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In Townsvilles climate it is essential to choose building materials that perorm well in our local conditions.

Choosing the correct materials and insulation will improve the overall thermal perormance o your home,making it more comortable and consequently less energy dependant.

Figure 1 Example o radiation.

Introduction

In our local climate, building materials should:

releaseunwantedheatquicklyoncethesunhasgoneandithasbeguntocooldowne.g.lightweightwalls;

keep out the heat during the day e.g. appropriateinsulationandcolourchoice;and

notstoreheatandreleaseitinsidethehomelongintothenighte.g.ablockwall.

This guide outlines the problem of heat transfer andhowitcanbeminimizedbychoosingtherightbuildingmaterialsandinstallinginsulationinTownsville.

Heattransferandtheprinciplesusedtoreduceitwillbediscussedinthefollowingsections:

1.HeatTransfer;2.Roofs;3.Walls;and4.Floorsandwindows.

1. Heat Transer

Thereare threemainwaysthatheatcanbe transferredinto the home:

Radiation is heat that travels fromaheat source towarm a surface (Figure 1). An example is the sunshining throughawindowdirectly heating theoorandfurniture.

Conductionisheatthattransfersthroughsolidobjects.Anexampleofthisisheatbeingtransferredfromthe

outsidesurfaceofablock(theoutsideofthehome),totheinsidesurfaceofablock(theinsideofthehome)(Figure2).

Figure 2 Example o conduction.

Convectionisheatthatiscarriedbythecirculationofliquidsorgases(Figure3).Thecirculation continuesuntilthetemperatureevensout.Anexampleofthisiswhenhotairinaroomrises,drawingcoolerairfrombelow.

Figure 3 Example o convection.

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Figure 4 A light-coloured roo reects heat and stayscooler (Photo:TCC).

Choosingwhiteforyourroofcolourorotherlightcolourssuchascream,lightbeigeandlightgreys,isoneofthecheapestandeasiestwaystoreducetheamountofheatentering the home. For existing homes, the roof cansimply bepaintedwith a reective light colour for aninstantresult.

Figure 5 A dark-coloured roo absorbs and re-radiatesheat (Photo: TCC).

FACT 1

Recent studies have shown that a light-colouredroo can have approximately 30% lower heatgain than a dark roo. Results rom a case studyin Townsville showed that ater the roo waspainted with a reective light-coloured paint

there was a signifcant reduction in the roosurace temperature and consequent ceilingspace temperature. In turn this reduced roomtemperatures which increased human comort anddecreased the need or air-conditioning (Suehrcke,Peterson and Selby, 2008).

Roof colours to avoid include: black, dark blues, darkgreens, dark greys, reds and weathered or rustinggalvanised surfaces which can get nearly as hot as ablackroof.

Steel and Tile Roos

Steel roof sheeting such as corrugated iron, will loseheatquicklyassoonasthesunstopsshiningonit.Itsphysical properties allow it to respondquickly to anychangeintemperaturewhichisbenecial,particularlyatnight,forinstantrelieffromtheheat.

Rooftiles,becauseoftheirphysicalproperties,willslowlyabsorbheatduringthedayandthenslowlyre-radiateitintothehomeatnight.Thiscanpreventthehomefromcoolingdownquicklyandinmanycasestheinsidewillremain hotter than the outdoor ambient temperature(Figure6).

Ventilate Your Roo-SpacePoorly ventilated roof-spaces get hot. Heat comingthrough the roof superheats the air in the roof-spacewhichinturnconductsheatthroughtheceilingintotheroombelow.

Figure 6 Steel roos cool o quickly whereas tiled rooscontinue to radiate heat.

The following sections will discuss the principles ofreducingheatgaininroofs,walls,oorsandwindows.

2. Roos

Theroofisthelargestsurfaceareaofthehomeandisexposedtothesunallday.Asaresult,choosingtherightbuildingmaterialsandinsulationforyourroofisessential

forachievingthedesiredclimaticperformance.

Choose Light Colours

Light colours reect heat, preventing surfaces frombecoming excessively hot. Dark-coloured roofs absorbheat which is then transferred into the home. Thus,choosing light coloursfor theroofis vital for reducingheat gain and therefore the need for air conditioning(Figure4and5).

Ifusingtilestheinclusionofreectivefoil(refertotheReectiveFoilsectionlaterinthisguide)isessentialtohelpimprovethethermalperformanceofthehome.

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Figure 9 Reective oil under the roo sheeting keepsthe roo-space cooler than i placed onthe ceiling.

FACT 2

The temperature o trapped air in the roo-space

can exceed 70oC.

Inhomeswithaventilatedroof-space,thetemperature

of the air inthe roofwillbesimilar totheoutside airtemperature.Thissimplerenewingofairreducesexcessheat transfer down through the ceiling and into thehome.

Therefore, in Townsville, which has approximately300 sunny daysper year, ventilatinga roof-space isincrediblyimportant.Ventilatingtheroof-spaceiseasyand is done by installing: rotating roof vents, solarpoweredroofventilators,roofvents,gabledventsandunsealedeaves,tonameafew.

Insulate Your Roo EectivelyInsulation is an essential component of roofs forboth climate-responsive and air-conditioned homes.Insulation can signicantly reduce theamountofheatenteringthehome.Itcanalsohelpsealinthecoolaircreated by air-conditioning. Air-conditioning is notconsideredsustainablebutwithinsulation,canbeusedmoreeffectivelytoreduceitsimpact.

The building stage is the most convenient and hencecost-effective opportunity to insulate, therefore, planaheadtogetthebestperformanceoutofyourbuilding.

Awelldesignedinsulationsystemwilloftenpayforitselfinelectricitysavingsinaslittleastwotothreeyears.

Therearetwomaintypesofinsulation:

Reective(Figure7),and

Bulk(Figure8).

Thesearediscussedinmoredetailbelow.

Reective Insulation

Reective insulation reectsheat away froma surfacepreventing95%ofinfraredradiantheatfromenteringthe space below. It is therefore highly effective atpreventing the penetration of a large percentage ofradiantheatthatwouldotherwiseenterahomethroughtheroof.

Thereareseveraltypesofreectiveinsulation:reectivefoilsheeting(sarking),multi-cellsheeting(likebubble-wrap) and expandable concertina sheeting, amongstothers.CommonlytheseproductsareknownasreectivefoillaminatesorRFL.

RFLs shouldbe installed directly underneath the roofsheetingwiththeshinysidedownandaminimum25mmairgapbetweentheroofsheetingandthefoilor the heatwillconductstraightthrough(Figure9).Thiswillreecttheheatawaybeforeithasachancetoheatuptheroof-space.AnRFLplacedontopoftheceilingalsoworksandisapplicablewhenretro-ttinginsulation.However,itisnotaseffectiveatkeepingtheheatoutasitdoesnotpreventtheroof-spacefromheatingup.

Figure 7 Example o reective insulation (Photo: TCC).

Figure 8 Example o bulk insulation (Photo: TCC).

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3. WallsInsulate All Walls Exposed to Sun

If external walls in Townsville cannot be adequatelyshaded then it is important that they are insulated.However,iftherearebudgetrestrictionsandnotallthewallscanbeinsulated,thenwest-facingwalls,whicharesubjecttothehotafternoonsun,shouldbethehighestpriority. For more inormation on the importance oshading reer to Guide 3 - Shading Out the Heat.

Reective foil insulation on its own will provide a

signicant improvement, when installed correctly,comparedtoanuninsulated,unshadedwall.Reectivefoilinwallsmustalsohavea25mmairgaptobeeffective.However,bulkandreectiveinsulationtogethercanalsobeaneffectiveoptionforair-conditionedrooms.

Use Lightweight Walls

InTownsville,thetemperaturedropthatcomeswithsunsetisarelief.Ahomeanditscomponentmaterialsshouldrespondquicklytothecoolingoutsidetemperature.Thematerialsshouldreleaseheatrapidlyratherthanstoringitandre-radiatingitbackinsidethehome.

Lightweightwallsgenerallyconsistofeitheratimberorsteelframestructurewithcladdingxedtotheframeontheoutsideandtheinside.Externally,theycantakeonavarietyoflooksdependingonthetypeofcladdingused.Somechoices include:corrugatedsteelsheeting, brecement sheets, timber weatherboard, manufacturedboards and plywood sheets (Figure 11). Plasterboardis themost commonly selected insidelining,althoughothersareavailable.

(a) During Construction

Bulk Insulation

Bulk insulation reduces the amount of heat beingtransferred into the home. It works by resisting theamount of conducted and convected heat owbetweenthehotterairintheroof-spaceandthecoolerairinsidethehome.

There are several types of bulk insulation: polyester,

wool, bubble wrap, breglass (glass wool), rock wool(spunbresofbasaltlikeglasswool),cellulosebre(paper) and polystyrene. Depending on the type ofinsulation,thesematerialsmaybesuppliedasablanket,battsorblownlooselyontotheceilingtoformalayer.

FACT 3

The level o insulation a product is able to supply isgiven as an R-value. An R-value is a measuremento the products resistance to heat ow either UP

or DOWN.In Townsville, DOWN R-values (also calledsummer R-values) are very important, particularlyor roo and ceiling spaces. Together, all o thecomponents o a roo must achieve a minimumtotal R-value o 2.7 to comply with the buildingcode o Australia.

Insulation with high DOWN and low UP R-valuesare particularly important or homes in Townsville.

There is little or noheating required in theTownsvilleregion.Theprovisionofinsulationinthebuildingfabricmustthereforebedesignedtominimiseheatowfromtheoutsidetotheinside.

Forahomewithonlyoccasionalornoair-conditioneruse,bulkinsulationisbestinstalledundertheroofsheetingas this will keep the roof-space cool and prevent hotairbeingtransferredthroughtheceilingintotheroomsbelow(Figure10).Bulkinsulationundertheroofiseasiertoinstallduringbuildingconstructionhowever,itshouldneverbecompressedasitlosesitseffectiveness.

Forhomesthatusemoreair-conditioning,thebestplacetoinstallbulk insulationison topoftheceiling(Figure10).Placinginsulationontheceilinghelpskeepthecoolairwhereitisneededsoyouarenotinadvertentlytryingtocooldowntheroomandtheentireroof-space.

Figure 10 The best location or the installation o bulkinsulation depends on how oten the housewill be air-conditioned.

InahothumidclimatesuchasTownsville,theprovisionof bulk insulationon the ceiling sheet combined withgoodventilationoftheroof-spaceisagoodcombination.Ithastheaddedbenetinthatitcanbeeasilyretro-ttedinexistinghomes.

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FACT 4

Australian Standards speciy minimum strengthsor cyclone resistance. Did you know that homeswith lightweight walls are just as cyclone resistantas homes with concrete block walls?

Figure 11 A lightweight wall, with a layer o reectiveinsulation and a rendered fnish(Photo: ecoSAVVY).

Lightweightwallsareconstructedusingacombinationofmaterials.Theyareeasierandcheapertoinsulatebecausethere is a cavity (Figure 12) between the external andtheinternalcladdingintowhichinsulationcanbettedwithouttheneedforadditionalconstructionmethods.

Figure 12 A section o a lightweight wall with both bulkand oil insulation in-between the raming.

Homes do not have to be constructed exclusively fromlightweight walls. In some cases, a combination oflightweightandmasonrywallscan bevery successful.Agoodexampleofthisiswheretheinternalwallsofahome

have been constructed from concrete blocks whilst theexternalwallsareconstructedfromlightweightmaterials.

Use Masonry with Care

Masonryisthetermgiventobuildingmaterialssuchasbricks,concrete blocks,concrete, rammedearthwalls,clayrooftiles,andsimilarbuildingmaterials.

FACT 5

Thermal Mass is a material or element in thehome that absorbs, stores and later releasesheat to great eect. Thermal mass has two mainproperties; the ability to absorb and release heat,known as Thermal Lag and its capacity to store

heat, known as Volumetric Heat Capacity.

Masonrythatisexposedtoa hotenvironmentabsorbsheat and then slowly releases it over many hours atnight.Thisresultsinhomesthatareslightlycoolerinthemiddleof theday, butconsistentlywarmer in the lateafternoonsandeveningwhenmanyofusareathome.Asaresult,masonryhomesgenerallyneedair-conditioningtoremaincomfortableduringthosetimes.

For homes in the tropics,masonrymustbeusedwithcare.Ifmasonryistobeusedasabuildingmaterialitmustbeeithershaded,oralternatively,insulated(Figure

13and14).

Figure 13 Masonry walls can be prevented rom heatingup by insulation (let) or shading (right).An example o which is a pergola withlandscaping over it.

FACT 6

In Townsville, concrete block walls have becomethe preerred building method. Reasons or thisinclude availability, cost, speed o erection andbuilding covenants but do not include climaticperormance.

However, this may change over time as new buildingregulations are introduced that require our homesto perorm better in our climate.

To insulate a concrete blockwall, a frame is attachedtoeither the outsideor the inside of the wall therebyprovidingaspacefortheinsulation.Claddingcanthenbexedtotheframetocoverandprotecttheinsulation(Figure14).Insulatingtheoutsideisgenerallypreferredas this prevents the block wall from heating up andre-radiating heat. Insulating the insideof a blockwallmaybelimitedtobulkinsulationforanykindofthermalimprovement. Installing foil in-between a masonryblockwall andan internal wall liningwill not improveperformance.

(b) Ater Construction

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Tinted Glass

Usingtintedglasscanhelpreduceglareandheattransferthroughwindows(Figure15).

Figure 15 Less heat passes through tinted glass.

FACT 9

Double glazed windows will stop the outsideheat rom coming into a cool or air-conditionedroom. However, they must be completely shadedto prevent the suns rays penetrating through andheating the room.

Whatyourhomeismadeofwillhaveadirecteffectonhow well it performs in Townsvilles tropical climate.Lightweightandlight-colouredmaterialswillachievethebestoverallthermalperformanceforyourhome.

Planning ServicesSpecial Projects Unit

Ph:47279000Fax:47279052www.townsville.qld.gov.au

CONTACT

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FACT 8

I you are planning on air-conditioning your homeit is recommended that both concrete and timbersuspended oors in tropical regions are insulatedwith a minimum R1.0 insulation.

Raised Timber

Naturallyventilatedhomeswithraisedtimberoorscanbenetfromnothavinganyinsulationundertheoortoenhancetheirabilitytocoolthehomeallyearround.Thiscoolingisespeciallybenecialinthesummer.

However, once residents are used to the highertemperaturesofTownsville,theweeksduringmid-wintercan feelquitecold.In this case, insulationunderneatharaisedtimberoormaybedesired.However,thiswillreducetheeffectsofventilatedcoolingduringsummer.

4. Floors and WindowsMasonry Floors

Masonry or concrete slab oors can be benecial inTownsville when they are kept out of the sun. Theyare slow to respond to temperature change, which isadvantageousbecausetheykeeptheircoollonger.

Because masonry materials keep a fairly constanttemperaturewhenintheshade,orincontactwiththeground,theywilloftenprovideapositivecoolingeffect;particularly compared to the midday air temperature.

Thesematerialswillbecomparativelycooltothetouch,allowingyoutobenetbyfeelingcoolerintheheat.

This can also be applied to fully shaded,masonry orstoneinternalwalls.

Thereareseveralproductsonthemarketbasedeitheronreectivitylmsappliedtotheglasssurfaceoraspecialinter-layerappliedtolaminatedglass.

Shadingisstillthemosteffectivemeansofreducingheatgainintoahomeregardlessofglasstype.However,tinted

andhighperformancetypesofglasscanbeparticularlybenecialforwindowsontheeastorwestofthehouseorwindowsthatmightotherwisebedifculttoshade.

Figure 14 Wall cross-section showing insulation on theoutside o the block wall.

There are many alternatives to traditional concreteblocks.Onebuilding alternative isAutoclavedAerated

Concrete(AAC).Thisproductislighterandmoreenergy-efcientcomparedtoregularconcreteblocks.

FACT 7

One night, go out and put your hand on any concretesurace that has been in the sun; i it is still warmit is still radiating heat. This makes your home, andthe area around it, hotter.