Cool Roofs...
· Increased need for heating in winter. During winter months, cool roofs increase the need for heating energy in cold climates. However, in winter the sun stays low, the days are short, and the skies are often cloudy, limiting the amount of sunlight available to a roof. A study conducted by the Heat Island Group shows that in the United States, this winter heating penalty is typically small compared to the summer cooling benefit. (Additionally, note that if a roof is covered with snow, the color of the roofing product doesn't matter — the roof's surface will be white.)
· Glare. Glare from a bright white or silvery roof on a low-rise building may disturb occupants of taller neighboring buildings. In this situation a cool-colored (nonwhite) roof may be more appropriate for the shorter building.
· Increased need for heating in winter. During winter months, cool roofs increase the need for heating energy in cold climates. However, in winter the sun stays low, the days are short, and the skies are often cloudy, limiting the amount of sunlight available to a roof. A study conducted by the Heat Island Group shows that in the United States, this winter heating penalty is typically small compared to the summer cooling benefit. (Additionally, note that if a roof is covered with snow, the color of the roofing product doesn't matter — the roof's surface will be white.)
· Glare. Glare from a bright white or silvery roof on a low-rise building may disturb occupants of taller neighboring buildings. In this situation a cool-colored (nonwhite) roof may be more appropriate for the shorter building.
On a summer afternoon, the black roof at left was measured to be 30ºC (54ºF) warmer than the white roof at right. (Image courtesy of the U.S. Department of Energy)
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