevapourbarrier:placingreflectivefoilinsulationunderaplasterboardwalllining,forexample,causesthedewpointtoformundertheplasterboard.(seeSealingyourhome)
Avoidconditioningroomsthathavehighlevelindooroutdoortraffic.Alternatively,useairlockstominimisehotairinfiltrationorinstallanautomaticswitchingdevice(suchasareedswitchorothermicroswitch)tothedoorsleadingtotheairconditionedroomthatallowsoperationonlywhenthedoorisclosed.
OperationIdentifythemonthsandtimesofdaywhenmechanicalcoolingwillberequiredandusecontrolsystems,sensorsandtimerstoreducetotaloperatinghours.Turnairconditionersoffwhenyougoout.
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Setthermostatstothewarmestsettingthatstillachievescomfort.Experimentyoumayfind26Cquitecomfortablewhenyouthoughtyouneeded21C.
Adaptyourlifestylewherepossibletotakeadvantageofcomfortableexternalconditionswhentheyexist,tominimiseoperatingperiodsformechanicalcoolingsystems.
ClimatespecificdesignprinciplesClimatespecificdesignresponsesandpassivecoolingmethodsaredifferentfor:
hothumidclimates(Zone1)wherecoolingonlyisrequiredtemperateandwarmclimates(Zones26)wherebothheatingandcoolingarerequiredcoolandcoldclimates(Zones78)whereheatingneedsarepredominant.
Hothumidclimatesrequiringcoolingonly(Zone1)Duetotheuniquenatureofhothumidclimates,manystate,territoryandlocalgovernmentsintheseregionshaveproducedarangeofexcellentdesignresourcesandadvice(seeReferencesandadditionalreadingattheendofthisarticle).
Hothumidclimatesrequireafundamentallydifferentdesignapproach.
HothumidclimatesrequireafundamentallydifferentdesignapproachtothosecommonlyrecommendedthroughoutYourHome,whichfocusespredominantlyonclimatesrequiringbothsummercoolingandwinterheating.
Themostsignificantdifferenceisinthesizeandorientationofwindowsoropenablepanelsanddoors.Intheseclimates,modestamountsofwellshadedglazingcanandshouldbepositionedoneveryfaadetoencourageairmovement.
Windowsorotheropeningsshouldbelocated,sizedanddesignedtooptimiseairmovement,notsolaraccess.Asstatedearlier,winddoesntblowthroughabuildingitissuckedtowardsareasoflowerairpressure.Locatelargeropeningsonthedownwind,orleeward,sideofthehouseandsmalleropeningsonthebreeze,orwindward,side.Thisisadvantageousinthesecycloneproneregionssincecyclonesandcoolbreezescommonlycomefromanonshoredirection.(seeOrientation)
Otherelevationsshouldalsoincludeopeningsbecausebreezescomefromavarietyofdirectionsandcanberedirectedordivertedthroughgooddesignandappropriatewindowstyles,especiallycasementwindows.
Anothercriticaldifferenceisthatthedesignerneedstomakeanearlydecisionaboutwhetherthehomeistobefreerunning(i.e.passivelycooled),conditioned(mechanicallycooled)orhybrid(acombinationofboth).
Freerunningbuildingsshouldnotbeconditionedatafuturedatewithoutsubstantialalteration:thisincludesreducingthesizeofopenings,addingbulkinsulationaroundtheroom(s)tobeconditionedandcondensationdetailing.
Designresponsestothechallengesofhothumidclimates
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Highhumiditylevelsintheseclimateslimitthebodysabilitytoloseheatbyevaporatingperspiration.(seeDesignforclimate)
Sleepingcomfortisasignificantissue,especiallyduringperiodsofhighhumiditywherenighttemperaturesoftenremainabovethoserequiredforhumancomfort.Whileacclimatisationhelps,itisofteninadequateduringthebuildupandwetseasonespeciallyincitieswithhighlytransientpopulationssuchasDarwin.
Designresponsesconsidershading,airmovement,insulationandconstructionmethods.
ShadingPermanentlyshadeallwallsandwindowstoexcludesolaraccessandrain.Considershadingthewholebuildingwithaflyroof.Shadeoutdoorareasaroundthehousewithplantingsandshadestructurestolowerthegroundtemperatureandthencethetemperatureofincomingair.
AirmovementMaximiseexposureto(andfunnellingof)coolingbreezesontothesiteandthroughthebuilding,e.g.largerleewardopenings,smallerwindwardopenings.Usesingleroomdepthswherepossiblewithlargeopeningsthatarewellshadedtoenhancecrossventilationandheatremoval.Designunobstructedcrossventilationpaths.Providehotairventilationatceilinglevelforallroomswithshadedopenableclerestorywindows,whirlybirdsorridgevents.Elevatethebuildingtoencourageairflowunderfloors.Usehigherorrakedceilingstopromoteconvectiveairmovement.Designplantingstofunnelcoolingbreezesandfilterstrongwinds.Installceilingfanstocreateairmovementduringstillperiods.Considerusingwholeofhousefanswithsmartswitchingtodrawcooleroutsideairintothehouseatnightwhenthereisnobreeze.Choosewindowswithmaximumopeningareas(louvresorcasement)thatcanbetightlysealedwhenclosedavoidfixedglasspanels.Openableinsulatedpanelsandsecurityscreendoorscanbeusedinsteadofsomewindows.Uselightercoloursonroofandexternalwalls.
InsulationUseinsulationsolutionsthatminimiseheatgainduringthedayandmaximiseheatlossatnight,i.e.usemultiplelayersofreflectivefoiltocreateaonewayheatvalveeffectandavoidbulkinsulation.
ConstructionUselowthermalmassconstructiongenerally.Considerthebenefitsofhighmassconstructionininnovative,welldesignedhybridsolutions.
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Mixedclimatesrequiringheatingandcooling(Zones26)WelldesignedAustralianhomesdonotrequireairconditioninginmostclimates.
Morethan50%ofhomesinwarmtemperateclimatesaremechanicallycooled.Thisproportionisrapidlyincreasingoftenbecauseinadequateshading,insulationandventilation,orpoororientationandroomconfigurationforpassivecoolingandsuncontrol,causeunnecessaryoverheating.
Warmhumidclimates(Zone2)Energyconsumptionforheatingandcoolingcanaccountforupto25%oftotalhouseholdenergyuseinthisclimate.InbenignclimateslikethecoastalareasofsoutheastQueenslandandnortheastNSW,achievingthehighlevelsofpassivethermalcomfortrequiredtoreducethisbyasmuchas80%isarelativelysimpleandinexpensivetask.
Designandorientatetomaximisethecontributionofcoolingbreezes.Useearthcoupledconcreteslabonground.Providehighlevelsofcrossventilationviaunobstructedpathways.Useceilingfansandconvectiveventilationtosupplementthem.Includeawelllocatedandshadedoutdoorlivingarea.Uselightercoloursforroofandexternalwalls.Considerwholeofhousefansinthisclimate.Applyhybridcoolingprincipleswherecoolingisused.
Passivesolarheatingisrequiredduringwintermonthsandvariesfromverylittletosignificant.Integratepassiveheatingrequirementswithcoolbreezecapturebyprovidingpassiveoractiveshading(eavesorawnings)toallwindows.
Employwelldesignedshadingandinsulationtolimitheatgainandmaximisesummerheatlossinresponsetothespecificmicroclimate.(seeShading)
ConstructionUsehighmassconstructioninareaswithsignificantdiurnal(daynight)temperatureranges(usuallyinland)toprovidesignificantamountsoffreeheatingandcooling.Uselowmassconstructionwherediurnaltemperaturerangesarelow(usuallycoastal)toincreasetheeffectivenessofpassiveandactiveheatingandcooling.Elevatestructurestoincreaseexposuretobreezesinwarmernorthernregions.Eliminateearthcouplinginsouthernandinlandregions.Usebulkand/orreflectiveinsulationtopreventheatlossandheatgain.Useglazingwithalowtomediumsolarheatgaincoefficient(SHGC)andUvalue.
Hotdryclimateswithwarmwinter(Zone3)Usecourtyarddesignswithevaporativecoolingfromponds,waterfeaturesandactive(mechanical)evaporativecoolingsystems.Theyareidealforaridclimateswherelowhumiditypromoteshighevaporationrates.
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Useevaporativecoolingifmechanicalcoolingisrequired.Useceilingfansinallcases.Usehighmasssolutionswithpassivesolarwinterheatingwherewintersarecooleranddiurnalrangesaresignificant.Uselowmasselevatedsolutionswherewintersaremildanddiurnalrangesarelower.
Minimiseeastandwestfacingglazingorprovideadjustableexternalshading.Highmasslivingareasaremorecomfortableduringwakinghours.Lowmasssleepingareascoolquicklyatnight.Highinsulationpreventswinterheatlossandsummerheatgain.
Considerhighmassconstructionforroomswithpassivewinterheatingandlowmassforotherrooms.Shadeallwindowsinsummerandeastandwestwindowsyearround.Usewellsealedwindowsanddoorswithmaximumopeningareatooptimiseexposuretocoolingbreezesandexcludehot,dryanddustywinds.
Hotaridclimateswithcoolwinter(Zone4)Usehighthermalmassconstructiontocapitaliseonhighdiurnaltemperaturerangesbystoringbothwarmthandcoolth.
Usecompactformstominimisesurfacearea.Maximisebuildingdepth.Includecloseablestackventilationinstairwellsandthermalseparationbetweenfloorsintwostoreyhomes.Useshadedinternalcourtyardswithevaporativecoolingfeaturesinsinglestoreyhomes.Usesmallerwindowanddooropeningsdesignedfornighttimecoolingandcoolthermalcurrentswhereavailable.UselowUvaluedoubleglazingwithhighSHGC.Ensurethatthemajorityofglazingisnorthfacingandpassivesolarshaded.Avoidwestwindows.
Evaporativecoolingandactivesolarheatingsystemsreducetheneedforlarge,solarexposedglassareasforheating(i.e.activeratherthanpassiveheating).
TraditionalandinnovativecoolingmethodsforaridclimatesSpecialistpassiveandlowenergycoolingsystemshaveevolvedforhotdryclimateareasinotherpartsoftheworld(e.g.MiddleEast,Arizona)whicharealsoapplicabletoalargeportionoftheAustraliancontinent.
Theyintroducemoisturetobuildingstructures(suchasroofpondsorwatersprayedontoevaporativepads)andincorporatestacksorchimneysthatuseconvectiontoexhaustrisinghotairanddrawcooler,lowlevelairintothebuilding.Thisaircanbeevaporativelycooledby
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beingdrawnoverponds,orthroughmistspraysorundergroundlabyrinths.(Thesetowersaredominantelementsandarethereforeanintegralpartofthefundamentalarchitectureofthebuilding.)
ModernversionofanIranianBadgircoolingsystemwhereearthexchangeandevaporationprecoolincomingairdrawnbyasolarchimney.
Temperateclimates(Zones5and6)Withgooddesign,temperateclimatesrequireminimalheatingorcooling.Goodorientation,passiveshading,insulationanddesignforcrossventilationgenerallyprovideadequatecooling.Additionalsolutionsfromtherangeexplainedherecanbeusedwheresiteconditionscreatehighercoolingloads.
Designforcompactformincoolerzones,extendingtheeastwestaxisinwarmerzones(seeOrientation).Preferplanswithmoderatebuildingdepthtworoomsisideal.Designfortheimpactsofclimatechangeandconsiderhighlyefficientheatpumpsystemstocopewithincreasesinextremeweatherevents.Usethermalmasslevelsappropriatetotheamountofpassivecoolingavailable(coolbreezes,consistentdiurnalvariations)andusethermalmasstodelaypeakcoolingneedsuntilafterthepeakdemandperiod.Choosewindowopeningstylesandpositionwindowstoensuregoodcrossventilation.Orientateforpassivesolarheatinganddivertbreezes.Employlargernorthernandsouthernfaades.Designformoderateopeningswiththemajoritytothenorth.Useminimalwestfacingglazing(unlesswellshaded).Usemoderateeastfacingglazingandmoderatesouthfacingglazingexceptwherecrossventilationpathsareimprovedbylargeropenings.Usebulkandreflectivefoilinsulation.UselowtomediumUvalueandSHGCglazinginmilderareasanddoubleglazingwhereambienttemperaturesarehigher.
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Temperateclimatescallforgoodorientation,passiveshadingandcrossventilation.
Coolandcoldclimateswhereheatingdominates(Zones7and8)Zone7requirescarefulconsiderationofcoolingneedsbecauseclimatechangemodellingindicatesthatitislikelytobeimpactedbyclimatechangemorethanmostotherzones.
Thisnecessitatesashiftfromthecurrenthighthermalmassdesignpracticestomoderateorlowmassdesignswithcarefullycalculatedglasstomassratiostoavoidsummeroverheating.Highermasssolutionsremainusefulinhigheraltitudeandcolderregionswheresignificantdiurnalrangesarelikelytocontinuetoprovidereliablecoolinginallbutextremeweatherevents.
Winterheatingremainsthepredominantneedinallbutthewarmestregionsinthesezones.Passivesolarorientationandshadingiscritical.Onsiteswherepassiveheatingorcoolingaccessislimited,considerlowmass,highinsulationsolutionswithhighlyefficientreversecycleheatpumps.Giveincreasedattentiontothedesignofhighlevelcrossventilationfornightcooling.LowUvaluedoubleglazingwithhighSHGCishighlydesirableduetoitseffectivenessinbothsummerandwinter.Useawelldesignedcombinationofreflectivefoilandbulkinsulation.Usemodestareasofglazingwiththemajorityfacingnorthwheresolaraccessisavailable.Minimisewestfacingglazing.Passiveand/oractiveshadingofallglazingisessential.
AdaptinglifestyleApplicableinallclimates,especiallyhothumidandhotdry,adaptinglifestylemeansadoptingliving,sleeping,cookingandactivitypatternsthatrespondtoandworkwiththeclimateratherthanusingmechanicalcoolingtoemulateanalternativeclimate.
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Highhumidclimatespresentthegreatestchallengeinachievingthermalcomfortbecausehighhumiditylevelsreduceevaporationrates.(seeDesignforclimate)
Adaptinglifestylemeansworkingwiththeclimateratherthanusingmechanicalcoolingtoemulateanalternativeone.
Acclimatisationisasignificantfactorinachievingthermalcomfort.Mostpeoplelivingintropicalclimateschoosetodoso.Theyliketheclimateandknowhowtolivecomfortablywithinitsextremesbyadoptingappropriatelivingpatternstomaximisetheoutdoorlifestyleopportunitiesitoffers.
Sleepingcomfortatnightduringthehottestandmosthumidperiodsisasignificantissueformanypeoplelivingintropicalclimates.Sleepingcomfortgenerallyshouldbeahighprioritywhenchoosing,designingorbuildingahome.Differentmembersofahouseholdhavedifferentthermalcomfortthresholds.Childrenoftenadapttoseasonalchangesmoreeasilythanadultsdo.
Understandingthesleepingcomfortrequirementsofeachmemberofthehouseholdcanleadtobetterdesign,positioningorallocationofbedroomsandincreasedthermalcomfortforallwithlessdependenceonmechanicalcooling.
Liveoutsidewhentimeofdayandseasonalconditionsaresuitableparticularlyintheevenings.Radiationbythebodytocoolnightskiesisaneffectivecoolingmechanism,especiallyintheearlyeveningwhendaytimeheatloadshavenotbeenallowedtoescapefromtheinteriorofthehouse.
Cookingoutsideduringhottermonthsreducesheatloadsinside.ThisAustralianlifestyletraditiondevelopedtosuitourclimateisnotoftendirectlyconnectedtothermalcomfort.Locatebarbequesoutdoors,undercoverincloseproximitytothekitchen,withgoodaccesseitherbyserveryorscreeneddoor.Shadedbarbecueandoutdooreatingareas(insectscreenedwhererequired)facilitateoutdoorlivingandincreasedcomfort.
SleepoutsareanidealwaytoachievesleepingcomfortandcanprovidelowcostadditionalspaceforvisitorswhooftenarriveduringthehotterChristmasperiod.
Varyactivehourstomakebestuseofcomfortabletemperaturerangesatdifferenttimesoftheyear.ThesiestaregimeofmostCentralAmericancountriesisapracticallifestyleresponsetospecificclimaticconditionsthatarealsoexperiencedinhighhumidandhotdryregionsofAustralia.
Referencesandadditionalreading
Contactyourstate,territoryorlocalgovernmentforfurtherinformationonpassivedesignconsiderationsforyourclimate.www.gov.au(http://www.gov.au/)
AustralianBuildingCodesBoard(ABCB).2011.Condensationinbuildings:handbook.www.abcb.gov.au(http://www.abcb.gov.au/en/educationeventsresources/publications/abcbhandbooks.aspx)
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Beagley,S.2011.Greenhousefriendlydesignforthetropics.COOLmob,NTGovernment,Darwin.www.coolmob.org(http://coolmob.org/sustainabletropicaldesign/)
BureauofMeteorology(BOM).2011.Climateeducation:sustainableurbandesignandclimate.http://reg.bom.gov.au(http://reg.bom.gov.au/lam/climate/levelthree/cpeople/urban1.htm)
BureauofMeteorology(BOM).Windrosesforselectedlocations.www.bom.gov.au(http://www.bom.gov.au/climate/averages/wind/selection_map.shtml)
Cairnsstyledesignguide.www.cairns.qld.gov.au(http://www.cairns.qld.gov.au/buildingplanningandinfrastructure/strategiclanduseplanning/cairnsstyledesignguide)
Clark,M.2010.Designingforclimate.www.townsville.qld.gov.au(http://www.townsville.qld.gov.au/business/planning/planningscheme/Documents/Designing%20for%20Climate%20Research%20Paper.pdf)
Cole,G.2002.Residentialpassivesolardesign.Environmentdesignguide,GEN12.AustralianInstituteofArchitects,Melbourne.www.environmentdesignguide.com.au(http://www.environmentdesignguide.com.au/)
COOLmobSustainablelivingforthetropics.www.coolmob.org/design(http://coolmob.org/sustainabletropicaldesign/)
DepartmentofHousingandRegionalDevelopment.1995.Australianmodelcodeforresidentialdevelopment(AMCORD).AGPS,Canberra.www.sunshinecoast.qld.gov.au(http://www.sunshinecoast.qld.gov.au/addfiles/documents/planning/maroochy_plan/vol_pdf/qld_res_design_guideline.pdf)
Givoni,B.1995.Passiveandlowenergycoolingofbuildings.JohnWiley&Sons,Brisbane.
Hollo,N.2011.Warmhousecoolhouse:inspirationaldesignsforlowenergyhousing,2ndedn.ChoiceBooks,NewSouthPublishing,Sydney.
Hyde,R.2009.Climateresponsivedesign.FishpondAustralia.www.fishpond.com.au(http://www.fishpond.com.au/Books/ClimateResponsiveDesignRHyde/9780419209706)
Koenigsberger,O,Ingersoll,T,Mayhew,AandSzokolay,S.1974.ManualoftropicalhousingandbuildingPart1climaticdesign.LongmanLondon.
NationwideHouseEnergyRatingScheme(NatHERS).www.nathers.gov.au(http://www.nathers.gov.au/)
Prelgauskas,E.2003.Aridclimatesandenhancednaturalventilation.Environmentdesignguide,DES20.AustralianInstituteofArchitects,Melbourne.[additionalreadingnowfoundonwww.environmentdesignguide.com.au(http://www.environmentdesignguide.com.au/media/DES20.pdf)
]
Prelgauskas,E.2004.Passivecoolingbuildingsystems.Environmentdesignguide,DES59.AustralianInstituteofArchitects,Melbourne.www.environmentdesignguide.com.au(http://www.environmentdesignguide.com.au/)
QueenslandDepartmentofLocalGovernmentandPlanning.2011.Designguidefor6starenergyequivalencehousing.www.hpw.qld.gov.au(http://www.hpw.qld.gov.au/SiteCollectionDocuments/sixstardesignguideline.pdf)
QueenslandDepartmentofPublicWorks.2008.Smartandsustainablehomes.[additionalreadingnowfoundonwww.hpw.qld.gov.au(http://www.hpw.qld.gov.au/sitecollectiondocuments/smarthousingdesignobjectives08.pdf)
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Contactus(/contactus)Preface(/node/105)
Abbreviations(/abbreviations)Glossary(/glossary)
Climatezones(/node/110)Acknowledgements(/acknowledgements)
QueenslandDepartmentofPublicWorks.DesigningforQueenslandsclimate.[additionalreadingnowfoundonwww.hpw.qld.gov.au(http://www.hpw.qld.gov.au/SiteCollectionDocuments/SmartDesignQldClimate.pdf)
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ThinkBrickAustralia.Climatedesignwizard.www.thinkbrick.com.au(http://www.thickbrick.com.au/climatedesignwizard/)
TownsvilleCityCouncil.2010.CityofThuringowaPlanningSchemepolicies:ClimateresponsivedesignofhousingClimateresponsivedesignexemplars.www.townsville.qld.gov.au(http://www.townsville.qld.gov.au/business/planning/planningscheme/documents/climate%20responsive%20design%20of%20housing.pdf)
Wrigley,D.2012.Makingyourhomesustainable:aguidetoretrofitting,rev.edn.ScribePublications,Brunswick,Vic.
AuthorsPrincipalauthor:ChrisReardon
Contributingauthor:DickClarke,2013