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What's the one thing you can do to your home to save the most energy?


Sealing Your Envelope
Assuming your attic doesn't look like this, you could have your home's envelope sealed with a weekend's work.
Assuming your attic doesn't look like this, you could have your home's envelope sealed with a weekend's work.
Christopher Simon Sykes/Hulton Archive/Getty Images

You might think that those drafts you feel near your doors and windows are the biggest threats to your heating and cooling bill. But don't forget the parts of your hom­e you visit less often. While upgrading to energy-efficient windows and weather-stripping your doors is a good idea, it's those gaps you found in the attic and basement where most of your home's energy escapes.

So how do you fix all of the problems you've uncovered through your energy assessment? With just a few items from a home improvement or local hardware store, you can seal your home's envelope. Even better, with a little hustle, you could conceivably finish this energy-saving project over a weekend.

­Back up in the attic, you'll want to peel back your old insulation and fill the large gaps you found with latex expanding foam sealant. Twelve-ounce cans of this sealant are usually available for around $5, and can be found at any home improvement store. This foam expands to fill and gaps, and allows your insulation to do its job. You can use exterior caulk for smaller holes.

The gaps around those pipes that lead outside can also be filled with foam, but be sure to first figure out what kind of pipes you're dealing with. Furnace flues get very hot. To fill a gap around a flue, use aluminum flashing and special high-temperature caulk. Leave a couple inches between your flue and any fiberglass insulation. Build a barrier between the fiberglass insulation and the flue using the flashing. This will cut down on the possibility your flue will burn your insulation.

You'll also want to spray foam and insulate around any vents or ductwork in the attic roof. And attic doors or overhead hatches should be weather-stripped. If you choose to replace your old insulation, insulate the attic side of the door or hatch as well. Install insulation on the floor of the attic, as well as between the roof's joists -- the studs that hold it up.

With your attic sealed, head on down to the basement. Be sure to bring your trusty expanding foam sealant and caulk. As in the attic, fill any large holes you find in the basement with expanding foam, and use caulk for smaller holes. Apply foam around any exposed window sills, as well as around any duct work and pipes leading out of the basement. This includes pipes and ducts that remain in the house, not just ones that lead outdoors.

Even if you don't see any cracks or gaps around the rim joists that support the house above, it's still a good idea to use foam or caulk where they meet the ceiling and floor. If your basement is unfinished, work will go a lot faster, since you have easy access to all of the gaps in the exterior. But once you've finished foaming and caulking, it's not a bad idea to install fiberglass insulation between the exposed studs inside the exterior wall. This may also provide extra incentive to eventually finish your basement, and will give you a good first step toward completing the project later on.

So your envelope is now sealed. With this as a start, you can move onto other, more in-depth projects like changing out your doors and windows with energy-saving replacements. Or you could just kick back and enjoy your home's improved climate -- and, of course, that extra money you'll save.

For more information on saving home energy, visit the next page.