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

Then-U.S. Energy Secretary Spencer Abraham touts the benefits of installing proper insulation at a Home Depot store in 2003. See more pictures related to green living.
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­In autumn and spring, mild temperatures make it easy to forget about your home's energy efficiency. But when your air conditioner or furnace kicks in during summer and winter, the energy wasted heating and cooling your home becomes painfully obvious. It can hit your bottom line hard, especially due to the price spikes in electricity and gas during the most extreme months. As the demand for electricity, gas and heating oil increases, so, too, do the prices for these commodities.­

Homeowners have ways of beating the utility companies by taking steps to make their homes more energy efficient. There are plenty of options to make your home "greener," but what's the best way to dramatically lower the energy use in your home? It turns out that the improvement that produces the most significant result is also the cheapest.


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­A lack of insulation often accounts for the biggest amount of energy loss in the average home. Heat escapes from homes during the winter and intrudes during the summer through­ a house's envelope. This envelope consists of all the ceilings, floors, outer walls, windows and doors in your house. Simply by sealing this envelope, you can decrease your heating and cooling costs by an average of 20 percent [source: Energy Star].

As if that weren't enough, some countries offer extra financial incentives to their citizens for making their homes energy efficient. In the United States, residents can get up to a $500 tax credit on efficient doors, $200 on windows and as much as $2,000 on a solar water heater [source: USA Today]. Canada is spending $300 million over four years on grants to energy-saving residents. The average grant is around $1,000 per homeowner [source: The News Room]. And the European Union is in talks for reducing taxes associated with energy-efficient fixtures.

So how do you determine if your envelope needs sealing, and, if it does, what's the best way to do it? The United States Department of Energy and the Environmental Protection Agency's joint Energy Star effort suggests you start by doing a simple inspection of your home. Since most of the temperature exchange in a home takes place in the attic and basement, these are good places to begin.

In the attic, examine your current insulation. Does it look like it's seen better days? Perhaps it's time to replace it, but before you do, inspect your old insulation. Look for dirty spots, as well as frost-covered spots (if it's winter) or wet spots (during summer). All of these are indicators that air is passing through the insulation. Pull it back, and you'll most likely find some holes to fill. Also take a look at the area where the roof meets the tops of your house's walls. Are there gaps where air is coming in from the outside? Be sure to inspect any pipes leaving the home through the attic walls or the roof, including your furnace flue -- the duct that carries exhaust outside -- chimney and plumbing. Are there gaps around them?

In the basement or crawlspace, inspect the area where the foundation of the house meets the bottom of the walls above. Look for gaps, and, like in the attic, look for spaces between the foundation and walls where pipes and ducts leave the basement. Also pay attention to the rim joists -- the wood or concrete columns that support the floor above. Are there gaps present?

By now you've probably found some areas in your house that could use some attention. Read the next page to find out how to fix them.­



Sealing Your Envelope

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.


Lots More Information

Related HowStuffWorks Articles

­More Great Links

  • Block, Sandra. "Bill Gives Breaks to Home Improvers, Hybrid Buyers." USA Today. August 1, 2005. http://www.usatoday.com/money/perfi/columnist/block/2005-08-01- breaks_x.htm
  • "ecoEnergy Initiative: Using Less, Living Better." The News Room Canada." Februrary 8, 2007. http://www.nrcan-rncan.gc.ca/media/newsreleases/2007/200704a_e.htm
  • "Home Improvement: Improve Your Home's Energy Efficiency With Energy Star." Energy Star. http://www.energystar.gov/index.cfm?c=home_improvement.hm_ improvement_index