Over the next several weeks, I plan to offer a series of green remodeling tips drawn from my book, Practical Green Remodeling: Down-to-Earth Solutions for Everyday Homes.
Homes lose most of their heat through air movement. And most houses leak a lot of air. If you do nothing else to your home, the first and most important thing to do is to find air leaks and seal them with caulk, expanding foam or weather-stripping. This is the simplest, most cost-effective thing you can do to improve your home's energy efficiency.
Now that the weather is turning colder, you can find air leaks in your home with a simple test. On a day when it is 15 to 20 dregrees cooler outside than inside, close all doors and windows and turn on all exhaust fans (usually in bathrooms & kitchens). Then run a damp hand around your door and window frames. Any place you feel a draft, that's where you need to seal.
To pinpoint drafts more accurately, light a stick of incense and hold it close to a window or door. As you move it around, being careful not to set the drapes on fire, you will see from the movement of the smoke where you have drafts. You can also buy a non-toxic smoke-pen, a small device made especially for this purpose. Just Google "smoke pen" and you'll find several online sources.
If you see drafts around the outside of the frame, where the window trim meets the wall, you can easily seal that with a tube of caulk. (Use low-VOC caulk so that you’re not filling your house with potentially harmful fumes as you seal the leaks.
If you see air movement where the window sash meets the frame, you should consider replacing the jamb liners, or adding weather-stripping. This is a little more involved than caulking, but if you are patient and a little handy with tools you can probably do this yourself in an afternoon.
Other places to look for drafts are shown in the illustration below. For more detailed instructions visit the Energy Star web site here.

