The places where cold air infiltrates in winter are routes for hot air in summer. And what's worse, hot air is often accompanied by high humidity, making you even more uncomfortable. Armed with a flashlight, exterior-rated silicone caulk and a couple cans of expanding foam insulation, hunt down and seal all leaks. Concentrate on the attic, basement and crawl space; pay close attention to anything that passes through a ceiling or wall, such as ductwork, electrical or plumbing conduits and kitchen and bath vents. Other common leaky spots are around windows and doors. If you can rattle a window, it's leaking. Seal it with weather stripping.
Cost: $6 to $25
Benefit: Up to 10 percent off your cooling bill