Cool Roofs: Keeping Buildings from Baking

Cool Roofs: Keeping Buildings from Baking

1On a sunny summer afternoon, step barefoot onto a dark parking lot and then onto a light sidewalk. You will feel a big difference! The same idea can help keep buildings cooler. Many builders and scientists think more buildings should have cool roofs, which are roofs that are white or another light color.

2First, light colors stay cooler in the sun than dark colors. Light colors reflect, or bounce back, much of the sunlight that hits them. Dark colors absorb, or soak up, more sunlight and turn it into heat. You can test this yourself. Lay a black sheet of paper and a white sheet of paper in the sun for an hour. Then touch them. The black paper will feel warmer.

3Cool roofs also keep the rooms below them cooler. On a hot day, a dark roof can get much hotter than the air around it. That heat moves down into the top floor of the building. A light roof does not heat up as much, so less heat moves inside. People who live or work under a cool roof stay more comfortable.

4Cool roofs can also save energy. When a building stays cooler, its air conditioners do not have to run as long. Using less air conditioning means using less electricity. That can lower the power bill for a family or a school.

5Finally, cool roofs may help a whole city. Cities are often warmer than the countryside around them, especially at night. One cause is that dark roofs and roads soak up heat all day and give it off after the sun goes down. Some cities have started programs that coat many rooftops white to fight this problem.

6Cool roofs cannot solve every problem that hot weather brings. Still, a light-colored coating on a roof is a simple way to make a real difference on a hot summer day.