Image courtesy of the National Renewable Energy Laboratory

Popular Science tells us about a new study from the Department of Energy on a relatively cheap and easy way to save energy costs and help combat global warming: painting roofs white, or at least a cooler color than black. This isn't a brand-new idea, but the good folks at Lawrence Berkeley National Laboratory have made some calculations about just how much potential there is there:

The researchers extrapolated a roof's CO2 offset over its average lifespan. If all roofs were converted to white or cool colors, they would offset about 24 gigatons (24 billion metric tons) of CO2, but only once. But assuming roofs last about 20 years, the researchers came up with 1.2 gigatons per year. That equates to offsetting the emissions of roughly 300 million cars, all the cars in the world, for 20 years.

Pavement and roofs cover 50 to 65 percent of urban areas, and cause a heat-island effect because they absorb so much heat. That's why cities are significantly warmer than their surrounding rural areas. This effect makes it harder -- and therefore more expensive -- to keep buildings cool in the summer. Winds also move the heat into the atmosphere, causing a regional warming effect.

Energy Secretary Steven Chu, a Nobel laureate in physics (and former Berkeley Lab director), has advocated white roofs for years. He put his words into action Monday by directing all Energy Department offices to install white roofs. All newly installed roofs will be white, and black roofs might be replaced when it is cost-effective over the lifetime of the roof.

I'm guessing conservatives will attack this idea, because ... well, because conservation is for wimps, or something. You might remember that Jimmy Carter put solar panels on the roof of the White House, and when Ronald Reagan took office, he ordered them taken down. I wonder if President Palin will demand that all the white roofs on DoE buildings be painted black?

-- Paul Waldman

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