Stop the Leaks
Air infiltration is the single highest cause of energy loss in homes, and stopping the leaks is an inexpensive way to reap huge savings. A day or two spent caulking, weather-stripping, crack sealing, and insulating will make a home more comfortable and energy efficient.
Caulk around windows and doors, at siding joints, where different materials meet, and any other places where you think infiltration might be a problem. In colder regions, homeowners sometimes apply vinyl sheeting over windows to reduce the chance of air entering; these can either be applied on the interior or exterior.
Doors can be weather-stripped with a variety of materials and varying degrees of difficulty. Newer doors have a rubber seal that fits in a small groove in the door jamb. When damaged these can be easily replaced. There is also adhesive foam weather-stripping that can be applied around leaky doors and windows.
An area often overlooked is the basement. Poorly sealed and insulated basements create drafts, cold floors and increased energy costs. Check where wood meets concrete or concrete block and make sure all joints are well-sealed. Apply insulation in framed wall cavities, under flooring, or both. In crawlspaces, insulate under flooring and make sure all exposed earth is covered by a thick layer of polyethylene, lapped and secured in place.
Finally, visit energy.gov, the website for the Department of Energy, for more helpful tips and ideas.