Exterior vents, particularly those for a clothes dryer or a whole-house fan, allow heated air to seep out of your house, while letting cold outside air in. HOW TO DO IT:
Swap your dryer's louvered or metal flapper-style vent for a Dryer Vent Seal (About $20; Battic Door
), which consists of an elbow pipe topped with a plastic cap and shuttle. When the dryer is in use, the floating shuttle beneath the hood rises to let warm air, lint, and moisture escape. When not in use, the shuttle drops down to seal the hole and prevent drafts. For a whole-house fan, construct a simple box-shaped cover out of rigid foam insulation (use foil-type duct tape for the seams) to enclose the fan during cold months, when it's not in use. From inside the house, fit the cover over the fan, and secure it to the frame with adhesive-backed Velcro strips. Just remember to remove the cover before you switch on the fan come spring. This kind of DIY cover can also help insulate in-wall or window air-conditioning units that are left in year-round. THE PAYOFF:
Vent sealing can prevent 4 percent of your home's heated air from escaping.