Are There Passive Solar Energy Techniques For Homes In Southern Climates?

Are there passive solar energy techniques for homes in southern climates? Overhangs, awnings and shade are best for hot climates to keep the sun's heat from entering your home. Frederick Bernard, the owner...

Frederick Bernard, the owner of Acorn Builders, a custom home designer, builder, and remodeler, answers, "Yes, in a sense, but it wouldn't necessarily be called 'solar' because you would be trying to eliminate the sun from putting the heat energy into your dwelling." One of the most common passive techniques for keeping heat energy out is to use overhangs to shade windows.

According to the U.S. Department of Energy, on its Energy Efficiency and Renewable Energy (EERE) website, when you use overhangs, it's important that they be the right size. There is no such thing as one-size-fits-all when it comes to overhangs. What the best size will be depends on the climate, which means that with respect to designing overhangs, passive solar energy techniques will be different for homes in northern and southern climates. "Guidelines acceptable for the high plains of Montana are unlikely to work for a site in Florida," the EERE website says.

Bernard says, "In Austin, we use big overhangs--two feet minimum, up to three or four foot overhangs--or even patios and verandas around the house to shade the sun and prevent the heat from coming inside the house without eliminating the free light that you get from the sun."

Other passive techniques for keeping the sun's heat out of buildings include using insulated drapes, shutters, awnings, trees, trellises, and light-colored roof shingles. . Bernard says, "The use of lighter-colored roof shingles is a way to prevent heat trapping." Many builders don't take advantage of this technique, however. "It's fashionable to have dark-colored shingles in areas that have coastal humidity blowing in because if you have condensation on your roof, it will cause mold, and mold will turn your white roof black. So the tendency is for builders to use darker-colored roofs to avoid showing that mold." But that's not necessary, Bernard says. "The true secret is to make sure that the roof line is adequately insulated so that the cool air from the inside doesn't condense water on the roof, which is what causes the mold in the first place."

Bernard explains that "cold air and humidity cause condensation, just like water on a glass. When you have a glass of ice water and it's humid, you'll get water on the outside of your glass and that comes from the air. And cold air in a humid climate will cause water to show up where it's not supposed to. Then, of course, it will mold because that's the right environment for mold to grow."

In addition to using passive techniques to keep the sun's heat from entering the house, you can also use simple passive techniques to remove heat. Bernard says, "A form of passive air conditioning would be to open your windows and let the air flow through when it's a pleasant temperature outside and let that remove the heat from your house. Another way is to make sure your attic is properly ventilated so that it doesn't trap heat up there and just make the house hotter and hotter."

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