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Should You Invest in a White Roof?

— By Kiera Butler

| Mon Feb. 15, 2010 2:00 AM PST

Common sense fashion advice: When the weather's warm, light colored clothes keep you cool. Recent studies have shown that the same is true for buildings: White roofs and roads reflect heat instead of absorbing it, reducing scorching summer temperatures in cities (cities are hotter than rural areas because of the "heat island effect")—and possibly even slowing global warming.

The latest white-roofs study used computer simulations to figure out what might happen if every roof in every city of the world were white. The finding: An average temperature reduction of .7 degrees Farenheit. Good news in general, but here’s the problem for homeowners: Since white roofs cool buildings all year round, some people have pointed out that folks with white roofs in northern climates might end up cranking the thermostat higher than their neighbors with dark-colored roofs during winter months.

Roofs of the future might solve this problem: Last year, a team of MIT researchers came up with a prototype of high-tech tiles that change color based on the air temperature. A cool idea for sure, but unfortunately the smart tiles aren't on the market yet. So till they are, should you spring for a white roof even if you live in the chilly north? Hashem Akbari, a senior scientist and leader of the Heat Island Group at the Lawrence Berkeley National Laboratory, says yes, since AC typically uses a lot more energy than heat. "The wintertime penalties are only a fraction of summertime savings."

Most of the studies so far are have focused on cities—but Akbari says that white roofs make sense for folks in rural areas and the 'burbs, too. One thing to keep in mind: Whitewashing your roof won’t cut it—for significant energy savings, the roof materials themselves have to be white. "Many roofing materials come in an assortment of colors at the same cost," says Akbari. "One can select a white rather than a dark color."