EScholarship UC Item 5087z1zd

8/11/2019 EScholarship UC Item 5087z1zd

1/104

eScholarship provides open access, scholarly publishing

services to the University of California and delivers a dynamic

research platform to scholars worldwide.

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.

Copyright Information:All rights reserved unless otherwise indicated. Contact the author or original publisher for anynecessary permissions. eScholarship is not the copyright owner for deposited works. Learn moreat http://www.escholarship.org/help_copyright.html#reuse
https://escholarship.org/https://escholarship.org/uc/item/5087z1zdhttps://escholarship.org/uc/cedr_cbe_eshttps://escholarship.org/uc/search?creator=Hildebrand%2C%20Penapa%20Wankaeohttp://www.escholarship.org/help_copyright.html#reusehttps://escholarship.org/uc/item/5087z1zdhttps://escholarship.org/uc/cedr_cbe_eshttps://escholarship.org/uc/search?creator=Hildebrand%2C%20Penapa%20Wankaeohttps://escholarship.org/uc/ucbhttps://escholarship.org/uc/cedr_cbe_eshttps://escholarship.org/uc/cedr_cbe_eshttps://escholarship.org/https://escholarship.org/https://escholarship.org/https://escholarship.org/


2/104

ShadingandCooling:ImpactsofSolarControlandWindowsonIndoorAirflow

by

PenapaWankaeoHildebrand

Athesissubmittedinpartialsatisfactionofthe

requirementsforthedegreeof

MasterofArchitecture

inthe

GraduateDivision

ofthe

University

of

California,

Berkeley

Committeeincharge:

ProfessorM.SusanUbbelohde,Chair

ProfessorCharlesC.Benton

ProfessorPeterC.Bosselmann

Spring2011

MS Thesis, Dept. of Architecture, UC Berkeley 2011 http://escholarship.org/uc/item/5087z1zd


3/104

i

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



4/104

ii

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..................................................................................................



5/104

iii

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.



6/104

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.



7/104

2

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.



8/104

3

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



9/104

4

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.



10/104

T

narrowf

possible

outdoor

addition

shadedt

I

directly

roofsth

vernacul

includes

bringing

cleardif

glassto

hehighroo

loorplates

fornatural

spaceslike

lrooms.G

heexterior

thetropic

boveinthe

tgiveprote

ar,thereis

creeningel

inlightand

erentiation

eparateins

salsoallow

ndtheorga

entilationa

hecourtyar

lleriesand

allsandwi

,thesunhi

skyresults

ctionfromr

otalwaysa

ments,suc

air.Feature

betweensh

ideand

out

edthewar

nizationof

nddayligh

d,orterrac

erandahsp

ndows,con

stheEarth

inhightem

ainalsosha

cleardistin

asinwoo

likelattice

adeandwi

ide.

5

airtorise

nitscluste

ingtobem

,orthegal

rovidedsha

tributingto

atahighan

eratures. I

dethewall

ctionbetwe

orstonela

orkandsh

dowintrop

out,helping

edaround

oreeffectiv

leriesandv

detothese

keepingthe

gle.Astron

nplaceslike

andprotec

enwallsan

tticework,t

utterssugg

icalbuildin

keepthein

courtyard

. Inthesel

randahs,w

outdoorro

indoorsco

,brightsun

Southeast

tfromglare

windows.

blockdire

stthatthe

s.Rarelydi

Fi

la

A

a

o

w

c

P

(S

teriorscool.

lsomadeit

atitudes,

ereusedas

ms,andals

l.

suspended

sia,thesa

.Inthis

indowsof

tsunwhile

ewasalso

buildings

gure2. Left:st

tticeAgraFort,

ra,India.(pho

thor)Right:

oodenlattice

eningabove

ovenbamboo

nstructioninL

abang,Laos.

omsanuk,2004

The

o

e

ten

o

se

ne

oby

all

ang

)



11/104

6

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.



12/104

7

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



13/104

8

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.



14/104

clearvis

building

(Morpho

Cultural

Museum

Educatio

Seattle(

spaces,t

thought

altrendin

.Examples

sis),theTor

entreinN

(Herrzog&

nAuthority

eberTho

heimpacto

hefullexte

ontempora

ofscreensy

reCubeOff

wCaledoni

deMeuron

inMartiniq

pson).Som

fthesescre

toftheiri

ryarchitect

stemsinbui

icetowerin

a(RPBW),t

Arkitekten)

e(Hauvett

eofthese

ntypesha

pactsisun

9

uraldesign,

ldingsinclu

Guadalajar

e NewYor

theNew

&Associ

uildingsare

ingsystem

nown,des

bothintro

etheSan

(EstudioC

kTimesBuil

useuminN

),andtheT

shownbel

sislikelyha

itetheirar

icalandno

ranciscoFe

rmePins),

ding(RPBW

ewYork(SA

erryThoma

w.Innatur

esomeaff

hitecturalp

Figur

Cont

upof

pane

Whil

natu

ane

scree

archi

Figur

scree

inar

right

Fede

(Mor

(Estu

Tijba

(Ren

Wor

tropical

eralBuildi

theTijbao

),theDeYo

NAA),the

buildingin

llyventilat

ctonairflo

rominence.

e7.NewMuse

emporaryArt:c

expandedmet

l.(SANAA)Ne

ethebuildingis

allyventilated,

ampleoftheu

nsinpopular

tecture.

e6:Examples

nshadingsyste

hitecture:(left

)SanFrancisco

ralBuilding

phosis),Torre

dioCarmePino

louCulturalCe

oPianoBuildin

shop).

g

ung

d

w,

mof

lose

al

York.

not

itis

eof

f

ms

to

ube

s),

ter

g



15/104

10

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



16/104

11

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



17/104

12

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.



18/104

centersa

highrise

Thought

makeup

lowrisec

Figure16.

Hoerbst.ht

Figure17.L

KathleenH.

courtesyC

10EdMazareductioni

dtheyaree

uildings.Th

epercentag

bout77%o

lassroomsar

ETIHandmad

tp://www.akd

eft:classroom

)Right.Classro

kieStephens)

riaisthefountheclimatech

speciallytypi

yareeasier

efortropical

thetotalco

ebelow.Exc

School,Dinajp

.org/architect

uildingatChia

minterior,sh

derofArchiteangecausinggr

calatacitys

andcheaper

regionsisun

mercialbuil

ptfortheR

ur,Bangladesh.

re/project.asp

gMaiInternat

wingjalousie

ture2030,a

eenhousegas(

13

edges,asth

torenovate,

known,itisl

dingstockin

yalOaksSch

25.6Nlatitude

id=3392Access

ionalSchool,C

indowsbehind

onprofitorgaHG)emissions

yarelessco

ascompare

ikelytobehi

theU.S.10

Ex

ool,theothe

.AnnaHeringe

ed5January2

iangMai,Thail

insectscreens.

nizationwhosoftheBuilding

stlytobuild

tomid orh

gh,sincelow

amplesofon

rsareintrop

randElkeRos

11)

and.18.8Nlati

(1971CCCClari

egoalitisto

ector

Fi

O

C

la

L

(L

O

1

hanmid an

ighrisebuild

risebuilding

eroomdeep

icalclimates

ag,2005.(Kurt

ude.(Stephens

onCall(yearbo

toachieveadr

gure15.Left:R

aksSchool,Dua

lifornia.34.1

titude.Maynar

ndon,1951.

yndon1993)Ri

aiSection.(Nin

98)

ings.

s

,

.

,

ok,

matic

yal

rte,

d

ht:

dra



19/104

14

Figure18.TransitionalSchool,Jacmel,Haiti.18Nlatitude.JohnRyanandPlanInternational,2010.(JohnRyan)

Figure19.PrimarySchool,Gando,Tenkodogo,BurnikaFaso.11.5NLatitude.DibdoFrancisKr,2001.(FrancisKr

Openarchitecturenetwork.orgAccessed5January2011)



20/104

15

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



21/104

16

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.



22/104

17

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



23/104

18

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.



24/104

19

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.



25/104

20

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.



26/104

21

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.



27/104

promisin

thermal

gshading

comfortpot

indowcom

entialisass

inationiss

ssedforth

22

electedfor

tropicalcli

moredeta

mateofBa

iledexplora

gkok,Thail

Figure22:

Types.(Arc

Standards

left:awnin

action,hop

combinatio

multiplety

including,a

andhoppe

Bottomleft

jalousie,ve

horizontall

single and

Figure21.S

systemsar

contempor

Fromleftt

panels,thin

slats.

tion,where

nd.

indowOperat

itecturalGrap

1thed.p.186)

,casement,du

peranda

nwindow,with

esinonefram

wning,project

windows.

:horizontalslid

rticallypivoted,

pivoted,and

doublehung.

creenshading

prevalentin

ryarchitecture

right:perforat

louversandw

the

ion

ic

op

al

e,

d

ing,

.

ed

od



28/104

23

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



29/104

24

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.



30/104

25

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.



31/104

26

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



32/104

27

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.



33/104

28

Figure24.Previousnaturalventilationresearchconductedinthewindtunnel.



34/104

29

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.



35/104

30

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.



36/104

31

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



37/104

32

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.)



38/104

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.



39/104

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,



40/104

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.



41/104

36

Thegoalofwinddrivenventilationinhot,humidclimatesistoprovideadequateair

movementprimarilyforbodilycooling.Itisparticularlyinthenonresidentialbuildingsinsuch

climatesthatthefindingsforsuchresearchcanpotentiallyhaveanimpact.



42/104

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.



43/104

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



44/104

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.



45/104

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



46/104

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



47/104

42

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.



48/104

43

Figure39.Left:theSanFranciscoFederalBuildinghasawningwindowsbehindsaperforatedpanelscreen.(Murray2009).

Figure40.Right:TheNew42ndStreetStudios,NewYork.PlattByardDovelWhite,2000.Elevationandsection.(Murray

2009)

Figure41.(Left)TerryThomasBuildinghasawningwindowsbehindsexteriorvenetianblinds.Imagefrom

.Figure42.(Right)Windowopeningtypestested.(Chandra1986)

*



49/104

44

THISPAGEISINTENTIONALLYLEFTBLANK



50/104


51/104

46

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.



52/104

47

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,UO RO+VSUO 0 21.9 12.1 0.6 32.5 20.1 0.6



none Awning DoubleHung,UO AW+VSUO 0 50.9 25.8 0.5 77.3 44.1 0.6



none Casement DoubleHung,UO CA+VSUO 0 22.6 11.6 0.5 32.4 17.8 0.5



none DoubleHung,LO DoubleHung,UO VSLO+VSUO 0 46.7 32.5 0.7 44.6 23.3 0.5



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



LouverScreen Awning DoubleHung,UO LSAW+VSUO 0 17.7 7.5 0.4 30.6 19.3 0.6



LouverScreen DoubleHung,LO DoubleHung,UO LSDHLO+VSUO 0 30.9 13.6 0.4 39.5 22.0 0.6



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





53/104

47a

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.



54/104

48

5.1.1 OUTLETOPENINGTESTS

Whatqualitiesaredesirableinanoutletopeningforstudyingfaadeinletconditions?

Thepurposeoftheoutletopeningtestistocharacterizetheoutletopeningintermsofindoor

flowinordertodeterminewhichoutletwindowtousewithallfollowingfaadeinlettests.The

outletopeningareaaffectshowairflowsthroughtheinletwindow;thisinturnimpactst

Documents

EScholarship UC Item 5087z1zd