Whole House Fans: Benefits And Description

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Title:
Whole House Fans: Benefits And Description
Physical Description:
Fact sheet
Creator:
Cook, Gary D.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.

Notes

Acquisition:
Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"EES-32"

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Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the submitter.
System ID:
IR00004799:00001


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Florida Energy Extension Service TheInstituteofFoodandAgriculturalSciencesisanEqualOpportunity/AffirmativeActionEmployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,ornationalorigin. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/JohnT.Woeste,DeanWholeHouseFans:BenefitsandDescription1GaryD.Cook2InFlorida'smildclimatewholehousefansoffer anexcellentopportunitytosaveenergyandmoney whencomparedwiththealternativeofusing mechanicalairconditioning.Toreapthemaximum benefitfromawholehousefan,attentionshouldbe giventopropersizing,installation,andoperationof thefan.BENEFITSThewholehousefanisanenergyefficient substituteforairconditioningduringcertainportions ofthedayandyearwhenoutsideconditionsare favorable.InmostareasofFlorida,thereareabout 120dayswhenthewholehousefanmaybeused effectively.Athreetonairconditionertypicallyused tocoola1500squarefoot(SF)homedrawsabout5 kilowattsofpower.A30inchwholehousefan movingabout5100cubicfeetperminute(CFM)of airdrawslessthan0.5kilowattsofpower.At7.5cts akilowatthour(Kwh)thattranslatestoasavingsof $.34(4.5kilowattsx$.075)foreachhourthatthe wholehousefanissubstitutedfortheairconditioner. Aproperlyselected,installed,andoperatedfancan reduceoverallcoolingcostsbyasmuchas50%. Wholehousefanscostaboutasmuchasagood ceilingfan($150-300).Savingsusuallypayforthefan inlessthanthreeyears. ThewholehousefanenablesFloridaresidentsto achievepositivebenefitsbecauseoffour characteristics: 1)Itproducesa windchilleffect forthe occupants makinghigher temperatures (82-88degrees) feeljustas comfortableas lowertemperatures(74-78degrees)without airmovement. 2)Byflushingthehousewithhighvolumesof outsideair,itkeepstemperaturesfrom buildingupontheinsidefrominternaland radiantloads,thusdelayingtheneedforthe airconditioner. 3)Itreducesthetemperatureoftheatticby about10degreesFonawarmsummerday. Thissignificantlyreducesthemeanradiant temperature(MRT)oftheceiling.Mean radianttemperatureshaveahighimpacton ourcomfortlevel. 4)Awholehousefancanquicklyremove pollutantswithinthehousesuchascigarette smoke,cookingodorsandharmfulhousehold cleanerandsprayemissions. Thesebenefitscanbeoptimizedbyproper selection,installation,andoperation.Forexample, operatingthewholehousefanduringperiodsofvery 1.ThisdocumentwaspublishedasFactSheetEES-32,FloridaEnergyExtensionService.Formoreinformation,contactyourcountyCooperative ExtensionServiceoffice. 2.EnergyExtensionSpecialistforBuildingConstruction,FloridaEnergyExtensionService,InstituteofFoodandAgriculturalSciences,University ofFlorida,Gainesville. TheFloridaEnergyExtensionServicereceivesfundingfromtheGovernor'sEnergyOffice.Theinformationcontainedhereinistheproductof theFloridaEnergyExtensionServiceanddoesnotnecessarilyreflecttheviewsoftheGovernor'sEnergyOffice.

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highhumiditymaybecounterproductiveevenif outsidetemperaturesaremoderate. Therearethreefactorsthataffectcomfort:air movement,temperatureofadjacentsurfaces,and relativehumidity.Generally,alightlyactiveperson willfeelcomfortableinsurroundingswithsurface temperaturesaveraging78degreesFandstillairat 78degreesFand50%relativehumidity.Moderate airmovementwillenableapersontofeelcomfortable withairtemperaturesashighas90degreesFand 50%relativehumidity(seeTable1).However,afan shouldnotbeusedwhentheoutsideairtemperature ismorethan85degreesF.Fanuseduringthis periodwillonlydrawhotairintothehouseincreasing heatbuildupinwalls,floors,andfurniture.Higher surfacetemperatureradiationmightthenoffsetthe windchillfactor.OPERATIONTheoperationofawholehousefanisrelatively simple.Usethefanwhentheoutsideairtemperature andrelativehumidityconditionscanproduceawind chillorperceivedtemperaturethatislowerthanthe insideofthehouse. Generally,thewarmestpartofthedayoccurs around3pmandthecoolestpartofthedayisaround 6am.Unfortunately,themosthumidpartoftheday generallyoccursearlyinthemorningwhen temperaturesarecoolest.Theexceptiontobothis whenfrequentafternoonthunderstormsoccurduring Floridasummers.Temperaturesthendropand relativehumidityrisesto100%.Wholehousefans shouldnotbeoperatedduringperiodsofrainor otherhighhumidityconditions.Atthesetimes,the fanwilldrawinmoistairallowingbooksand materialsmadeofwoodandfabrictoabsorb moisture.Thiscancontributetomoldandmildew problemsandahigherloadontheairconditioner whenused.Ageneralruleisnottousethefanwhen therelativehumidityexceeds85%.Acombination thermometer/humidistatwouldproveawise investmenttoaidinthedecisionofwhentooperate thefan.HUMIDITYAlthoughoutsidetemperaturesinFloridacan exceed100degreesF,itisraretohavetemperatures greaterthan94degreesF.SouthFloridacoastal areasrarelygettemperaturesover90degreesF althoughhumiditylevelsaregenerallyhigher.Mean temperaturesandestimatedmeanrelativehumidity levelsinvariouslocationsinFloridaareprovidedin Table2.Thistableshowsthereisampleopportunity tousethewholehousefanthroughoutFloridaeven inthesummerseason.POLLUTANTSWholehousefanscanbeusedtoremoveindoor pollutantssuchashouseholdcleaningproductfumes, formaldehydeemissions,hydrocarbons,insecticide fumes,smoke,nitrogendioxide,andcarbonmonoxide fromsmokersandgascookingandchlorinefrom bleach.Bymovingahighquantityofoutsideair throughthehouse,awholehousefancancleara smokeyhomeinlessthanfiveminutes.Itwouldtake theaveragesmallaircleanermorethan24hoursto dothesamejob. Prudentuseofthewholehousefanis recommendedduringperiodsofhighoutside pollutionlevels.Localweatherreportsgenerally reportairqualityindices.Nearbyconstructionmay producemorethantheaverageamountofairborne dirt.Underaverageconditions,theuseofthewhole housefanwillnotincreasedustinthehouse.Infact, thereissomeevidencetosuggestitwillcontributeto acleanerhousebecauseairmovementwillnotlet finedustsettle. Ifanairconditioneristobeusedwiththewhole housefan,theiroperationshouldbecoordinatedfor maximumbenefit.Neverusethewholehousefan andtheairconditioneratthesametimeexceptto clearthehouseofpollutantssuchassmokeand odors. Insummary,theproperselection,installation,and operationofwholehousefancanprovidemanyextra

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Page3 Table1. WeatherDataforFloridaLocations WeatherDataforFloridaLocations Location Months Mean Temperature Estimate Mean Relative Humidit y Mean Rainfall Inches Gainesville May 76degF 63% 3.54 June 80degF 69% 6.81 August 81degF 73% 8.25 September 79degF 73% 5.67 Jacksonville May 74degF 70% 3.22 June 79degF 73% 6.27 August 81degF 73% 7.89 September 78degF 79% 7.83 KeyWest May 81degF 68% 2.51 June 84degF 70% 4.55 August 85degF 72% 4.47 September 83degF 72% 7.34 Miami May 78degF 70% 6.12 June 81degF 73% 9.00 August 83degF 75% 6.72 September 82degF 78% 8.74

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Page4 Table2. WeatherDataforFloridaLocations,Continued WeatherDataforFloridaLocations Location Months Mean Temperature Estimate Mean Relative Humidity Mean Rainfall Inches Orlando May 78degF 63% 2.94 June 81degF 69% 7.11 August 83degF 72% 6.73 September 81degF 73% 7.20 Pensacola May 75degF 71% 4.25 June 81degF 69% 6.30 August 82degF 77% 6.67 September 78degF 70% 8.15 Tampa May 77degF 69% 2.41 June 81degF 69% 6.49 August 82degF 74% 8.00 September 80degF 77% 6.35 Source:NationalOceanographicandAtmosphericAdministration

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Page5 hoursofcomfortbydrawinginrelativelymildoutside airandremovinghot,staleairfromahomeby pushingitthroughtheattic,coolingitintheprocess. Coolingcostscanbereducedbyasmuchas50% comparedtousinganairconditioneralone.BIBLIOGRAPHY1.Cook,GaryD.,"AGuideToResidentialEnergy EfficiencyinFlorida,"EES7,EnergyExtension Service,InstituteofFoodandAgricultural Sciences,UniversityofFloridaincooperation withtheGovernor'sEnergyOffice,1981. 2.Cook,GaryD.,"Design,Marketingand OperationofEnergyEfficientBuildings,"Energy ExtensionService,InstituteofFoodand AgriculturalSciences,UniversityofFloridain cooperationwiththeGovernor'sEnergyOffice, 1982(limitededition). 3.Farber,E.A.,Wiggins,D.B.,Podris,F.I., Murdoch,J.A.,"AtticVentilation,"Technical Report,FloridaGovernor'sEnergyOfficein cooperationwithSolarEnergyandEnergy ConversionLaboratory,UniversityofFlorida. 4.Lafavore,Michael,"Something'sintheAir,"New ShelterMagazine,RodalePress,Emmaus, Pennsylvania,May/June1982. 5.NewShelter'sTestingDepartment,"ATestof SmallAirCleaners,"NewShelterMagazine, RodalePress,Emmaus,Pennsylvania,July/August 1982. 6.Spingler,JohnD.,Sexton,Ken,"IndoorAir Pollution--APublicHealthPerspective,"Science Magazine,Vol.221,No.4605,July1983. 7.Tiedemann,Thomas,Brown,James,Nawrock, Paul,"MeanSolarRadiationforFloridaCities," FSEC-77-3,FloridaSolarEnergyCenter,April 1977. ChillEffectofAirMovingat300FeetPerMinute(3.4MPH) Actual Temperatures Relative Humidity Sensed Temperature Chill Effect 82degF 73% 71degF 11degF 85degF 75% 74degF 11degF 85degF 64% 72degF 13degF 90degF 65% 78degF 12degF 90degF 50% 76degF 14degF