For your home to be green, you need a high-efficiency furnace, not to mention high-efficiency appliances and windows. Reality:
It doesn't matter how efficient your furnace is if it's heating the outside of your house.
Sure, new equipment will save energy, says Lane Burt, a building-energy expert with the Natural Resources Defense Council, but it's better to first go low tech.
Hire a professional to find all the leaks in your home and plug them up. That can be done in most homes for anywhere from a few hundred to a few thousand dollars -- less than most new heating systems.
"It completely changes the way the home operates," says Burt. "Your old furnace will actually work better." Not only that, but when it comes time to buy a new one, you may find that a smaller (and therefore less expensive) furnace will do. -- E.F. NEXT: Climate: Offsetting carbon dioxide