Ask the expert

Even if your attic is well-insulated, other spots in your house could be leaky enough that you’re helping heat or air-condition the great outdoors, not just your home.
Even if your attic is well-insulated, other spots in your house could be leaky enough that you’re helping heat or air-condition the great outdoors, not just your home.

— During the periods of low temperatures this winter, it became apparent that our house was letting cold air get in — even though our attic is well insulated, doors weather-stripped and windows caulked. Any ideas on what could be causing this and what to do about it? I know it means the same thing will be happening in reverse come hot weather.

We’re glad you’ve done a good job with insulation, weather-stripping and caulking, but cold air can seep in (or out, when you’re using air conditioning) in sneaky ways.

For hgtvpro.com, Kara Wahlgren offered some tips on where to look for additional leaks, plus an idea of whether you can solve the problem or if it’s wisest to call in a professional.

“Even the smallest leak can rack up a big energy bill,” Wahlgren says. “While many homeowners are aware of the benefits of weather-stripping doors and windows, they may overlook other common sources of air leaks. Seal these often-undetected spaces, and homeowners could see a huge difference in their energy expenditures.”

Here’s her advice:

Culprit: the fireplace. Chimneys are designed to let hot air escape from the house, and they do an excellent job — even when there’s no fire going. When the fireplace isn’t in use, keep the flue closed to prevent air from escaping. Consumers can also buy chimney balloons that inflate to fit beneath the flue, preventing air from escaping. It deflates automatically when it comes into contact with heat.

In the attic, check for gaps around the chimney. Building codes require combustible materials like insulation to be 2 inches from a masonry chimney, so you may need to have built a metal dam around the chimney for clearance. Seal with aluminum flashing and heat-resistant caulk.

Skill level: professional. Chimney work is wrought with tricky codes and potential fire hazards, so weekend warriors should generally steer clear.

Culprit: vents. Dryer vents and exhaust fans can whisk conditioned air out of a home and let outside air in. In homes with a kitchen exhaust fan, add a magnetic cover to prevent air from leaking in or out while the fan isn’t in use.

Bathroom exhaust fans should have an internal flapper damper to prevent air from coming in or out when the fan is off. Dryer vents typically have a flapper to reduce air leaks, but if the vent becomes clogged with lint, it can prevent the flapper from working properly. Check vents periodically to make sure they’re free of lint, or install a dryer vent seal.

Skill level: professional. There are risks in making a home too airtight. It can limit the air supply for heating appliances, and exhaust fans may pull combustion gases into the living space. A professional contractor can ensure there’s adequate ventilation to prevent such dangerous “backdrafting.”

Culprit: the attic. Check for air leaks around plumbing pipes, furnace flues and electrical junction boxes. Gaps around plumbing pipes can be filled with expanding foam or caulk, and those around junction boxes can be caulked.

Furnace flues are slightly more challenging. Pipes need to be at least 1 inch from combustible materials such as insulation, so seal with heat-resistant caulk and build a metal dam around the flue to prevent insulation from touching the hot pipe. Finally, determine whether or not the attic entrance is properly sealed by turning on the attic light at night and closing the door or hatch. If you can see light, use weather-stripping to prevent air from escaping through those gaps.

Skill level: it depends. Novices can handle the weatherstripping, but sealing around hot pipes should be left to professionals familiar with building codes.

Culprit: the electrical system. Electrical outlets and switch plates can allow air to seep through the walls. Find leaks by waving a burning incense stick or a damp hand in front of the outlet cover; you’ll be able to see the smoke waver or feel any drafts on your hand. The Department of Energy recommends installing foam gaskets behind outlet covers and switch plates to prevent air from coming through.

Skill level: novice. Turn the breaker off in the area where you’re working.

Culprit: the extras. Add-ons like recessed lighting, mail slots and wall air-conditioning units may add convenience and comfort to a home, but they also add the potential for air leaks. Caulk any gaps around mail slots, and seal around leaky light fixtures. If the insulation above a recessed light seems dirty, it’s probably allowing air to escape. Remove window air-conditioning units before winter.

Skill level: it depends.

Novices can caulk gaps and remove window units, but only a professional should seal around recessed lighting due to potential fire hazards.

Locating and sealing such air leaks can go a long way in reducing energy costs.

HomeStyle, Pages 33 on 02/19/2011

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