Drafty windows create a large hole in your home's energy or thermal envelope.
In some cases, weatherstripping your windows will go a long way towards solving the problem. If you live in a cold climate but don't have double-glazed windows, you can install temporary storm windows to either the inside or outside of your regular windows to minimize heat loss in winter.
If your windows leak really badly, however, you might consider replacing them with new, modern, energy efficient ones. Window replacement can be expensive - $500 or more per window is a rough ballpark estimate - so it will take you five to ten years or more to recoup your investment from the energy savings alone. Of course, there are other benefits to replacing windows - increased comfort and a more attractive home, for example.
To find out more about replacing windows with the more efficient models available today, see the links in the bottom of the right column.
An improperly hung door, or one with gaps between the door jam and the door itself can let in lots of cold winter air, or allow cool airconditioned air to leak out in summer.
It's estimated that up to 11 percent of the air leaks in a building are around the doors. In most cases, weatherstripping around your doors will fix most of the problems.