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s .92 N7vye Your ntilating 1921 Energy-Efficient Home Montana Departmentof Natural Resources and Conservation Fora list of otherfree publications about saving energy at home or atwork, contact: Montana Department of Natural Resources and Conservation 1520 East Sixth Helena, MT 59620-2301 Phone: 444-6697 This booklet was reprinted with permission of the Alberta Department of Energy in July 1991. Itwas adapted to Montana requirements by Paul Tschida, Brian Green and Pat Hoban of the Department of Natural Resources and Conservation and Bill Jelllson, chief. Mechanical Safety Section, Building Codes Bureau, Department of Commerce. Ventilating Your Energy-Efficient Home Free from Montana Department of Natural Resources and Conservation 1520 East Sixth, Helena, MT59620-2301 Phone; 444-6697 Digitized by the Internet Archive in 2017 with funding from Montana State Library https://archive.org/details/ventilatingyoure1991 mont Table of Contents INTRODUCTION 2 UNDERSTANDING NEWTERMINOLOGY 4 VENTILATION CONCERNS 5 Humidityand Odors 5 IndoorAirPollutants 6 Identifying the Problem 6 Solutions 8 Backdrafting 9 Identifying the Problem 9 Solutions 11 CHOOSING AVENTILATION SYSTEM 12 PassiveSystems 13 Exhaust-OnlySystems 14 Heat RecoveryVentilators 16 HowTheyWork 16 System Design 17 Controls 18 Selection and Installation Guidelines 20 SUMMARY 21 1 Introduction In the past, bringing fresh airindoorswas notaconcern. Most houses received enough fresh airby natural airleakage.Today, however,that attitude ischanging.Two importanttrends have led toaconcern aboutadequateventilation: • Since 1974, fuel prices have increased significantly. In an effortto reduce heating bills, homeowners have been reducing airleakage byadding insulation, weatherstripping doors and windowsand sealing cracks in the building envelope. ' • In the past fiveyears, advances in residential construction techniques have meantthat new homesarewell sealed and have higherinsulation levels. Also, new higherefficiency heating systems reduce airleakage by reducing chimney losses. Air-sealing techniquesand special construction methods have successfully reduced heating billsand increased comfort. However, tightlysealed homes may result In unsafeoperation of combustion appliances, condensation problems, or concentrationsofaircontaminantsthat may Impairhealth or causediscomfort. Most tightly-built new homes in Montanaareelectrically heated, but It is possibletosafely Install combustion heating systems and appliances(wood, natural gas, propaneorfuel oil) in tighl homes.The MontanaDepartmentof Natural Resourcesand Consen/atlon recommendsthatsealed combustion furnaces, wood stoves and appliances be used In tight new homes; these furnaces, wood stovesand appliances havetheirown direct outdoorcombustion airsupplies sotheywon’tdraw indoorair from the houseforburning. Fireplaces should also havetheir own direct outdoorcombustion airsupplies. ChapterSixof “The Uniform Mechanical Code,” which is in effectthroughout Montana, coverssafe installationsofcombustion furnacesand appliances. Ifyou should have questions about safety, contact yourlocal building codeofficial orthe MontanaBuilding Codes Bureau, 1218 East Sixth Avenue, Helena, MT59620, phone 444-3933. 2 Although poorairqualityand inadequateventilation are not widespread,there is nowagreaterpotential forsuch problems. The purposeofthis booklet isto increaseyourawarenessof ventilation and to helpyou identifyany potential orexisting problems In yourhome. These problems can be solved bycarefullycontrollingthe movementof indoorand outdoorairwithin the house environment.Theexchangeofindoorandoutdoorairiscalled ventilation.Theterm naturalventilation Is used todescribeair exchangeoccurring withoutthe useof mechanical devices.This could bethrough unintentional openings(such as airleakage through cracks in the home)orthrough intentional openings (such asoperablewindowsorfresh airducts). Mechanical ventilation referstoairexchangecreated byelectricfans. Atticventilation will not bediscussed in this booklet as itdoes not significantlyaffectthe indoorairquality. 3 New Understanding Terminology This section describesterms used in this booklet(Figure 1). Air Change Rate The rateat which airinsidethe house is replaced byoutside air through acombination of natural and mechanical ventilation. Forexample, an airchange rateofone-halfairchange perhour (ACH) meansthat halfthevolumeofairin the house is exhausted and replaced byfresh aireach hour. Circulation Air Indoorairthat is moved around the house byacirculating fan as in forced airheating systems. Combustion Air Theairrequired toensureefficient and safeoperation of combustion appliancessuch asfuel-fired furnaces, water heatersand fireplaces. Dilution Air Theairrequired bysome combustion heating systemsto safeguard the heaterfrom pressurefluctuations in theflue and to maintain an effectivechimneydraft. Exhaust Air Airexpelled outdoors by bathroom and kitchen fans, clothes dryers, powervacuums, etc. Exfiltration The uncontrolled leakageof indoorairout ofthe housethrough cracksaround windows,doors, electrical outlets and through otheropeningssuch asthechimney. Infiltration The uncontrolled leakageofoutdoorairintothe housethrough cracks around windows,doors, electrical outlets and other openings. Replacement Air Outdoorairthat replacestheairremoved from the house by dilution air,exhaust airand exfiltration. It is usuallysupplied by fresh airinlets intentionally installed in the homeorby infiltration. E^flLTmiOM IMRL'nRtqiOW AIK Eyv4AO?>T AIK Ventilation Concerns Humidity and Odors Humidityand odorscan beannoying and asourceofdiscomfort when present in excessiveamounts. Overtime, high indoor humiditycan cause serious structural problemswith wood rot and damagetootherbuilding materials.When odors lingeror excessivecondensation accumulateson windows, it isan indication thatyourhome may not be receiving an adequate supplyoffresh air. Solutionsto moisture problems aredetailed in Moistureand Home EnergyConservation, anotherfree publication available from DNRC. Alwaystrythe simple stepsfirsttosolve condensation problems.Theyare usuallythe lowest cost actions. It is important to understand that homeswith condensation problemsdo not necessarily haveaventilation problem.There areothercausesforcondensation besides lackofventilation, such as inadequate insulation orpoorweatherstripping. Conversely, solving acondensation problemdoes not Implythat there is noventilation problem. 5 . IndoorAir Pollutants Identifying the Problem Ourindoorenvironment haschanged. Questionsare now being raised aboutthe possibleadverseeffectsof lowerairleakageon Indoorairqualityand the health ofoccupants.A numberof factorscan cause indoorairquality problems; • Sourceswithin the house maycreate high pollutant levels. • Ventilation maybe insufficientto removethe pollutantsthat are generated. • Pooraircirbulation can result in localized areasof high pollutant concentrations. The indoorenvironment can be contaminated in avarietyof ways. Radon can enterthe housefrom surrounding soil or groundwaterorbeemitted from certain masonry building products. DNRCofferstwofree publicationson radon. Formaldehydeand benzopyreneare produced indoors by wood-burning appliancesorgiven off by building materialsand furnishings. Otherpollutants, such astobaccosmokeand chemicalsfrom cleanersand aerosols, areadded bythe occupants(Figure2). Carbon monoxidefrom incomplete combustion orimproperlyoperating combustion devicescan createaserious health hazard. Someofthesourcesand health effectsoftheseand otherpollutantsaredescribed inTable 1 Figure2