Save money by avoiding being caught in the draft

Inspector's Eye

October 21, 2001|By Dean Uhler

If your house isn't particularly energy-efficient, the first cold, windy weather of the season can start you thinking about ways to change the situation. One way to gain some improved efficiency is to reduce drafts. Although drafts are not the only way you lose heat, they are a significant factor.

Houses lose heat in essentially two ways. One way is transmission of heat through the exterior envelope of the house. This has the dominant source of heat loss historically. But transmission loss is drastically reduced by thermal insulation, increasingly used in houses in the past 50 years or so.

The other source of heat loss is air movement in and out of the house, through infiltration, "exfiltration" and ventilation.

Ventilation is not a problem. It is the intentional, controlled flow of air into and out of a house, and can be used as needed to remove excess moisture, heat, odors and general stuffiness.

In contrast, infiltration and "exfiltration" are the uncontrolled leakage of air into and out of a house through gaps and cracks in the building envelope - essentially, drafts.

Thirty percent of a home's heating and cooling costs can result from infiltration and exfiltration, according to the U.S. Department of Energy, so sealing air leaks can be a worthwhile improvement.

Although many of the air leaks that allow infiltration and exfiltration to occur are hidden and inaccessible once construction of the house is complete, some leaks can be corrected at any time.

Windows and doors are obvious targets, but reducing air flow into the attic and through floors is at least as significant, if not more so. That is because of the "stack effect" in houses, in which warm air leaks out the top of the house as cold air leaks in at the bottom, just as smoke rises up a chimney.

Ductwork and plumbing chases, leaky recessed light fixtures, wire penetrations and retractable attic stairs form potentially leaky connections between the attic and the heated space. Major leak sites in the floor include openings below the tub drain and at the numerous plumbing, ductwork and wiring penetrations through the floor decking and bottom plates of walls.

For retractable attic stairs, install a rigid foam cover kit and make the stairs airtight using latch bolts and rubber weatherstripping.

For attic hatches, insulate the top of the cover with at least two inches of rigid foam insulation or a 6-inch fiberglass batt, and seal the hatch with weatherstripping. Use the same method at attic kneewall access doors, and include a tight latch.

Seal accessible electrical, plumbing, and HVAC penetrations between any heated and unheated spaces (e.g., at the attic floor and basement ceiling), using caulk or spray foam space filler. Do not use spray foam or other combustible material around furnace flues or recessed lights; have a qualified contractor install sheet metal covers instead.

For whole-house fans, fabricate a cover from rigid foam insulation and contact paper, and attach with Velcro or a wood frame bolted to the ceiling. If the attic has easy access, build a cover from rigid foam or duct board and fasten it over the top of the fan, or hold the cover down with something like your old croquet set.

Inspector's Eye

Dean Uhler has been a home inspector for more than 12 years and is president of Baltimore-based Boswell Building Surveys Inc. Uhler is a member of the American Society of Home Inspectors (ASHI) and is the treasurer of the Greater Baltimore Chapter of ASHI.

Questions, with name, address and daytime telephone number, about homes and home inspections can be faxed to 410-783-2517, e-mailed to real.estate@baltsun.com or mailed to Inspector's Eye, Second Floor, 501 N. Calvert St., Baltimore, Md. 21278-0001.

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