A roll-out continuous attic ridge vent has many passages for the air to flow out of the hottest part of the attic.
Question: Even though I think my house is adequately insulated, my air conditioner runs a lot in the summer. On sunny days, the ceiling in my upstairs bedroom seems hot, so I assume heat is coming from the attic. How can I reduce this heat flow?
Answer: Adequate attic insulation is only one aspect of keeping your house cool and reducing your air-conditioning costs. By “insulation,” most folks mean thermal insulation that blocks heat conduction. This includes fiberglass, rock wool, foam and/or cellulose insulation on the attic floor and in the walls.
There are three modes of heat transfer—conduction, convection and radiation. Conduction refers to heat flow typically through solid materials. This is how the handle of a metal skillet gets hot on the stove. Convection is similar to conduction, but occurs in fluids and gases. This is why you feel colder in the wind than in still air. Regular thermal insulation in your home’s walls and ceiling blocks conduction and convection heat transfer.
The third mode of heat flow—radiation— is how the sun heats the Earth and why you feel warm in front of an open fireplace. Unfortunately, standard thermal insulation is not very effective for blocking this type of heat flow. On a hot summer afternoon, a roof, especially a dark, asphalt-shingle one, gets extremely hot. This heat then radiates downward through the attic insulation and into your house.
You can tell if the ceiling is hotter than the walls just by putting the back of your hand against it in the afternoon. If it feels much warmer, this may be the major reason you’re running the air conditioning more than normal.
If your house will need a new roof soon, replace it with light-colored shingles to reduce the roof temperature. Metal roofs, particularly aluminum ones with heat-reflective paint, stay even cooler and minimize heat transfer down to the ceiling below.
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Check out these web articles for more ways to keep your home comfortable this summer, including:
“Metal roofing keeps things cool”
This bonus Energy Q&A article includes information on roofing options that reflect the sun’s heat.
South Carolina energy-efficiency experts share 11 secrets for lower power bills this summer.
“Eight energy upgrades that pay”
Regardless of the season, you’ll be more comfortable and use less electricity if you follow these simple home improvement tips.