Nearly 30 years have passed since the first oil crisis gave Americans an indelible lesson in energy deprivation. Yet many homeowners still don't realize how much energy seeps out of their houses every day despite the steps they might have taken. According to experts, many homes — including new ones — act more like sieves than like sealed buildings. "What we've learned about basic energy efficiency isn't readily available to homeowners, builders and contractors," says Dave Brook, an extension agent specializing in energy for Oregon State University.

The reason is clear enough: Because much of that knowledge was developed for low-income housing as part of the federal Weatherization Assistance Program, it hasn't yet reached the mainstream housing industry. Nevertheless, it includes a number of findings that affect all homes.

For example, because hot air rises, most heat lost in a building goes right through the roof. What causes that heat loss? Leaks in attic floors are the culprit, lowering the R-value of attic insulation and draining 30 to 50 percent of a home's heating energy. And while leaks around windows and doors let out far less energy than you probably thought, gaps in forced-air ducts can cut home heating and cooling efficiency 40 percent.

Fortunately, making your home more energy efficient isn't rocket science. A couple of weekends sealing the attic and furnace ducting using materials that cost less than $50 on average will slash up to 30 percent off your energy bill.

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