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Hearth & Home

Domestic Security

Lower the earth’s temperature and your energy bills

by Barry Chalofsky

Does your living room feel like an arctic wilderness in the winter? Are your windows drafty, hard to open, and covered with frost on chilly mornings? Can you see daylight around your door edges? Maybe it’s time for a few ecofriendly changes to your home that will let the sunshine in but keep the cold out this winter.

While homeowners often hear that adding insulation to their walls and attic will seal the deal on energy efficiency, in fact as much as 40 percent of a building’s heat loss is through the windows and doors. Repairing or replacing these faulty fixtures can significantly reduce that loss.

The array of options can be daunting, but decoding the mysteries of energy efficiency is easier than you think. If your windows and doors are relatively new and in reasonably good condition, for example, you can probably get by with some low-cost repairs. One simple step is to replace weather stripping around doors, especially along the bottom, with material flexible enough to form a good seal in all temperatures. With windows, the compound that holds the panes in the frame is as important as the view. If the caulk is cracked or missing it lets cold air in, but you can repair it without needing to buy a whole new window. Adding insulated shades or drapes with reflective backing will further reduce drafts.

If your windows and doors are too far gone to fix, new energy-efficient replacements are available. When shopping, check the labels. The National Fenestration Rating Council (NFRC) has developed a window-energy rating system that helps consumers compare products. The NFRC labels are also used on door and skylight products that are part of the EPA’s Energy Star program. (In 2001 these products, along with Energy Star appliances, reduced energy use and therefore pollution from power plants by the equivalent of 12 million cars.)

When it comes to window glazing, more layers are better. Exchanging single-glazed for double-glazed windows can save as much as $250 per year in heating bills for a 2,000-square-foot house.

Even the tiny space between the panes of glass affects energy performance; one-half to one inch is optimal. Consider windows that fill that space with gases like argon, krypton, or a mix of the two. For about $10 more, an argon-filled window loses 15 percent less heat than one filled with air.

Home improvers can also purchase windows with thin transparent coatings of silver or tin oxide—called "low-e glass" (the "e" stands for "emittance"). These coatings permit light to pass through but reflect infrared heat radiation back into the room, reducing heat loss. Low-e windows with what’s called a "high solar gain coefficient"—the amount of solar heat admitted through the glass—are better in colder climates. (The coating faces into the gap between the glass layers to block the escape of radiant heat through the window.)

It’s often best to mix and match windows. For example, you could install low-e glass with a high solar heat gain on the south side, and windows with the lowest rate of heat loss on the other sides of your home. (The measurement for low heat-loss in glass is called a U-factor; the lower the U-factor the better the insulating value.)

Choosing doors isn’t exactly open and shut but it’s less complicated than windows. The best bets are those that have a polyurethane foam core. A door with a steel or fiberglass exterior and foam-filled interior can provide more than double the insulation of a solid wood door. Old-style glass patio doors are about as energy efficient as that old family station wagon, but new patio doors have gas filling and multiple glazing, as well as tight seals and good-quality framing that keep the elements where they belong: outside.

As with any do-it-yourself project, you need to ensure proper installation. If the job seems too complicated, look for a contractor who specializes in this kind of energy-saving work. Either way, rest assured that if you make the right choices to begin with, and then take the time to install the windows and doors correctly, you won’t have to wear a parka to the dinner table, crank up the heat to stay warm, or wince when the utility bill comes.

Barry Chalofsky is author of The Home and Land Buyer’s Guide to the Environment.

For more detail, see the following sites:;; or

According to the U.S. government, as much energy is lost through poorly insulated windows and doors as we get from the Alaska pipeline each year.

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