www.desatech.com 5117001-01EAIR FOR COMBUSTION AND VENTILATIONUnusually Tight ConstructionThe air that leaks around doors and windowsmay provide enough fresh air for combustionand ventilation. However, in buildings of un-usually tight construction, you must provideadditional fresh air.Unusually tight construction is defined asconstruction where:a. walls and ceilings exposed to the outsideatmosphere have a continuous watervapor retarder with a rating of one perm(6 x 10-11 kg per pa-sec-m2) or less withopenings gasketed or sealed andb. weather stripping has been added onopenable windows and doors andc. caulking or sealants are applied to areassuch as joints around window and doorframes, between sole plates and floors,between wall-ceiling joints, between wallpanels, at penetrations for plumbing, electri-cal and gas lines and at other openings.If your home meets all of these three criteria,you must provide additional fresh air. SeeVentilation Air From Outdoors, page 7.If your home does not meet all of the threecriteria above, proceed to Determining Fresh-Air Flow For Heater Location, page 6.Confined and Unconfined SpaceThe National Fuel Gas Code, ANSI Z223.1/NFPA 54 defines a confined space as a spacewhose volume is less than 50 cubic feet per1,000 Btu per hour (4.8 m3 per kw) of the ag-gregate input rating of all appliances installedin that space and an unconfined space as aspace whose volume is not less than 50 cubicfeet per 1,000 Btu per hour (4.8 m3 per kw)of the aggregate input rating of all appliancesinstalled in that space. Rooms communicatingdirectly with the space in which the appliancesare installed*, through openings not furnishedwith doors, are considered a part of the un-confined space.* Adjoining rooms are communicating only ifthere are doorless passageways or ventilationgrills between them.WARNING: This heater shallnot be installed in a confinedspace or unusually tight con-struction unless provisions areprovided for adequate combus-tion and ventilation air. Read thefollowing instructions to insureproper fresh air for this andother fuel-burning appliancesin your home.Today’s homes are built more energy efficientthan ever. New materials, increased insulationand new construction methods help reduceheat loss in homes. Home owners weatherstrip and caulk around windows and doorsto keep the cold air out and the warm air in.During heating months, home owners wanttheir homes as airtight as possible.While it is good to make your home energyefficient, your home needs to breathe. Freshair must enter your home. All fuel-burning ap-pliances need fresh air for proper combustionand ventilation.Exhaust fans, fireplaces, clothes dryers andfuel burning appliances draw air from thehouse to operate. You must provide adequatefresh air for these appliances. This will in-sure proper venting of vented fuel-burningappliances.PROVIDING ADEQUATEVENTILATIONThe following are excerpts from National FuelGas Code, ANSI Z223.1/NFPA 54, Air forCombustion and Ventilation.All spaces in homes fall into one of the threefollowing ventilation classifications:1. Unusually Tight Construction2. Unconfined Space3. Confined SpaceThe information on pages 5 through 7 will helpyou classify your space and provide adequateventilation.