Paint the Roofs White
A low-cost, low-tech solution to fight climate change just won an endorsement from Energy Secretary Stephen Chu yesterday: paint the roofs white.
The idea is simple: Black roofs absorb most radiation as opposed to white roofs which reflect a good bit more. A two-page summary of a technical paper done by an old colleague of Chu's at the Lawrence Berkeley Laboratory and a commissioner on the California Energy Commission advances the concept:
Most existing flat roofs are dark and reflect only 10 to 20 percent of sunlight. Resurfacing the roof with a white material that has a long-term solar reflectance of 0.60 or more increases its solar reflectance by at least 0.40. Akbari et al. estimate that so retrofitting 100 m2 (1000 ft2) of roof offsets 10 tonnes of CO2 emission. (For comparison purposes, we point out that a typical US house emits about 10 tonnes of CO2 per year.)
So painting 1,000 square feet of black rooftop white can offset the emissions of a typical US household. Or in the big picture, as Chu pointed out, lightening the color of roads and roofs could have the equivalent effect of taking every car in the world off the road for 11 years.
Another booster for this idea has been Climate Progress' Joe Romm who wrote about the concept earlier this year and again today after Chu's comments.
California has been requiring this option for building owners since 2005, justified solely on energy efficiency gains. With carbon offsets for efficiency, there's also a possibility for owners to make money on the switch by monetizing the carbon reductions.
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