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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]

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.

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.

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

ceilings.

Convectionproducesairmovementcapableofcoolingabuildingbutusuallyhasinsufficientairspeedtocoolpeople.

SolarchimneysSolarchimneysenhancestackventilationbyprovidingadditionalheightandwelldesignedairpassagesthatincreasetheairpressuredifferential.Warmedbysolarradiation,chimneysheattherisingairandincreasethedifferenceintemperaturebetweenincomingandoutflowingair.

Theincreaseinnaturalconvectionfromthesemeasuresenhancesthedrawofairthroughthebuilding.

Source:GreenBuilderSolarGuidelines(Residential)

Solarchimneysenhanceventilation.

EvaporativecoolingAswaterevaporatesitdrawslargeamountsofheatfromsurroundingair.Evaporationisthereforeaneffectivepassivecoolingmethod,althoughitworksbestwhenrelativehumidityislower(70%orlessduringhottestperiods)astheairhasagreatercapacitytotakeupwatervapour.

Ratesofevaporationareincreasedbyairmovement.

Pools,pondsandwaterfeaturesimmediatelyoutsidewindowsorincourtyardscanprecoolairenteringthehouse.Carefullylocatedwaterfeaturescancreateconvectivebreezes.Thesurfaceareaofwaterexposedtomovingairisalsoimportant.Fountains,mistspraysandwaterfallscanincreaseevaporationrates.

Photo:SunpowerDesign

Pondsprecoolairbeforeitentersahouse.

Mechanicalevaporativecoolersarecommonindrierclimatesandinlandareaswhererelativehumidityislow.Theyuselessenergythanrefrigeratedairconditionersandworkbetterwithdoorsandwindowsleftopen.Theirwaterconsumptioncanbeconsiderable.(seeHeatingandcooling)

EarthcouplingEarthcouplingofthermalmassprotectedfromexternaltemperatureextremes(e.g.floorslabs)cansubstantiallylowertemperaturesbyabsorbingheatasitentersthebuildingorasitisgeneratedbyhouseholdactivities.

Earthcouplingutilisescoolergroundtemperatures.

Passivelyshadedareasaroundearthcoupledslabskeepsurfacegroundtemperatureslowerduringthedayandallownighttimecooling.Poorlyshadedsurroundscanleadtoearthtemperaturesexceedinginternalcomfortlevelsinmanyareas.Inthisevent,anearthcoupledslabcanbecomeanenergyliability.

GroundandsoiltemperaturesvarythroughoutAustralia.Earthcoupledconstruction(includingslabongroundandearthcoveredorbermed)utilisesstablegroundtemperaturesatlowerdepthstoabsorbhouseholdheatgains.

PassivecoolingdesignprinciplesToachievethermalcomfortincoolingapplications,buildingenvelopesaredesignedtominimisedaytimeheatgain,maximisenighttimeheatloss,andencouragecoolbreezeaccesswhenavailable.Considerationsinclude:

designingthefloorplanandbuildingformtorespondtolocalclimateandsiteusingandpositioningthermalmasscarefullytostorecoolness,notunwantedheatchoosingclimateappropriatewindowsandglazingpositioningwindowsandopeningstoenhanceairmovementandcrossventilationshadingwindows,solarexposedwallsandroofswherepossibleinstallingandcorrectlypositioningappropriatecombinationsofbothreflectiveandbulkinsulationusingroofspacesandoutdoorlivingareasasbufferzonestolimitheatgain.

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.

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.

Source:AssociationofBuildingSustainabilityAssessors(ABSA)

Relationshipbetweensunangleandheatgain.

AirmovementandventilationDesigntomaximisebeneficialcoolingbreezesbyprovidingmultipleflowpathsandminimisingpotentialbarrierssingledepthroomsareidealinwarmerclimates.

Becausebreezescomefrommanydirectionsandcanbedeflectedordiverted,orientationtobreezedirectionislessimportantthantheactualdesignofwindowsandopeningstocollectanddirectbreezeswithinandthroughthehome.

Usecasementwindowstocatchanddeflectbreezesfromvaryingangles.

Source:DeptofEnvironmentandResourceManagement,Qld

Forbreezecollection,windowdesignismoreimportantthanorientation.

Winddoesntblowthroughabuildingitissuckedtowardsareasoflowerairpressure.Todrawthebreezethrough,uselargeropeningsontheleeward(lowpressureordownwind)sideofthehouseandsmalleropeningsonthebreezeorwindward(highpressureorupwind)side.Openingsnearthecentreofthehighpressurezonearemoreeffectivebecausepressureishighestnearthecentreofthewindwardwallanddiminishestowardtheedgesasthewindfindsotherwaystomovearoundthebuilding.

Airflowpatternandspeedfordifferentopeningareas.

Inclimatesrequiringwinterheatingtheneedforpassivesolarnorthsuninfluencestheseconsiderationsdesignersshouldstriveforabalancedapproach.

Thedesignofopeningstodirectairflowinsidethehomeisacriticalbutmuchoverlookeddesigncomponentofpassivecooling.Size,type,externalshadingandhorizontal/verticalpositionofanyopenings(doorsandwindows)iscriticalasshowninthediagramsbelow.

Source:SteveSzokolay

Airflowpatternforwindowsofdifferentopeningheight.Louvrewindowshelptovaryventilationpathsandcontrolairspeed.

Considerinstallingalouvrewindowabovedoorstoletbreezespassthroughthebuildingwhilemaintainingprivacyandsecurity.Inclimatesrequiringcoolingonly,considerplacingsimilarpanelsaboveheadheightininternalwallstoallowcrossventilationtomovethehottestair.

Positionwindows(verticallyandhorizonally)todirectairflowtotheareawhereoccupantsspendmosttime(e.g.diningtable,loungeorbed).

Inroomswhereitisnotpossibletoplacewindowsinoppositeoradjacentwallsforcrossventilation,placeprojectingfinsonthewindwardsidetocreatepositiveandnegativepressuretodrawbreezesthroughtheroom,asshowninthediagrambelow.

Usefinstodirectairflow.

Designandlocateplanting,fencesandoutbuildingstofunnelbreezesintoandthroughthebuilding,filterstrongerwindsandexcludeadversehotorcoldwinds.

Planttreesandshrubstofunnelbreezes.

Planttreesandshrubstofunnelbreezes.

InsulationInsulationiscriticaltopassivecoolingparticularlytotheroofandfloor.Windowsareoftenleftopentotakeadvantageofnaturalcoolingandwallsareeasilyshadedroofs,however,aredifficulttoshade,andfloorsareasourceofconstantheatgainthroughconductionandconvection,withonlylimitedcoolingcontributiontooffsetit.

InsulationlevelsandinstallationdetailsforeachclimatezoneareprovidedinInsulationandInsulationinstallation.Paycarefulattentiontoupanddowninsulationvaluesandchooseappropriatelyforpurposeandlocation.

Inclimatesthatrequireonlycoolingorthosewithlimitedcoolingneeds,usemultiplelayersofreflectivefoilinsulationintheroofinsteadofbulkinsulationtoreduceradiantdaytimeheatgainswhilemaximisingnighttimeheatlossthroughconductionandconvection.Thisisknownastheonewayinsulationvalve.

Reflectivefoilinsulationislessaffectedbycondensationandishighlysuitedtocoolingclimateapplicationsasitreflectsunwantedheatoutwhilenotreradiatingitin.

Roofspace

Wellventilatedroofspaces(andothernonhabitablespaces)playacriticalroleinpassivecoolingbyprovidingabufferzonebetweeninternalandexternalspacesinthemostdifficultareatoshade,theroof.

Wellventilatedroofspacesformabufferbetweeninternalandexternalareas.

Ventilatorscanreducethetemperaturedifferential(seePassiveheating)acrossceilinginsulation,increasingitseffectivenessbyasmuchas100%.Theuseoffoilinsulationandlightcolouredroofinglimitsradiantheatflowintotheroofspace.

Usecarefuldetailingtopreventcondensationfromsaturatingtheceilingandinsulation.Dewpointsformwherehumidaircomesintocontactwithacoolersurface,e.g.theundersideofroofsarkingorreflectivefoilinsulationcooledbyradiationtoaclearnightsky.(seeSealingyourhome)

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.

Source:AdaptedfromBallinger1992

Airmovementrelativetofanposition.

Fansshouldbelocatedcentrallyineachspace,oneforeachgroupingoffurniture.Anextendedlounge/diningareaneedstwofans.Inbedrooms,locatethefanclosetothecentreofthebed.Becauseairspeeddecreaseswithdistancefromthefan,positionfansovertheplaceswherepeoplespendthemosttime.(seeHeatingandcooling)

WholeofhousefansWholeofhouseorrooffansareidealforcoolingbuildings,particularlywherecrossventilationdesignisinadequate.However,theydonotcreatesufficientairspeedtocooloccupants.

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

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.

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.

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

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.

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.

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

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.

Temperateclimatescallforgoodorientation,passiveshadingandcrossventilation.

Coolandcoldclimateswhereheatingdominates(Zones7and8)Zone7requirescarefulconsiderationofcoolingneedsbecauseclimatechangemodellingindicatesthatitislikelytobeimpactedbyclimatechangemorethanmostotherzones.

Thisnecessitatesashiftfromthecurrenthighthermalmassdesignpracticestomoderateorlowmassdesignswithcarefullycalculatedglasstomassratiostoavoidsummeroverheating.Highermasssolutionsremainusefulinhigheraltitudeandcolderregionswheresignificantdiurnalrangesarelikelytocontinuetoprovidereliablecoolinginallbutextremeweatherevents.

Winterheatingremainsthepredominantneedinallbutthewarmestregionsinthesezones.Passivesolarorientationandshadingiscritical.Onsiteswherepassiveheatingorcoolingaccessislimited,considerlowmass,highinsulationsolutionswithhighlyefficientreversecycleheatpumps.Giveincreasedattentiontothedesignofhighlevelcrossventilationfornightcooling.LowUvaluedoubleglazingwithhighSHGCishighlydesirableduetoitseffectivenessinbothsummerandwinter.Useawelldesignedcombinationofreflectivefoilandbulkinsulation.Usemodestareasofglazingwiththemajorityfacingnorthwheresolaraccessisavailable.Minimisewestfacingglazing.Passiveand/oractiveshadingofallglazingisessential.

AdaptinglifestyleApplicableinallclimates,especiallyhothumidandhotdry,adaptinglifestylemeansadoptingliving,sleeping,cookingandactivitypatternsthatrespondtoandworkwiththeclimateratherthanusingmechanicalcoolingtoemulateanalternativeclimate.

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)

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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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) ]

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