Why a White Roof Is a Cool Roof, for the Planet and Your Pocketbook

Image Gallery White roof coatings can reduce air conditioning energy use by as much as 20 percent in hot, sunny weather. NREL/CRAIG MILLER PRODUCTIONS/DOE

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Most of us know better than to wear black on a hot day, but when it comes to the roofs on our houses, the aesthetics of black take priority. That is, until temperatures rise and we find ourselves cranking the air conditioner, with our electric bills following suit. The good news is you can save money by lightening the color (and therefore the temperature) of your roof, or switch to a white roof the next time your house needs a new hat. Also, white roofs, aka cool roofs, are a “hot” topic these days as a means to help stem global warming.

The Benefits of a White Roof

Switching to a white roof can actually reduce energy use by about 20 percent in hot, sunny weather, according to the Lawrence Berkeley National Laboratory Heat Island Group. According to Heat Island Group lead scientist Hashem Akbari, transitioning to reflective roofing (and pavements) in the world’s urban areas would offset the equivalent of emissions from the planet’s 600 million cars for the next 18 years. In addition, a 1,000-square-foot white roof saves air conditioning use that otherwise would emit about half a ton of carbon dioxide per year. (The average total square footage of a home in the United States is more than 2,000 square feet.) Over the 20-year life of the roof, that stacks up to 10 tons less carbon dioxide emissions.

When the Heat Island Group recorded data on a commercial building in Davis, Calif., they found that installing a white roof caused an 18 percent drop in their average electricity use for air conditioning. In urban areas, white roofs help lower locally increased temperatures due to the large proportion of paved surfaces, which results in reduced smog levels. The list of benefits for white roofs goes on and on.

“This will not be the silver bullet that solves the global warming problem, but it cools your home, helps cool the globe and puts money in your pocket,” Akbari says.

Critics have suggested white roofs do more harm than good in northern climates. But research shows that the heating benefits of a dark roof in the winter are negligible because days are shorter, skies are cloudier, the angle of the sun is low and sometimes roofs are covered in snow. And there isn’t much negative impact with a white roof in areas where air conditioning is in use at least part of the year.

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