Holes for sewer and water lines, exhaust vents, and cable and phone lines are typically rough cut and uninsulated, so warmed or cooled air from inside your house escapes and outside air seeps in. How to spot it:
Use a handheld infrared thermal leak detector, such as Black & Decker's TLD100 ($49.99; blackandecker.com
). Pass the device over the solid wall near the hole, then the hole itself. If you see a significant difference in temperature, you've got an air leak. How to stop it:
Fill minor gaps of less than ¼
inch with silicone caulk. For larger voids up to 1 inch wide, use expanding polyurethane foam insulation. The long applicator straw on cans of spray-foam sealants, such as Great Stuff, are particularly handy for accessing hard-to-reach areas inside sink vanities and behind heavy washers and dryers. "If you're dealing with a gap near a combustible device, like a fireplace, make sure you're using products approved for high temperatures," says Brown. The payoff:
Prevent 17 percent of treated air from escaping your home by sealing gaps around exterior penetrations.