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Center for the Built Environment
UC Berkeley
Peer Reviewed
Title:
Shading and Cooling: Impacts of Solar Control and Windows on Indoor Airflow
Author:
Hildebrand, Penapa Wankaeo
Publication Date:
01-30-2012
Series:
Envelope Systems
Permalink:https://escholarship.org/uc/item/5087z1zd
Keywords:
indoor air flow, air velocity, thermal comfort, natural ventilation, solar control, passive solar ,windows, overhangs
Abstract:
In a suitable climate, winddriven ventilative cooling has the potential to lowerdependenceon fossil fuels in both new construction and building renovations by minimizing theamount ofmechanical cooling energy used. Utilizing exterior shading with windows significantlyreduces theneed for cooling by lowering solar heat gain, thus increasing the chances that lowenergycoolingstrategies, like natural ventilation, will work. While the main function of exteriorshading is to
block direct sun, such projections also directly affect the incoming airflow throughopen windows,interior daylighting, and the buildings form and faade. Thus, exterior shadingis likely to obstructairflow into the building3. Screenlike shading systems mounted in front ofoperable windows areparticularly susceptible to this effect.
Given the desire to shade and ventilate naturally, what is the affect of screen shadingsystemson the indoor airflow in the occupied zone? What combination of window and shademinimizesobstruction to, or perhaps even enhances, airflow?
This thesis examines these questions via wind tunnel tests of a lowrise classroomlikebuildingmodel with interchangeable shades and windows. This first chapter introduces thecore issuesinvolved in this study: the tropical climate, tropical vernacular and modernbuildings, screen shadesin contemporary architecture, and classroom buildings.
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ShadingandCooling:ImpactsofSolarControlandWindowsonIndoorAirflow
by
PenapaWankaeoHildebrand
Athesissubmittedinpartialsatisfactionofthe
requirementsforthedegreeof
MasterofArchitecture
inthe
GraduateDivision
ofthe
University
of
California,
Berkeley
Committeeincharge:
ProfessorM.SusanUbbelohde,Chair
ProfessorCharlesC.Benton
ProfessorPeterC.Bosselmann
Spring2011
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ContentsTable
of
Contents............................................................................................................................. i
List
of
Symbols................................................................................................................................ iii
CHAPTER1:INTRODUCTION/ARCHITECTUREINTHETROPICALCLIMATE ...............................1
1.1
TheTropical
Context
..................................................................................................
2
1.2 TropicalVernacularandModernBuildings............................................................... 4
1.3 ScreenShadesinContemporaryArchitecture.......................................................... 7
1.4 Classrooms .............................................................................................................. 11
CHAPTER
2:
VENTILATION
2.1 TheRoleofVentilationinBuildings......................................................................... 15
2.2 ThermalComfortStandards.................................................................................... 18
2.3 Objectives................................................................................................................ 20
2.4
Approach
..................................................................................................................
21
CHAPTER
3:
PREVIOUS
RESEARCH
3.1 ExistingDesignGuidelines ...................................................................................... 23
3.2 Regionspecificguidelines........................................................................................ 25
3.3 MethodsofTestingWinddrivenNaturalVentilationinBuildingDesign...............25
3.4 AcademicPapersandParametricWindTunnelVentilationStudies.......................29
3.4.1 Consolidationoftheresultsofmultiplewindtunneltests
3.4.2 BoundaryLayerandSiteDensity
3.4.3 Buildingmassingandshape
3.4.4
Roomdepthandproportions
3.4.5 OpeningSizeandLocation
3.4.6 WindowGeometryandDetails
3.4.7 ExteriorProjectionsandShading(OverhangsandWingWalls)
CHAPTER
4:
EXPERIMENTAL
METHODS
4.1 Testingconditions:BoundaryLayerWindTunnel&DataAcquisition...................37
4.2 BuildingModelDescription..................................................................................... 38
4.3 VelocityMeasurements........................................................................................... 39
4.4
FlowVisualization
....................................................................................................
41
4.5 SelectionofShadingDevicesandWindowTypes...................................................41
CHAPTER
5:
RESULTS ................................................................................................................... 45
5.1 WindTunnelTestResults........................................................................................ 45
5.1.1 Outletopeningtests............................................................................................. 48
5.1.2 Inletwindowtests................................................................................................. 53
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5.1.2.1 Awningwindowtest.......................................................................................... 54
5.1.2.2 Casementwindowtest...................................................................................... 56
5.1.2.3 Doublehungwindowtest................................................................................. 58
5.1.3 ShadeScreenTests............................................................................................... 60
5.1.3.1
Louver
Screen
Test
............................................................................................
61
5.1.3.2 PerforatedPanelTest ....................................................................................... 63
5.1.4 ShadeandWindowCombinedTests.................................................................... 65
5.1.4.1 LouverScreenandAwningWindow.................................................................. 68
5.1.4.2 LouverScreenandDoublehungWindow.........................................................70
5.1.4.3 PerforatedPanelwithAwningWindow............................................................72
5.1.4.4 PerforatedPanelwithDoublehungWindow...................................................74
5.2 ExploringthePotentialforThermalComfort .........................................................76
5.3 LimitationsoftheMethods..................................................................................... 81
CHAPTER
6:
DISCUSSION
6.1 Whatcombinationsofshadescreensandwindowtypescreateuniformlyhigh
velocityratiosacrosstheoccupiedzone?...............................................................82
6.2 Howdoexteriorshadescreensinfrontofoperablewindowsaffectairflowand
shouldtheybeusedifnaturalventilationisagoal?Whatwindowtypeismost
compatiblewithascreenshadeintermsofoccupantcooling? ............................82
6.3 Whatcharacteristicoftheshadescreengeometryreducesairvelocity?Howdo
thedifferenttypestestedcompareintermsofchangingthevelocityofairflow? 83
6.4 Howdoestheairflowvarywithwindowtype? ......................................................86
6.5
Givenacombination
of
shades
and
windows
that
effectively
promotes
air
movementintheoccupiedzone,atwhattimesiswinddrivencoolingacceptable
forthermalcomfort?Whatfactorscanexpandtheuseofnaturalcoolingina
classroomsetting?................................................................................................... 91
CHAPTER
7:
CONCLUSIONS
7.1 Conclusions.............................................................................................................. 92
7.2 SuggestionsforFutureWork................................................................................... 93
BIBLIOGRAPHY..............................................................................................................................
94
APPENDIX
A:
THERMAL
COMFORT
EXPLORATION
TABLE..........................................................95
APPENDIXB:SENSORCALIBRATION..................................................................................................
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ListofSymbols
VPLAN = meanspatialvelocityratioinplan,ND
SPLAN = standarddeviationofthevelocityratioinplan,ND
VSECT = meanspatialvelocityratioinsection,ND
SSECT = standarddeviationofthevelocityratiosinsection,ND
CSV = coefficientofspatialvariation,ND
Vi = meaninteriorvelocitylocationi,m/s
Vref = meanreferencevelocitylocation,takenintheunobstructedfreestreamupwind
ofthemodelat1.1mseatedheadheight(modelscale)orabovethemodelfloor
level,or5abovethewindtunnelfloor.
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1
CHAPTER1 INTRODUCTION
Throughmostofhistory,naturalventilationwasacommonlyusedpassivecooling
strategyinbuildingdesign.Today,inalargepartofthedevelopingworld,naturalventilationis
stillamainformofcooling.Thisisalsothecaseformanybuildingsintendedtobeenergy
conscious.Itiscommonformanybuildingstodaytoheavilyrelyonairconditioningtoachieve
thermalacceptability,ataskthestructureitselfonceperformed.Reinforcingwhatmany
intuitivelyalreadyknow,research1andrecentthermalcomfortstandards
2agreethatincreasing
airflowimprovesthermalcomfortinwarm,humidenvironments.
Inasuitableclimate,winddrivenventilativecoolinghasthepotentialtolower
dependenceonfossilfuelsinbothnewconstructionandbuildingrenovationsbyminimizingthe
amountofmechanicalcoolingenergyused.Utilizingexteriorshadingwithwindowssignificantly
reducestheneedforcoolingbyloweringsolarheatgain,thusincreasingthechancesthatlow
energycoolingstrategies,likenaturalventilation,willwork.Whilethemainfunctionofexterior
shadingistoblockdirectsun,suchprojectionsalsodirectlyaffecttheincomingairflowthrough
openwindows,interiordaylighting,andthebuildingsformandfaade.Thus,exteriorshading
islikelytoobstructairflowintothebuilding3.Screenlikeshadingsystemsmountedinfrontof
operablewindowsareparticularlysusceptibletothiseffect.
Giventhedesiretoshadeandventilatenaturally,whatistheaffectofscreenshading
systemsontheindoorairflowintheoccupiedzone?Whatcombinationofwindowandshade
minimizesobstructionto,orperhapsevenenhances,airflow?
1Givoni1962,Chand1974,Arens1986.2ASHRAE552010,section5.2.3.3Sobin1981.Aynsley1979.Smith1970.
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Thisthesisexaminesthesequestionsviawindtunneltestsofalowriseclassroomlike
buildingmodelwithinterchangeableshadesandwindows.Thisfirstchapterintroducesthe
coreissuesinvolvedinthisstudy:thetropicalclimate,tropicalvernacularandmodern
buildings,screenshadesincontemporaryarchitecture,andclassroombuildings.
1.1 THETROPICALCONTEXT
Beforethemid20thCentury,buildingsinthetropicalclimatesofthisstudydidnotuse
airconditioningtocooltheirinteriors.Incontrastwiththenaturallyventilatedvernacular,
contemporarytropicalcommercialandinstitutionalbuildingshavebecometaller,mechanically
cooledandglazed.Today,airconditioningisusedthroughoutcommercial,institutionaland
someschoolandresidentialbuildingsinmuchofthetropics.Thesebuildingsareoften
conditionedtothesamethermalcomfortstandardsasthoseusedintemperateclimatesand
thusconsumeanenormousamountofelectricityintheprocess.Suchthermalconditionshave
becomecommonplaceinautomobiles,shopsandothertransientspaces.
Inadditiontorequiringmoreelectricalpowertoday,airconditioningseemsto
conditionpeopletorequiremoreofitinthefuture,byloweringourabilitytotoleratehigher
temperatures.4Theaddictiontomechanicalcoolingseemsinsatiable.Isthereawaytoundo
someofthisdependenceonfossilfuels?Cooledairneedssealedspaces;sealedspacesisolate
usfromtheoutsideworld.Overtime,thisisolationmakestheoutdoorsseemaforeignplace.
Whilethisdissociationmaybedesirableforaperformancehall,itisarguablylesscrucialfor
classrooms,offices,andotherdailyfunctions.Mightreintroducingnaturalventilationindoors
restoretheawarenessthatairconditioningtookaway?
4deDearandBrager,2001andBusch,1991.
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Figure1.Mapoftropicalandsubtropicalzonesintheworld.(HindrichsandDaniels.2007)
Thetropicalandsubtropicalregionstakeupaverysignificantportionofearthsland
massandpopulation.Becauseoftheangleatwhichthesunstrikestheearth,mostareaswithin
thetropicsarehotyearround.AccordingtoWikipedia,Unliketheextratropics[or
subtropics],wheretherearestrongvariationsindaylength,andhence[seasonal]temperature
tropicaltemperaturesremainrelativelyconstantthroughouttheyearandseasonalvariations
aredominatedbyprecipitation.5Therearethreetypesoftropicalclimates,basedon
variationsinprecipitation:thetropicalrainforestclimate(dominatedbylowpressure),the
tropicalmonsoonclimate,andthetropicalwetanddry(orsavanna)climate.Forthesakeof
simplifyingthestudy,theclimateselectedisthatofBangkok,Thailand,at13.75Nlatitude.
Bangkoksclimateisacombinationbetweentropicalmonsoonandtropicalsavannah.This
climateisgenerallymarkedbythreeseasons,withthestartandendofeachseasonvarying
slightlyintheNorthernHemispheretropics.Thesummer(orthehottestseason)tendstooccur
aroundMarchthroughJune,withhighdrybulbtemperaturesandmoderatetohighhumidity.
5http://en.wikipedia.org/wiki/Tropical_climate
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Themonsoonseason,fromaboutJuneorJulythroughOctober,isverywarmandhumid,with
relativehumidityfrequentlyapproaching100%,makingevaporativecoolingnearlyimpossible.
Whenthereisprecipitation,temperaturesdropslightly,butquicklyriseagainoncetherain
stops.Skiesduringthemonsoonperiodtendtobecloudyanddiurnaltemperatureswingsare
smallerduringthisseason.Thetropicalwinterseasonismarkedbywarmtemperatureswith
lowerhumiditythantheotherseasons.Diurnaltemperaturestendtovarythemostduring
winter.
1.2 TROPICALBUILDINGS
Onepurposeofbuildingsistoshelterpeoplefromtheelements:sun,windandrain.
Throughoutthecenturies,thepeoplesofthetropics,havebuilt,adjusted,andperfectedan
architecturethat,besidesprovidingadequateshelterfromtheelements,wasshapedtotheir
customsandwassustainedbynaturallyavailableresources.Thisisreflectedinthedistinct
featuresofthevernaculararchitectureoftropicalregions.(Ingeneral,thesolutionsthathave
prevailedarethosethatbestservemultiplepurposes.)
Intheseregions,traditionalhouseswereoftenraisedfromthegroundinordertocatch
thestrongerbreezeshigherup,toreducemoisturemigrationfromthesoil,andtoprovide
protectionfromseasonalflooding.Thespaceunderneaththehousewasusedasashaded
outdoorroom.
Sometimesitwaswithhighpitchedgablesandlargeeavesthattropicalarchitecture
respondedtotheabundantrains:rainwaterflowedquicklyoffthesurfaceoftheroofandthis
protectedtheinteriorfromleaks. Thedeepeavesalsokeptthedriplinefurtherawayfromthe
house,protectingoftenporouswallsfromrain.
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T
narrowf
possible
outdoor
addition
shadedt
I
directly
roofsth
vernacul
includes
bringing
cleardif
glassto
hehighroo
loorplates
fornatural
spaceslike
lrooms.G
heexterior
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ar,thereis
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erentiation
eparateins
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entilationa
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ide.
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airtorise
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atahighan
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keepthein
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teriorscool.
lsomadeit
atitudes,
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.Inthis
indowsof
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buildings
gure2. Left:st
tticeAgraFort,
ra,India.(pho
thor)Right:
oodenlattice
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ovenbamboo
nstructioninL
abang,Laos.
omsanuk,2004
The
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)
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Figure3.Left:Arareuseofstaggeredfixedpaneglazedwindowsallowforthepassagelightandairwhileblockingrain. Wat
PhraKaeoMuseum.(photobyauthor).Middle:dualactionwindowswithpanelsashesthatcanopenlikeadoublecasement
orlikeawningwindowsorBahamashuttersatLetsSeaHuaHinResort,Thailand.Windowsashes,whenpresentinthe
tropicalvernacular,tendtobesolidorslattedshutters.(photobySitthaSukkasi).Right:Overhangsandsolidpanelcasement
windowsinHappyHausinQueensland,Australia6
Theintroductionofglassinthecolonialeraseparatedtheinsideandtheoutsidethat
hadnotbeensoclearlydistinctbefore,asseeninexamplesoftraditionalThaiarchitecture. But
colonialarchitecturealsoobserveditsneighboringtraditionalhousesandadaptedsomeofits
elements.Thewalls,nowmadeoutofbrick,furtherseparatedtheoutsidefromtheinside
environment;thethermallymassivematerialsofbrickandconcreteretaindaytimeheatwell
intotheevening.
Largerwindowsthatcouldstillbeclosedwithshutters,createdanewcoolinterior
space. Verandahsandgallerieswerealsoadaptedtobrick,buttheykeptfunctioningasan
exteriorshadedroomthatalsoprotectedthewallsfromthesun,loweringtheexteriorheat
loads. Thechangeinmaterialscreatedanewcontrolledenvironment,slowertorespondtothe
exteriorconditionsthanthelocalarchitecture.
6Jordana,Sebastian."HappyHaus/DonovanHill"29Jun2010.ArchDaily.Accessed10Dec2010.
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1.3 SHADESCREENSINCONTEMPORARYARCHITECTURE
Onceairconditioningbecamemorecommon,buildingsincorporatedmoreglass,bothin
largerwindowsandcurtainwallsystems,anddeeperfloorplates,sinceproximitytowindows
wasnolongerrequiredtolightandcool.Withtheintroductionofglassseparatinginsideand
outside,thedifferencebetweenwindowsashandshadeclearlyemerges.Withoutsufficient
shadingprotectionfromthesun,theseinternalloaddominatedbuildingsquicklyoverheatand
requireevenmoreenergytocool.Somearchitectsandengineersacknowledgedtheallglass
dilemmaandincorporatedexternalshadingintobuildingdesigns.Startinginthe1950s,there
wasanupsurgeinresearchandpublicationsaroundclimateadaptivedesignandmaximizing
passiveheatingandcooling.PublicationsforarchitectsincludedDesignwithClimate(Olgyay
andOlgyay1963),SolarControlandShadingDevices(Olgyay1957),andTropicalArchitecturein
theDryandHumidZones(DrewandFry1964). Beforetheenergyimplicationsoftheallglass
buildingwerethoughttobeimportant,unprotectedglassstructuresbeganappearingin
tropicalclimates.Theyarestillbeingbuilttoday,thoughwithmoreadvancedglass
technologies.
Figure5.VarioustypesofshadingfromFryeandDrew. Figure4.TheIIMDormitoriesinAhmedabad,India(Louis
Kahn)weredesignedtobeprotectedfromthesunand
permeabletothewind.Imagesfromand
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Anincreasedawarenessofenergydepletion,fuelpricerise,andclimatechangehas
broughtaboutaninterestinloweringallenergyuseandbuildingenergyuseinparticular.Low
energycoolingstrategies,likenaturalventilation,requirecarefulloadcontrolandblockingheat
gainfromthestructure,windowsandinteriors.Intropicalbuildings,minimizingsolarheatgain
isdoneintwomainways:firstbyinsulatingexteriorwalls,(thusrestrictingtheinteriorsurfaces
fromradiatingheattowardtheoccupiedareas),andsecondbyshadingopeningsfromdirect
sunpenetration.Thefirstmethodinvolvesinsulativeandradiantbarriersinthebuilding
enclosure;thoughimportantfortheclimate,thisisoutsidethescopeofthepresentstudy.The
secondmethod shadingopenings isachievedbyblockingdirectsunfromenteringthe
occupiedspacewithsomesortofinteriororexteriorshadingdevice.
Externalshadingcanblocksignificantlymoresolarheat7andtendstobeamorevisually
prominentpartofthearchitecture,ascomparedwithinternalshades.Shieldingthebuilding
anditsoccupantsfromthesunisespeciallyrelevantinclimateswhereourbodieseasily
overheat,asinthetropical,lowlatitudeenvironmentsofinterestinthisstudy.Intheseregions,
thismeanshighangledsunfromthenorthandsouthportionsofabuildingandlowerangled
sunfromtheeastandwest.Formsofexternalshadingincludehorizontaldevices,like
overhangs,andverticaldevices,likeverticalfinsorwingwalls,8aswellasarchitecturalfeatures
suchaslargeroofs,loggiasandothervolumetricforms.
Ascan
be
seen,
many
forms
ofexterior
shading
have
been
employed
throughout
the
centuries.Whilescreenshadeshavealsobeenutilizedhistorically,suchsystemshavebecomea
7AccordingtoafieldtestbyLawrenceBerkeleyNationalLaboratory,coolingloadswerereducedby77%with
exteriorVenetianblindsascomparedtoconventionalinteriorVenetianblindsunderthesameconditions.Lee,
2009.InnovativeFaadeSystemsforLowenergyCommercialBuildings.(askpermission)8SolarControlandShadingDevicesbyOlgyayandOlgyay,1976(page88)isacomprehensivesourceforexterior
shading.
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clearvis
building
(Morpho
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Figure10.ToulouCollectiveHousinginNanhai,Guandong.URBANUSArchitecture&Design,Inc.
Figure11.Examplesoflow andmidrisebuildingsinthetropicalclimateofBrisbane,Australia(DonovanHill). left,W4
Apartments.Right,CornwallApartments.
Figure9.Multiple
exteriorshadingtypesin
MoulmeinRise
ResidentialBuilding,
SingaporebyWOHA
Architects.left:south
faade.middle:north
faade.right:
view
out
thenorthfaade.Images
fromand
Figure8.Rectorate
OfficeBuilding.
Hauvette&Associs.
Cayenne,French
Guyana.Imagesfrom
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Figure12.NishorgoOirobotNatureInterpretationCentre.Teknaf,Bangladesh.VittiSthapatiBrindoandEhsanKhan,2008.
1.4 CLASSROOMS
Thebuildingofinterestinthisstudyisthelowriseschoolbuilding,andspecificallythe
classroomspace.Classroomsaregoodcandidatesforstudy;thesettingtendstobeuniformlyand
denselyoccupiedwithanumberofstudentsseatedatdesks.Exceptforclothingadjustments,students
donottypicallyhavedirectcontrolovertheirthermalcomfortinclassrooms.Thoughitisparticularly
challengingtoevenlycoolwithwinddrivenventilationformultipleoccupants,thechallengesassociated
withthistaskmayhavearoleininformingnaturalventilationstrategiesinothernondomesticspace
types,suchasopenplanoffices,smallretailandclinicsinlowrisebuildings.
Twomainrequirementsbracketedthescaleatwhichtosizethemodelinthisstudy:indoorair
movementstudieswarrantalargermodelforvisualizingtheinterior;tallerbuildingsrequiresmaller
models(oralargerwindtunnel)soasnottoblockmorethan510%ofthewindtunnelcrosssectional
Figure13.ElCamion
Restaurant.
Llona+Zamora
arquitectos+Fernando
Mosquera.Villael
Salvador,Lima,
Peru.
Imagesfrom
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area.Fromthepointofviewofwindtunnelstudiesfornaturalventilation,lowrisebuildingsseemed
idealfortestingdetailedfaadecomponentssuchasexteriorshadesandwindows.
Openplanspaces(likeclassroomsorsomeoffices)areparticularlydesirablefromawinddriven
ventilationpointofviewsincetherearefewobstructions.Intermsofventilative(convective)cooling,it
isimportantthatfurnitureobstructaslittleaspossibleinthefirsttwelveinches(30cm)abovethefloor.
Besidesobstructingairflow,furnishingsandfinisheslikeseatsalsoaddtothethermalinsulationatthe
occupantsbodies;conductiveorbreathableseatselectioncanhelptoremoveheatfromthebody.
Thoughthetropicalvernacularbuildingsmentionedintheprevioussectiontendtobehousesof
lightwoodconstruction,thehistoricalbeginningsofformaleducationinThailandexistedintheBuddhist
temples,whichtypicallyhadmassive(sometimes30thick)loadbearingwalls,shading,andground
contacts9.Oftenthemainhallwassurroundedonallsidesbyverandas.Templeswereoneofthefew
nondomesticstructureswhereagroupofpeoplewouldregularlygatherforprolongedperiodsoftime.
Todaymostclassroombuildingsareoneroomdeepconcreteandmasonryconstruction.Itiscommon
forstudentstonotwearshoesintheclassroom,furtherfacilitatingheattransferthroughtheirsocks.
Lowriseschoolbuildingshaveexistedforalongtimeandarelikelytocontinuetobebuiltand
retrofittedinthefuture.Fromschoolhousestoschoolbuildings,classroomshaveahistoryofhaving
narrow(1roomdeep)plans,asitiscommonforthemtobedesignedtoaccesslightandair.Lowrise
buildingsingeneralalsoofferanumberofdistinctiveproperties.Suchbuildingsarecommonwithincity
9Sresthaputra,2003.
Figure14.
Plan
and
sectionofclassroom
model.
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centersa
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Figure18.TransitionalSchool,Jacmel,Haiti.18Nlatitude.JohnRyanandPlanInternational,2010.(JohnRyan)
Figure19.PrimarySchool,Gando,Tenkodogo,BurnikaFaso.11.5NLatitude.DibdoFrancisKr,2001.(FrancisKr
Openarchitecturenetwork.orgAccessed5January2011)
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CHAPTER2 VENTILATION
2.1 THEROLEOFVENTILATIONINBUILDINGS
Intropical,lowlatituderegions,minimizingheatgainallowsnaturalventilationand
otherlowenergycoolingstrategiestowork.Naturalventilationprovidesmultipleservices:it
removesheataccumulationinthebuildingstructure(600CFM)11;itcoolsthespaceby
replacingwarmairwithcoolerair(300CFM).Inaddition,theairmovementonhumanskin
enhancesbodilycooling(300CFM);anditprovidesairforbreathing(roughly10CFM). The
typeofcoolingthatispossibleisalsoafunctionoftheamountofwindavailableandthediurnal
temperatureranges(forstructuralcooling)inaparticularsite.Whiletheprimarypurposeof
naturalventilationinthisstudyisoccupantcooling,theindirectformscoolingoutsidethe
scopeofthisstudyareimportanttoacknowledge.
STRUCTURALCOOLING.Structuralcoolingreferstotheremovalofaccumulatedheatwithinthe
buildingmassattimeswhenoutdoortemperaturesarebelowthecomfortzone;itisdirectly
relatedtothethermalstoragecapacityofthebuildingandtheexposureofthermallymassive
elementstoairflow.Areasbeyondtheoccupiedzonenearceilings,wallsandexposedfloors
tendtobeimportantforindoorspaceandstructuralcooling.Structuralcoolingislesseffective
wherewidediurnaltemperaturerangesarenotsufficient,asisthecaseduringthetropical
monsoonorsummerseasons.Thoughstructuralcoolingisnotaprimarypurposeofnatural
ventilationinthisstudy,itmayhavearoleinthetropicalsavannahclimate.
SPACECOOLING.Occupiedspacesaccumulateheatfromlighting,people,equipmentsolarand
envelopeloads,whichincreasestheambientairtemperatureovertime.Spacecoolingrefersto
11Brown,G,andUniversityofOregon.;NorthwestEnergyEfficiencyAlliance.;SeattleCityLight.2004.Natural
ventilationinnorthwestbuildings.EugeneOr.:UniversityofOregon.P.11
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thereplacementofthiswarmairwithcooleroutsideair.Balancinglowsolargainsand
daylightingareverymuchrelatedtothetypeofshadingused,asbothdirectsunandelectric
lightingcontributetothesethermalloads.Spacecoolingisanindirectformofoccupantcooling
andisnotaprimarypurposeofnaturalventilationinthisstudy.
BREATHING.Itwouldbedifficulttoadequatelydiscusstheroleofnaturalventilationin
buildingswithoutfirstacknowledgingitsroleinourbreathing.Respirationisaminorformof
bodilycoolingandabiologicalrequirement.Whiletheamountofairrequiredforbreathingis
muchlessthanthatforcooling,outsideairhasotheramenities.Unlikerecirculatedindoorair,
outdoorairismorediluted,dynamicinspeedandtemperatureandevencarriessoundand
smell.Outsideairisreflectiveofmicroclimate,topography,geographyandotherconditions12
aroundthegivensite.Whenwegooutsideforair,webecomecorporeallyawareofourbodies
inthesurroundings.Whenoutsideaircomesinside,trancesofthisconnectionarelikelyto
follow.
OCCUPANTCOOLING.Thermalcomfortiselusivelycomplextoquantify.Traditionalcomfort
models(i.e.Fanger)includedsixquantifiablevariables:thetwopersonalvariablesofclothing
levelandactivitylevel,andthefourenvironmentalvariablesofairtemperature,radiant
temperature,airvelocityandhumidity.Variableshardertoquantifythathavebeenshownalso
influencethermalcomfortincludeclimaticadaptation,thermalpreferenceandpersonal
control
13
.
12Arens,1985.
13Whenthermalcontroloccursthroughopeningandclosingwindows,theinteractionbetweentheuserandthe
buildingencouragestheoccupanttobeanactiveparticipantinthespace.Thisoccupantbuildinginteraction
visuallyactivatesthefaadeforcomfort.
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Aspreviouslystated,occupantcoolingistheprimarypurposeofnaturalventilationin
thisstudy.Airmovementworkstocoolthehumanbodyinanumberofways:firstviathe
evaporationofsweatfromtheskin,secondbyconvectivelyreplacingthewarmerairnearthe
skinwithcoolerairandlastbyreplacingwarmexpiredairwithcoolerinspiredair.
Therearelimitationsandcaveatstotheeffectivenessofairmovementforthermal
comfort:evaporativecoolingislesseffectivewhenthehumidityishigher;convectivecoolingis
noteffectivewhentheairtemperatureiswarmerthanbodytemperature;themaximum
allowableairspeedatthewarmhumidendofthecomfortzonedependsonoccupant
preferenceandactivity.Findingsfromrecentresearchandpreviousstudies14suggestthatin
bothairconditionedandnaturallyventilatedbuildings,mostoccupantsprefertohavemoreair
movementandveryfewwantless.Howcanthisfindingapplytothedesignofwindowsand
shades?
Whileitispossiblefornaturalventilationtodirectlycooloccupants,thisscenariois
oftenmoreeffectiveforoccupantsclosertothewindowthanforthosewhoarefurtheraway.
Whenthemodeofthermalcontroloccursthroughtheopeningandclosingofwindows,the
requiredinteractionbetweentheuserandthebuildingencouragestheoccupanttobean
activeparticipantinthespace.Thearchitecturebecomesvisuallyrelatedtothermalcomfort
overtimeviathisoccupantbuildinginteraction.Provisionforoccupantcontrolhasalsobeen
shownto
expand
the
zone
ofthermal
comfort.
At
the
warm,
humid
end
ofthe
comfort
zone,
themaximumallowableairspeeddependsonoccupantpreferenceandexpectations.15
14Arens,E.,Turner,S.,Zhang,H.,&Paliaga,G.2009.MovingAirforComfort.
15ASHRAE552010,section5.2.3.Thisstandardalsostipulatesthattherequiredairspeedforlight,primarily
sedentaryactivitiesmaynotbehigherthan0.8m/s.Whenunderlocalcontroloftheaffectedoccupants,theair
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Figure20.Compoundwindowswithmultipleoperationtypeswithinthesameopening.Leftandmiddle,BoydEducational
Center,GlennMurcutt,2005.34.8Slatitude.Illaroo,NSW,Australia.ImagefromDahl,2010.
2.2 THERMALCOMFORTSTANDARDS
BuildingdesignersusethermalcomfortstandardssuchasASHRAEStandard55201016,
ISO773017
andEN/DIN15251200818todesignbuildingsforhumanoccupation.These
standardsestablishspecificcriteriaforacceptablethermalenvironmentsincludingallowable
rangesforairtemperature,radianttemperature,humidityandairspeeds.Inadditiontothe
narrowlydefined,laboratorybasedresultsonwhichtheywereoriginallybased,thestandards
havecometoincorporatevariousadaptivemodelsforthermalcomfort,whicharemostly
basedonfieldstudies19.Thatis,thestandardsnowrecognizethatthermalcomfortand
preferencescandifferforpeopleofdifferentclimatesandhabits.ASHRAE55wasrecently
modifiedtoexpandtheallowablerangeofairspeedsinneutraltowarmconditions.20Thisis
importanttonotewhendiscussingwhetherornotnaturalventilationisadequateinproviding
speedmaybeashighas1.2m/s,thoughitisnotexplicitlystated.Thestandardnotesthatthesefiguresare
conservativeforactivitiesabove1.3metsandforclothinginsulationlessthan0.5clo.16ThermalEnvironmentalConditionsforHumanOccupancybytheAmericanSocietyofHeatingRefrigerationand
Air conditioningEngineers17ErgonomicsoftheThermalEnvironmentbytheInternationalStandardsAssociation
18IndoorenvironmentalInputParametersforDesignandAssessmentofEnergyPerformanceofBuildings
addressingIndoorAirQuality,ThermalEnvironment,LightingandAcoustics.19deDearandBrager2002.Rajaetal2001.Kwok,1997.Busch1992.
20ASHRAE552010,section5.2.3. ElevatedAirSpeed.Thisstandardalsostipulatesthattherequiredairspeedfor
light,primarilysedentaryactivitiesmaynotbehigherthan0.8m/s.Whenunderlocalcontroloftheaffected
occupants,theairspeedmaybeashighas1.2m/swithoccupantcontrol.Thestandardnotesthatthesefigures
areconservativeforactivitiesabove1.3metsandforclothinginsulationlessthan0.5clo.
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comfortatthewarmerendofthecomfortzone,suchasthosefoundintropicalenvironments.
Thisencouragesbuildingdesignerstouseairmovementtoimprovebothenergyandcomfort
performanceandalsoopensopportunitiesforimplementinglowenergysystemsthathave
coolingcapacitylimitations.21ASHRAE55srecentmodificationincreasestheupperlimitofair
movementto1.2m/s,thoughthenumberisnotclearfornaturallyventilatedspaces.Notethat
theupperlimitofrelativehumidityfornaturallyconditionedspacesisalsonotclearlydefined
forthesespaces.
CRITERIA.Giventhecontextofaclassroominthisstudy,airflowcharacteristicsaredesirable
whentheairflowplan(attheseatedheadheightof1.1m)hasahighvelocitywithalowspatial
variation,orvPLANandcsvrespectivelyinthewindtunneltestresults.Moreuniformityin
airspeedacrosstheairflowplanisconsideredtobedesirable,asahighvariationinindoor
airspeedcanleadtopointsthataresimultaneouslytoowindy(i.e.neartheinlet)andpoints
thataretoowarm(i.e.farfromwindows)inthesamezone.Thisstudyassumesthatthe
maximumallowableindoorairspeedis3m/s22andthatoccupantshavethecanreduceair
velocitybyoperatingwindowsorchangingseatsifspeedsarehigherthanpreferred.Thermal
acceptabilityforourpurposesiswhentheSET*adjustedPMV23isbetweenslightlycool(1)and
slightlywarm(1),whichequalsa26%peopledissatisfied(PPD). ASHRAEconsidersaPMV
between 0.5and0.5oraPPDof10%tobeacceptable.Airvelocitiesareconsideredtohave
21Zelenay,K.,Perepelitza,M,Lehrer,D.2010.
22Basedonadiscussionwiththermalcomfortresearchers, 3m/swasconsideredtobeanexuberantnumber;this
numberwasalsothemaximumairvelocityinputallowablefortheASHRAEThermalComfortTool.23TheStandardEffectiveTemperature(SET)modelusesathermophysiologicalsimulationofthehumanbody
Thismodelenablesairvelocityeffectsonthermalcomforttoberelatedacrossawiderangeofairtemperature,
radianttemperature,andhumidity.ASHRAE552010,section5.2.3.2.
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occupantcoolingpotentialwhentheycanoffsethighertemperaturesintheSET*adjustedPMV
thermalcomfortmodel.
2.3 OBJECTIVES
Itisthehopethatthisdocumentshedslightononeofthemanymethodsofstudying
airflowandinspiresarchitects,especiallythosedesigningfortropicalclimates,toconsiderthe
designchallengesassociatedwithnaturalventilationasopportunitiesratherthansimply
acceptingthistobeoutsidetheirscopeandbeyondtheircontrol.
Asdiscussedinsection1.2oftheintroduction,architectshavebeenincreasinglyusing
newtypesofscreensandshadingdevicesthatlikelyaffectairflow.Whileotherformsof
externalshadinghavebeenstudiedintermsofairflowinthepast,screenshadingsystemshave
notbeenanalyzedintermsofairflowbefore.Thepurposeofthisstudyistoassesstheimpact
ofarangeofshadingandwindowconfigurationsonindoorairflowinordertoidentifyhow
specificinletgeometriesaffecttheeffectivenessofwinddrivencoolinginawarmhumid
climate.Whilenaturalventilationcanpassivelycooloccupantsandreduceoreliminatethe
needformechanicalcooling,airflowinbuildingsisinherentlydifficulttoanalyze.Through
examiningofanumberoffaadeinletconfigurations,thisstudyseekstodevelopabasisfor
buildingfaadesdesignprinciplesintermsofnaturalventilation.Itisthehopethatthe
informationpresentedinthisdocumentwillencouragedesignerstoconsiderusingnatural
ventilationintropical
climate
projects
and
help
them
maximize
the
potential
ofnatural
ventilationinbuildingdesign.
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Theimpactofinletfaadecomponents madeupofexteriorshadingdevicesand
windows onnaturalventilationwillbeassessedintermsofthemeanvelocityanddistribution
oftheairflow.Themainquestionsaskedare:
o Whatcombinationsofshadingdevicesandwindowtypescreateuniformlyhighairflow
acrosstheoccupiedzone24?
o Howdoexteriorshadingscreensinfrontofoperablewindowsaffectairflowandshould
theybeusedifnaturalventilationisagoal?
o Iftheshadescreenreducesairvelocity,whatcharacteristicofitsgeometryaffectsthis?
Howdodifferenttypes(e.g.perforatedpanelandthinlouvers)ofshadingdevices
compareintermsofslowingdownorchangingthedirectingofairflow?
o Howdoestheairflowvarywithwindowtype?
o Givenacombinationofshadesandwindowsthateffectivelypromotesairmovement,at
whattimesmightwinddrivenventilationbeacceptableforthermalcomfort?
o Howmightdesignteamsapplythisinaproject?
2.4 APPROACH
Theindependentandinterdependenteffectsofthetwocomponenttypes(shadesand
windows)onairflowareexaminedusingaphysicalscalemodelofaclassroominaboundary
layerwindtunnel.Thedesirableairflowcharacteristicswillhaveahighaveragevelocityratio
withlowvariationacrosstheairflowplan.Thisstudylooksattwotypesofexternalscreen
shades:aperforatedpanelsystemandthinexteriorlouvers;andthreetypesofoperable
windows:awning,casementanddoublehungwindows.Someexamplesofscreenshadesand
windowtypesareshowninFigure21andFigure22.Outofthetestedconfigurations,themost
24ASHRAE552010,7.2.2:HeightAboveFloorMeasurements.Airtemperatureandairspeedshallbemeasuredat
the0.1,0.6,and1.1m(4,24,and43in.)levelsforsedentaryoccupantsatthelocationsspecifiedinSection7.2.1.
Standingactivitymeasurementsshallbemadeatthe0.1,1.1,and1.7m(4,43,and67in.)levels.Theseheights
correspondtoseatedandstandingankle,waistandheadlevels.
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promisin
thermal
gshading
comfortpot
indowcom
entialisass
inationiss
ssedforth
22
electedfor
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Figure22:
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,casement,du
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wning,project
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od
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CHAPTER3 PREVIOUSRESEARCH
Applyingthethermalcomfortstandardsmentionedaboveisnotasimpletaskand
architectsaretypicallynotinvolvedintheanalysisrelatedtocomfortstandards.Typically,
consultingengineersaretheoneswhoemploythesestandards.Simplifiedguidelinesfor
architectshaveattemptedtobridgethisgapandhavehistoricallydiscussedvariousformsof
mechanicalequipmentrequiredforheating,coolingandventilating.Intheseguidelines,
ventilationthroughwindowswastreatedmoreasanalternative,nonessentialstrategy.
3.1 EXISTINGDESIGNGUIDELINES
Researchonnaturalventilationhasbeenconductedatboththeacademicand
professionallevels,usingbothphysicalandmathematicalmodels.Whiletherehasbeensome
efforttoconsolidatesuchresearchintodesignguides,muchthisdatesbacktothe1980sor
earlierandisnoteasilyaccessibleformostpracticingprofessionalengineersandarchitects
today.
Existing
design
guides
common
in
architectural
practices
do
not
have
specific
informationonhowtodesignwindowsandshadesforairflow.Whileitisanexcellent
schematicdesignguideforarchitects,G.Z.BrownsSunWind&Light(SWL)iscursoryinits
mentionoftheeffectsofsunshadesandwindowtypesonairflow;Brownstatesthatshades
canobstructflow.Thisisunderstandable,sincethismightbeofmoresignificanceduringlater
stagesindesign.Thatsaid,BrowndoescitetheRectorateoftheAcademyoftheAntillesand
Guiana(alsoknownastheEducationAuthorityofMartinique),whichhasfinsfordirecting
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airflowthatalsohelpwithshadingtheopenings.25ThereferencesandstudiescitedinSWL
arealsohelpfulforfurtherresearch.
Similarly,MechanicalandElectricalEquipmentforBuildings26
providesusefulrulesof
thumbforchoosingwindowtypesforairflowbasedonpercentageofeffectiveopeningarea,
whichisnotclearlydefined.Figure23(left)wascitedinEnvironmentalControlSystemsby
FullerMoore,referencingEnergyEfficientFloridaHomeBuildingbyVieiraandSheinkopf).
Similarwindows(butwithdifferenteffectiveopeningpercentages)arealsoofferedbyKnaack
inFaades:PrinciplesofConstruction(Figure3,right).Theauthorsabovedidnotdescribehow
thesepercentageswerederived.(ThoughtherewerenaturalventilationstudiesattheFSECat
thetime,theauthorsdonotreferenceothersourcesforthis.)Whilethismaysufficeforvery
earlydesigncalculations,suchomissionsgivenoclueastowhenthesenumbersarereliablefor
laterdesignphases,whenmoredecisions,likethetypeandnumberofopenings,mustbe
made.
Figure23:(Left)Effectiveopenarea,alsocalledwindowporosity,ofvarioustypesofwindowsfromEnergyEfficientFlorida
HomeBuilding,1988,p.73.Itisunclearhowthesepercentageswerederived.(Right)Notetheverydifferenteffectiveopen
areasfromFaades:principlesofconstruction,p.75.
25Brown,SunWindandLightp.184.
26Grondzik,WalterT.,AlisonG.Kwok,andBenjaminStein.2009.Mechanicalandelectricalequipmentforbuildings.
Hoboken,N.J.:Wiley.
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3.2 REGIONSPECIFICGUIDELINES
Additionalspecific,andoftenobscure,designguidelinesfornaturalventilationare
availablefromconferenceproceedingsandenergyresearchcenters,suchastheFloridaSolar
EnergyCenter(FSEC).ExamplesofthisincludeCoolingwithVentilation27forthesoutheastern
UnitedStates,VentilationofWideSpanSchoolsintheHotHumidTropics28,NaturalVentilation
inNorthwestBuildings29.Exceptforthelastbookmentioned,muchofthisworkwasdonein
thelate1970sandearly1980s;whiletheseeffortshavemuchusefulinformation,itisunlikely
thatarchitectswhodonothaveaccesstomajorlibrariescaneasilyfindthem.
3.3 METHODSOFTESTINGWINDDRIVENVENTILATIONINBUILDINGDESIGN
Thoughwinddrivenventilationinbuildingshasbeenusedforalongtime,methodsof
estimatingitsperformancehavenotbeenaroundaslong.Rulesofthumbforarchitectsinvolve
manipulatinginletandoutletareasasafunctionofthefloorarea.Rulesofthumbareperhaps
acceptableforanapproximatednotionduringveryearlydesignphases,butdonotaddressthe
interactionbetweensunshadingandopeningareas.Formoresophisticatednaturalventilation
testing,architectsusuallyrefertoconsultantengineersfordesignguidance.Inturnthese
mechanicaland/orcivilengineersuseavarietyoftoolsforestimatingairflow.Theseinclude:
1) Thedischargecoefficientmethod
2) bulkairflowmodelsbasedonpressurecoefficients
3) computationalfluiddynamics(CFD)
27Chandraetal,1986.TheFSEChaspublishedmanydesignguidesandpapers.
http://www.fsec.ucf.edu/en/index.php28Chand,Ishwar,1977.UNESCOsponsoredresearchdoneatCentralBuildingResesarchInstitute,Roorkee,India.
29Brown,G,andUniversityofOregon,2004.
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Researchersemployanevenbroaderrangeofassessmentmethods.Forthepurposesof
research,methodsoftestingindoorwinddrivenairflowinbuildingsinclude30:
a)
fullandmodelscaleoutdoorinvestigations
b) bulkairflowmodeling
c) computationalfluiddynamics(CFD)
d) theuseofwinddischargecoefficientmethod
e) directmeasurementofindoorvelocitiesinascalemodelwithinaboundarylayer
windtunnel
Thedifferencebetweenthetoolpaletteofthedesignengineerandthatofthe
researcherariselargelyfromthecostsinvolvedwithwindtunneltestingandtheabsenceofa
constructedbuilding(asrequiredinfullscaleinvestigations)totestduringthedesignphase.
Bulkairflowmodelingisnotsoeffectivewhenbuildinggeometriesarecomplexorinthecaseof
simplegeometrieswithlargeopenings(asisoftenthecaseinhot,humidclimates).Ofthenon
physicaltoolsinthepalette,onlyCFDcanprovidesomeguidancetotherelativeperformance
ofdifferentwindowsandshades.ItshouldbenotedthatthekindofCFDusedforbuilding
designsimulations(asopposedtothoseforaircraftdesignsimulation),rarelymodelseddiesor
fluctuationsinvelocitythatarecommoninnaturalwind,becausedoingsowouldbetoo
expensive31.InadditiontothechallengesofmodelingnaturalwindinCFD,utilizingCFD
effectivelyhasasteeplearningcurveandrequiresmuchoperationalexperiencebeforereliable
resultscanbeobtained.Whileeachoftheevaluativemethodshaspositivefeaturesand
drawbacks,windtunnelmodeltestingwasselectedforthepurposesofthisstudy.
30Ernest1991
31Theexcessivecostsincludethatfortechnicallyskilledlabor,manyhoursofworkandhighendsoftware.Based
onaconversationwithDavidBanksofCPPWindEngineeringandAirQualityConsultants
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Therewereanumberofreasonsforthis:windtunneltestinghasallowsforboth
velocitymeasurementsandflowvisualization;exploringthemethodwasrelativelyaccessible;
oncebuilt,physicalmodelsarerelativelyeasytoadjust;mostsignificantly,theBuildingScience
LabatUCBerkeleyhasafunctionalboundarylayerwindtunnelaswellasresearcherswith
directexperiencewiththisspecificwindtunnel.
Ascanbesaidofeverymethod,windtunneltestinghasitslimitations.Inordertofitthe
testingprogramintothewindtunnelmethods,modelscannotobstructmorethan10%ofthe
crosssectionbeforeresultsbecomeunreliable.(Someresearcherskeeptheirmodelsunder
5%.)Thislimitsthesizeofthetestmodel,causingmidandhighrisebuildingschallengingto
study.Thoughoriginallytheideawastotestaroomaspartofabuildingmass,ithadtobe
modeledasaoneroomboxinordertocapturetheadequatedetailrequiredintheshadesand
windows.Inadditiontothis,thewindtunnelhadnotbeenusedtocollectvelocity
measurementsinaboutadecade,somoretimewasrequiredtogettheequipmentfully
functional.
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Figure24.Previousnaturalventilationresearchconductedinthewindtunnel.
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3.4 ACADEMICRESEARCHANDPARAMETRICWINDTUNNELVENTILATIONSTUDIES
Forthisstudy,asurveyofpreviousresearchwasconductedinanefforttoidentifythe
significantparametersaffectingindoorairflow.Bowen(1981)consolidatedthegeneralfindings
ofvariouswindtunnelstudiespriorto1981intoaconferencepaper32.Windtunnelstudieson
naturalventilationinbuildingswerebeguninthe1950s,atTexasEngineeringExperiment
Station(Smith,1951andHolleman1951)andcontinuedintotheearly1990s.Variousbuilding
parametersaffectingindoorairmotionwereinvestigatedwithinthisbodyofwork.
BOUNDARYLAYER/SITEDENSITY.Boundarylayerdescribeslayersofwindneartheground
whicharealwaysturbulentduetoroughnessinthesurfaceoftheearth.Thewindspeediszero
atgroundlevel;theamountitincreaseswithheightdependsonthetypeofterrainandiscalled
aboundarylayerprofile.Thepresenceofneighboringbuildingsreduceswindspeeds.Inthe
windtunnel,theboundarylayerroughnessisgeneratedbyusingwoodblocks.Ernesttested
theeffectsofthreeboundarylayers(terrainscorrespondingtoflatfarmland,villagesand
suburbs)onalowrisebuildingmodelandfoundvirtuallynodifferencesinpressurecoefficients
33.Healsonotedapreviousstudy(AkinsandCermak1976),whereintheaffectofdifferent
boundaryconditionshadmuchmoreofaneffectonhighrisebuildings.
32Bowen1981.
33Ernest1991.p.4041
Figure25.Sobin'sdiagram
describingvariousincidentwind
angleshetested.
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WINDDIRECTION.Givoni(1962)foundthataverageindoorairvelocitywashigherforthe
incidentwindanglesof45thanfor0(Figure25).Sobintestedmultiplewindowproportions
andfoundthisonlytobetrueforhorizontalwindows,whilesquarewindowsperformedbetter
at0.Inhis1977studies,Chandconcludedthatwinddirectioncannotbestudied
independentlyofothervariables.
BUILDINGMASSING.Inhisreportontheventilationoftropicalschoolbuildings,Chand(1977)
comparedvariousbuildingfloorplanshapes;hefoundwindshadowscouldbeminimizedwith
Lshaped(orreentrantcornered)plans.Inasimilarmanner,Aynsley(1979)studiedsixtypesof
freestandinghousesforhothumidclimatesinthecontextofQueenland,Australia.He
concludedthatbothelevatedandgroundlevelhouseswithextendedverandasandendwalls
(types4and2respectivelyinFigure27)couldprovidethehighestcoolingpotentialinthetest
set.Thesearchitecturalfeatures,notsurprisingly,arealsocommontoAustraliashothumid
tropics.ThroughCFDtests,Tantasavasdietal(2001)cametoasimilarconclusion.Hefound
houseselevatedonstilts,ratherthanongroundlevel,tobemoreeffectivefornatural
ventilationintheBangkoksuburbanclimate.
Figure26.Chand
(1976)studied
concludedthatwind
shadowscouldbe
remediedwithre
entrantcorners.
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Figure27:(Left)HousetypestestedbyAynsley(1979).Types2and4(witheavesandendwalls,withandwithoutstilts)
showedthemostcoolingpotential.(Right)DesignstrategybasedonfindingsfromCFDsimulations(Tantasavasdietal,2001)
Atamorebasiclevelofmassing,Ernest(1991)testedtheadditionofmassontohis
baselinebuilding.Headdedonsupplementaryblocksaboveandbesidethebaselinemodel,
althoughnotsimultaneouslyinbothplaces,aswouldbethecaseinamidrisebuilding.When
addingablocktoincreasetheheightofthebuilding,hefounda5%increaseinaverageinterior
airvelocityatsomeangles(between30and75).Therewaslittledifferenceat0,15and30
anglesofincidence.Whenablockwasaddedtoonesideofthebuilding,hefoundlessthana
5%increaseatsomeangles.(Theinteriorairvelocitywasveryclosetothesingleblockexcept
between3075,wheretherewaslessthana5%increase.)Whentwoblockswereaddedtothe
rightandleftsideofthebaseline,theaverageairvelocitiesdecreasedslightly,ascompared
withthesingleblock.
Figure28(left).Addedheightincreasedaveragevelocityslightlyinbaselinebuildingatincidentanglesbetween3075.
Figure29(right).Addedwidthinplandecreasedairvelocityexceptwhenatobliqueanglesbetween3070
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ROOMDEPTHandPROPORTIONS.BothSobin(1983)andChand(1966and1977)testedthe
affectsofroomdepthproportionsonindoorairflow.Inhisstudyonventilationintropical
schools,Chand(1977)concludedincreaseinthespandepthofabuildingreducesthe
achievablewindspeedsatallpointsinsidethebuildingandthatthisreductionwasmore
pronouncedbelowsilllevel,suchasforstudentsseatedonthefloor.Sobins(1983)data
similarlysuggestedthattheairflowinshallowanddeeproomsislargelydependentonwindow
geometry.Inaroomwithvertical,floortoceilinginletandoutletopenings,theairvelocities
significantlydecreasedinthedeeperroomfurtherawayfromthewindow.Forthehorizontal
windowsinSobinsstudies,however,roomdepthdidnotgreatlyaffecttheaverageindoorair
velocitiesinplanorsection;inplantheaverageairvelocityactuallyincreased4%whileit
decreased5%insectionbetweentheshalloweranddeeperrooms.
OPENINGSIZE,SHAPEandLOCATION.Sobin(1983)didanextensivestudyofvariousopening
shapes,sizesandgeometries.Heconcludedthatwindowopeningshapewasthesinglemost
importantwindowdesignparameterindeterminingtheefficacyofwinddrivenventilative
cooling.34Hisfindingssuggestthathorizontalwindowsproducemoreroomairflowatawider
rangeofanglesthansquareorverticalwindows(Figure30).Chand(1968)foundthattheheight
34Sobin,1981.
Figure30.Theimpactofwindow
shapeonairvelocity.(Sobin1981,
modifiedbyChandra1986.)
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33
ofthewindowsillhadasignificanteffectintheairmovementinthelivingzonebetween0.6
and1.2m;asillheightof0.9mor85%ofthedesk(workingplane)heightwasidealforachieving
maximumairmotioninthebreathingzone.
WINDOWGEOMETRYandDETAILS.Manypastwindtunnelventilationstudiesweredoneon
thinwalled,oneroommodelswithasingleinletandasingleoutlet,abasicgeometrythat
mightbefoundinschoolroomsandresidentialstructures.Withfewexceptions,onlyrough
Figure32.Drawingsof
fullscaleandmodel
studiesofdifferent
windowoperationtypes.
Chandra1986,
preprintedfrom
Holleman1951.
Figure31.Smith,1951.
Thebuildingmodel
showedonlyasmall
differenceindetail
comparedtothetest
facility,causingtheflow
patterntobevery
differentfromthatinthe
actualbuilding.The
discrepancyresulted
fromadifferenceinsash
andframedetail.
Figure33.CFDtestofan
extrusiondetailatthe
bottomofanawning
windowforflow
redirectionintothe
occupiedzone.
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opening
sillwere
detailsh
studies(
theSFF
Figure34.
Wall.Belo
EXTERIO
concern
cooling.
includin
studiedt
thatse
weremo
35Carter,Bri
Universityo36
Sobin,1
weremod
notmodele
avepotenti
Figure31an
deralbuildi
eft:semiboxt
.EffectofLouv
PROJECTI
dwithwin
36BothSobi
variousfor
heimpacts
iboxtype
steffective
ian.2008.GSA/
f Buffalo,The
981p.195
ledthati
dwithreali
ltoenhanc
dFigure32
ngbelow).35
peprojectiont
ers(orhorizont
NSandSH
owsystem
nandChan
msofshadi
ofhorizonta
projections
promoting
orphosis/Arup
tateUniversity
,withouta
ticthicknes
eorobstru
aswellasi
stedbyChand
alshade).Chan
DINGDEVI
selectiono
(1971,19
gdeviceso
landproje
(Figure34
r
irmotioni
:
San
Francisco
ofNewYork.(i
34
windowaf
ses.Asasig
tairflowto
naCFDtes
.Middle&right
d,1976.
ES. Inhise
thebasiso
5,and197
fdifferent
tionsonin
ight),made
theoccupi
Federal
building
sert
image
into
ameormo
nificantpar
theoccupie
eddesigno
:EffectofVerti
xtensivest
fthepote
)testedmu
eometries.
oorairmo
upof
an
ov
edzonefor
.Buffalo,NY:S
document)
eablesash.
ofthegeo
dzone,ass
fthewindo
calProjections
dies,Sobin
tialforpas
ltiplefenes
Chandand
ement.The
erhangand
allangleso
hoolofArchite
Oftenwalls
etry,thes
howninear
framedet
ntheWindwa
(1983)was
iveventilati
rationfeat
rishak(197
studyfoun
avertical
fi
incidence
tureandPlanni
and
ly
ailat
rd
ve
res,
1)
,
ng,
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35
between0and90.Chandra(1983)studiedtheeffectsofwingwallsonenhancingnatural
ventilation.
Testsontheeffectofshadingdevicesonindoorairflowhavebeenaddressedthrough
meansotherthanwindtunneltests. Intheexamplesfound,themethodsinvolvedmeasuring
thepressuredifferenceacrossfullscalelouversinapressurizedtestschamberandcomparing
resultswithmathematicalmodels.Tsangrassoulisetal(1997)testedmoveableverticaland
horizontallouversonanoutdoortestcellwithsinglesidedventilationforthepurposeof
improvinganetworkflowbasedmethodoftestingairflowthroughshading.Pittsand
Georgiadis(1994)testedVenetianblindanglesandwindowopeningdegreesinawindtunnel.
Nomentionwasmadeoftheparticulartypeofwindowsusedinthetest.Theyobservedthat
thinlouversatthepartiallyclosedangleof45showedlittleflowreductionandcouldenhance
airflowthroughpartiallyopenedwindows.Whensetat85,however,theblindssignificantly
blockedairflow.Thefindingsinthethreestudiesabovearelimitedtotheregionimmediately
behindthelouvers.Thisinformationishelpful,butlimitedinapplicabilityinthecontextof
tropicalclimateswheremuchmoreflowisneededtoachievethermalcomfort.
Alargeconcentrationofwindtunnelbasednaturalventilationstudiesisconcernedwith
howtocoolbyconvectioninhothumidandhotdryclimates(Chand,Givoni1962).Itisfrom
thesetropicalregionsthatmuchofthisresearchoriginates.IshwarChandworkedinIndiaand
Thailand;Richard
Aynsley
resided
inPapua
New
Guinea
and
Queensland;
Baruch
Givoni
spent
a
significantamountoftimeinHaifa,Israel;HarrisSobindidhiswindtunnelstudiesattheCentre
forTropicalArchitectureattheArchitecturalAssociation,inLondonandtaughtandpracticedin
Arizona.
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36
Thegoalofwinddrivenventilationinhot,humidclimatesistoprovideadequateair
movementprimarilyforbodilycooling.Itisparticularlyinthenonresidentialbuildingsinsuch
climatesthatthefindingsforsuchresearchcanpotentiallyhaveanimpact.
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37
CHAPTER4 METHODS
Thischaptercoversthemethodsinvolvedwiththetestingofascalemodelandits
componentsinaboundarylayerwindtunnel.Eachconfigurationinvolvedtakinginteriorair
velocitymeasurementsinsidethemodelatthreeanglesofincidence:0,45,and90.Testing
beganwithconfigurationsofindividualcomponentsfirstandthenmovedontocombinations
ofcomponentslater.Airvelocitiesarespatiallydescribedthroughisovelocitycontourmapsin
planandsection.Flowpatternsarethendescribedinairflowplansandsectionsdrawnfrom
smokestudiesobservedfirsthandandcapturedonvideo.
4.1 BOUNDARYLAYERWINDTUNNEL
Velocitymeasurementsandsmokestudieswerecarriedoutintheboundarylayerwind
tunnel(BLWT)housedinUCBerkeleysBuildingScienceLaboratory.Thewindtunnelisanopen
circuitdesignwithinteriorcrosssectionaldimensionsof1.5mhighby2.1mwideandan
overalllengthof19.5m.Thefirst12.8mofthewindtunnel,fromthebellmouthinlet,isthe
flowprocessingareaandcontainsacombinationofturbulencegeneratingblocksacrossthe
floortosimulatecharacteristicsofflowapproachingthebuildingmodel.Immediatelyfollowing
theboundaryelementsisa3.7mlongtestsectioninwhichscalemodelsaretestedona2m
diameterturntable.Theturntableisusedtostudytheincidentwindanglesof0,45and90
movingcounterclockwiseinplan.
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Figure35.
4.2
T
withina
modeled
purpose
(describ
expecti
ceilinga
toreceiv
opening
fullyope
twowall
thevario
mm)hol
sealinth
themea
asemodelwith
ODELDES
hemodel,a
lowrise
bui
assinglero
ofmeasuri
dearlier)w
tropicalcli
dafloor.T
einterchan
amountsfo
n.Theexte
sweremad
usheights
scorrespo
egapbetw
urements.
roughopening
RIPTION
tthescale
lding.In
ord
om.Them
ngandvisu
hileseemin
ates,assh
etwowall
eablewind
eachofth
iorshades
ofclearac
ftheoccup
dingtothe
enthepro
s,photograph
f1=10
erto
work
delhasrec
lizingairflo
glyabstract,
owninthei
withwind
owstypesa
windows,
ereoffset
rylicandsc
iedzone.Th
pointsofv
eandthe
38
nddrawing.
IPunits(o
ithinthe
m
nfigurable
.Theoccu
asinglero
ntroduction
wopening
ndexterior
hewindow
0model
redatthe
eclearacry
locitymeas
crylichole.
r1:8),repre
ethodsof
t
indowsan
pancytype
mspaceis
.Themode
weredesig
shades.Wh
configurati
scalefrom
easureme
licceilingo
urements.
Unusedhol
sentsasing
eBLWT,
th
dexteriors
andmethod
notfarfro
lconsistsof
nedasroug
ileitispossi
nswereal
heexterior
theightsc
themodel
rubberwa
sweretap
leclassroo
classroom
adingfort
sinducedli
whatone
fourwalls,
hopenings
bletoadjus
aystested
wall.Theot
rrespondin
as3/8(9.
hercreate
dshutduri
was
e
its
an
oas
tthe
as
her
to
a
g
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39
ThistestisReynoldsnumberindependent,asthemodelpartshavesharpedgesandthe
smallestdimensionsexceedthoseallowable.Atthisscale,openingscanbenosmallerthan1/8
(or3mm)actualsizebeforetheReynoldsnumberbecomesproblematic.Theperforationshad
tobeenlargedinordertonothaveholessmallerthan1/8.Theactualperforationsscaledto
modelsizewouldhaveresultedin1/16diameterholes,whichistoosmallfordynamic
similarity. Thesmallestdimensioninthemodelwasfortheholesintheperforatedpanel
shade,whichare5/32indiameter.(SeeFigure37foravisualcomparison.)
4.3 VELOCITYMEASUREMENTS
VelocitymeasurementsweretakenwithaTSIModel1266hotwireanemometer.The
hotwiresensoratthetipoftheanemometerismostaccurateatmeasuringairflownormalto
thewire37,whichinthiscasemeanslocationsinhorizontalplanesparalleltothewindtunnel
floor.
Velocitymeasurementpointsweretakenintwoplanes.Ahorizontal5x5grid38of
points37(or1.1m)abovethemodelfloor,correspondingtoseatedheadheight,was
establishedtocharacterizeairflowacrosstheroomplan,creatinganairflowplan.Avertical
gridofpointswasalsotakenat4,24,and67(0.1,0.6,and1.7mrespectively)alongthe
centerlineofthemodelfrominlettooutletopenings,creatinganairflowsection39.Itis
expectedthatthecomponentswillbetestedat0,45and90relativetotheincidentwind,
with0
being
head
on
from
inlet
to
outlet
and
45
and
90
turned
inthe
counterclockwise
directionfromabove.Withtwentyfivepointsinplanandtwentyinsection(and5thatoverlap
37Cermak,1984[findpage]
38The5x5horizontalgridintheoccupiedzonecorrespondstotheworkofGivoni,SobinandChand.Sobinalso
useda5x5gridofpointsinsection.39Sobinusedthistermtodescribethesemeasurementplanes.
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40
both),fortydifferentpointsweremeasuredinsidethemodelforeachsetupateachangleof
incidence.
AirflowintheBLWT,likenaturalwind,exhibitsmuchfluctuationinvelocity.Innatural
wind,especiallyinurbanconditions,thereisyetahigherdegreeoffluctuation,aslargereddies
arepossible.Tominimizetheeffectsoffluctuationduringthevelocitymeasurements,each
pointwasmeasured900timesoveroneminute.Themeanwindvelocityduringthatminute
wascalculatedbyacustomizeddataacquisitionprograminLabView8.Themeanvelocityat
eachpoint(vi)isthendividedbythereferencevelocity(vref),takenfromanunobstructed
locationtheapproachflow,inordertoobtainvelocityratios.Inthiscase,thereferencevelocity
wastakenfromapointmorethanthreetimesthemodelheightandatthesameelevationas
theplanmeasurementsintheunobstructedstreambetweenthemodelandturbulenceblocks.
Velocityratiosaredimensionlessvaluesthatalonehavenotmeaning;itisonlywhentheyare
usedwithwindanddatathattheybegintosuggestinactualairvelocitiesandthussignificance
foraspecificcase.
Therearemanyfactorsthataredifficulttocontrolinthewindtunnel.ItisImportantto
identifywhatismorecontrolledandwhatislesscontrolled.Inthiscase,havingaboundary
profilewasdeemedmoreimportantthanhavinganappropriatelyscaledboundarylayer
profile,sincelittledifferenceexistedbetweenvelocityandpressuremeasurementsatdifferent
boundarylayer
scales
for
previous
low
rise
building
studies
40
.
40Ernest,1991.p.4041
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4.4 F
F
attached
photogr
ThoughI
footage
physicall
observat
smokeh
quickly;
againon
Figure36.I
conditions
visualizatio
4.5 S
Ofthe
e
screena
41Thispar
forhuman
LOWVISUA
lowvisualiz
toacompr
phswasca
magesalon
ashelpful
changevi
ionswithin
dtobeint
hisrequire
cethemod
agestakenfr
t45.Thewoo
nofthinlouver
ELECTIONo
teriorshadi
efrequentl
icularbounda
breathing. Ti
LIZATION
tionwaso
essedairho
turedfrom
arenotve
inreviewin
wingangle
intheoccup
oducedfor
fillingthe
lwasfilled.
mflowvisualiz
dblocksusedt
sandroughop
fSHADING
ngstrategie
yvisibleinc
rylayerwindt
aniumtetrac
servedwit
seandlater
thesestudi
rydescripti
whatwas
attimes.)
iedzone.F
instantane
odelwith
ationusingultr
atcontributet
ningat0.
EVICES&
sdiscussed
ontempora
unnelwithin
loride,them
41
smokec
atheatrical
esinorder
easthefo
mpirically
ogisdense
robserving
usobservat
mokewith
sonicfog.(Lef
otheboundary
INDOWT
inChapter
yhighperf
sharedoffice
recommont
eatedwith
smokema
oobservei
doesnotp
bservedin
rthanairan
flowinthe
ions.Often,
thefanoff
)Modelwitha
layerarevisibl
PES
,the
perfo
rmancebui
space,sothe
peused,isto
anultrasoni
hine.Video
teriorflow
otograph
pace.(Itw
dthiswass
upperporti
thefogwo
ndswitchin
ningwindowi
einthebackgr
atedscreen
ldings.Ast
typeofsmoke
ictobreathe.
cfogger41
footagean
direction.
ell,video
simportan
atisfactory
onsofther
lddissipat
gitbackon
nnearstillair
und.(Right)Fl
and
louver
erecanbe
usedhadtob
to
or
om,
w
a
esafe
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widevariationinshadingdevices,thoseselectedfortestingweredesignedandconstructedto
haveaporosityof53%.WhiletheperforatedpanelwasmodeledaftertheSanFrancisco
FederalBuilding(SFFB),thelouverscreenwasnotmodeledafteraparticularbuildingexample,
thougharevisuallyrelatedtotheTerryThomasbuildingandNew42ndStreetStudios.
Combinationsofshadingdevicesandwindowtypeswerealsoselectedonthebasisoftheiruse
inhighprofilegreenarchitecture,suchasthosepreviouslynoted.Theperforatedpanelsystem
basedontheSFFB,wasmadewithperforationsscaledupforwindtunnelmodeling,as
mentionedinsection4.2.Thethinlouveredscreenismadeupof4xlouverstilted22.5
downwardandspaced3and7oncenter(forviewandtoequalizeporositywiththe
perforatedpanel).Thedimensionsofthelouversarecomparabletothatofcommercially
availableexteriorVenetianblinds.
Figure37.Perforatedpanelscreen.Left:viewofperforatedscreenasconstructed.Middle:detailviewofactualscreentested
withlargerholes,butequalporosity.Right:screenasdrawninelevation(Murray2009).
Figure38.Thinlouverscreen.Left:Generalviewofthinlouverscreenasconstructed.Right:detailviewofactuallouver
screentested.
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43
Figure39.Left:theSanFranciscoFederalBuildinghasawningwindowsbehindsaperforatedpanelscreen.(Murray2009).
Figure40.Right:TheNew42ndStreetStudios,NewYork.PlattByardDovelWhite,2000.Elevationandsection.(Murray
2009)
Figure41.(Left)TerryThomasBuildinghasawningwindowsbehindsexteriorvenetianblinds.Imagefrom
.Figure42.(Right)Windowopeningtypestested.(Chandra1986)
*
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THISPAGEISINTENTIONALLYLEFTBLANK
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Atrendcommontoallthetestswasthattheflowstreamwouldexpandanddecelerate
asitmovedpastthewindowframe,mostclearat0.Eddieswouldformaroundtheopenings
insidethewindows.Thelowestvelocityratiostendedtooccurbelowtheinletwindow.Not
surprisinglyata90incidentwind(paralleltothewindow),vPLANandvSECTwerethelowestas
comparedtotheotheranglestested.
Withtheexceptionoftheawningwindow,themaximumvPLANandvSECTtendedtooccur
atthe45obliqueincidentwindangleallfaadeconfigurationstested,astheroughopening
shapeishorizontal42.(Fortheawningwindow,thoughthemaximumvPLANandvSECToccurredat
0incidentwindangle.)At45and90,theangledincidentwinddirectionresultedina
clockwiserotationintheindoorairstream.
Generally,vSECTtendedtobegreaterthanvPLANat0and45.Theexceptiontothiswas
thedoublehungwindowtest,whichhadconsistentlyhighervaluesforvPLANatallangles.The
dimensionofthisinletopeninginsectionwasalsoabouthalfoftheotherinletwindowstested.
Thetest
results
were
influenced
by
the
ratio
between
inlet
and
outlet
size
(which
vary
fromabout2:1or1:1).Itisdifficulttoseparatetheeffectsofinletwindowgeometry
obstructionsfromtheinfluencesofthisparticularexperimentalsetup(whentheoutletareais
lessthanorequaltotheinletarea)43.Itiscommoninlargeandespeciallywideopeningsto
havesimultaneousinflowandoutflowatthesameopening44,acharacteristicofsinglesided
ventilation.
42ThisisconsistentwithSobinsfindingsassociatedwithhorizontalwindows.
43BasedonaconversationwithDavidBanksofCPPWind.
44Sobin(1981)alsonoticedthisphenomenoninhisstudyofhorizontalwindows.
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Table1.Resultsfromtestsperformed.VPLAN=meanvelocityratioforoccupiedareasinplan;VSECT=meanvelocityratiofor
occupiedareasinsection.Yellowhighlightindicatesthehigherallpointsmeanvelocity,eitherinplanorsection,foratestat
agivenangleofincidence.Orangehighlightandboldtextindicatethehighestairallpointsmeanvelocitywithina
configurationatthethreeanglestested.SPLANandSSECTarethestandarddeviationofthevelocityratiosinplanandsection
respectively.Csv=coefficientofspatialvariation.
Shade InletWindow OutletWindow Test AngleV
PLAN
S
PLAN Csv
V
SECT
S
SECT Csv
none none none RO+RO 0 57.5 24.1 0.4 73.9 39.6 0.5
none none none RO+RO 45 69.8 33.1 0.5 79.3 39.2 0.5
none
none
none RO+RO 90 20.9 13.5 0.6 19.2 5.4 0.3
none none DoubleHung,LO RO+VSLO 0 25.1 13.0 0.5 34.2 16.9 0.5
none none DoubleHung,LO RO+VSLO 45 33.0 22.5 0.7 34.2 26.0 0.8
none none DoubleHung,LO RO+VSLO 90 17.7 13.4 0.8 13.1 5.2 0.4
none none DoubleHung,UO RO+VSUO 0 21.9 12.1 0.6 32.5 20.1 0.6
none none DoubleHung,UO RO+VSUO 45 40.9 22.0 0.5 46.0 26.7 0.6
none none DoubleHung,UO RO+VSUO 90 14.3 11.9 0.8 10.4 7.0 0.7
none Awning DoubleHung,UO AW+VSUO 0 50.9 25.8 0.5 77.3 44.1 0.6
none Awning DoubleHung,UO AW+VSUO 45 44.8 20.1 0.4 47.8 24.9 0.5
none Awning DoubleHung,UO AW+VSUO 90 10.7 8.2 0.8 9.0 5.2 0.6
none Casement DoubleHung,UO CA+VSUO 0 22.6 11.6 0.5 32.4 17.8 0.5
none Casement DoubleHung,UO CA+VSUO 45 27.8 17.8 0.6 42.2 20.9 0.5
none Casement DoubleHung,UO CA+VSUO 90 18.0 16.5 0.9 17.2 5.8 0.3
none DoubleHung,LO DoubleHung,UO VSLO+VSUO 0 46.7 32.5 0.7 44.6 23.3 0.5
none DoubleHung,LO DoubleHung,UO VSLO+VSUO 45 58.9 29.9 0.5 53.9 27.8 0.5
none DoubleHung,LO DoubleHung,UO VSLO+VSUO 90 11.9 21.2 1.8 7.2 5.1 0.7
LouverScreen none DoubleHung,UO LSRO+VSUO 0 12.3 3.8 0.3 25.6 14.3 0.6
LouverScreen none DoubleHung,UO LSRO+VSUO 45 41.2 15.9 0.4 49.8 27.4 0.6
LouverScreen
none
DoubleHung,
UO
LS
RO
+VS
UO
90 18.7 14.6 0.8 13.9 12.4 0.9
PerfPanel none DoubleHung,UO PFRO+VSUO 0 10.6 2.8 0.3 21.7 13.4 0.6
PerfPanel none DoubleHung,UO PFRO+VSUO 45 34.3 11.7 0.3 46.4 25.5 0.6
PerfPanel none DoubleHung,UO PFRO+VSUO 90 19.3 15.9 0.8 14.7 11.2 0.8
LouverScreen Awning DoubleHung,UO LSAW+VSUO 0 17.7 7.5 0.4 30.6 19.3 0.6
LouverScreen Awning DoubleHung,UO LSAW+VSUO 45 43.5 19.2 0.4 46.6 24.3 0.5
LouverScreen Awning DoubleHung,UO LSAW+VSUO 90 13.7 11.1 0.8 11.3 8.5 0.7
LouverScreen DoubleHung,LO DoubleHung,UO LSDHLO+VSUO 0 30.9 13.6 0.4 39.5 22.0 0.6
LouverScreen DoubleHung,LO DoubleHung,UO LSDHLO+VSUO 45 50.0 25.3 0.5 54.9 27.7 0.5
LouverScreen DoubleHung,LO DoubleHung,UO LSDHLO+VSUO 90 12.6 14.1 1.1 7.6 6.2 0.8
PerfPanel Awning *60%complete
DoubleHung,UO PFAWLO+VSUO 0 12.0 2.4 0.2 25.9 22.2 0.9
PerfPanel Awning DoubleHung,UO PFAWLO+VSUO 45 36.7 14.0 0.4 45.6 24.0 0.5
PerfPanel Awning DoubleHung,UO PFAWLO+VSUO 90 13.7 12.0 0.9 12.0 9.4 0.8
PerfPanel DoubleHung,LO DoubleHung,UO PFVSLO+VSUO 0 32.2 16.6 0.5 33.3 18.4 0.6
PerfPanel DoubleHung,LO DoubleHung,UO PFVSLO+VSUO 45 44.1 22.8 0.5 50.4 25.2 0.5
PerfPanel DoubleHung,LO DoubleHung,UO PFVSLO+VSUO 90 14.0 16.5 1.2 8.5 8.3 1.0
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Ditribuo of iet tet -
widow, hde d combied
- i term of the me eocity
ro i (V) d the
coeciet of rice
(C) for ge of icidece
teted.
Ide codio woud he
high Vplan d ow Csv.
Ditribuo widow tet t
ech of the icidet ge.
Other tet re how greyed
out. Note the three dieret
chge i Vplan t 0o, 45
od
90o.
Ide codio woud he
high Vplan d ow Csv.
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5.1.1 OUTLETOPENINGTESTS
Whatqualitiesaredesirableinanoutletopeningforstudyingfaadeinletconditions?
Thepurposeoftheoutletopeningtestistocharacterizetheoutletopeningintermsofindoor
flowinordertodeterminewhichoutletwindowtousewithallfollowingfaadeinlettests.The
outletopeningareaaffectshowairflowsthroughtheinletwindow;thisinturnimpactst