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Cyrus Farivar

Friday, Sep 12, 2008 10:25 PM UTC

Paint your roof white, save the planet

New data show that reflective surfaces offset carbon dioxide.

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According to a new study by Lawrence Berkeley Laboratory scientists, there’s an astonishingly low-tech solution that may help to cool the planet and reverse global warming. Paint your roof white.

Everyone knows that white colors on T-shirts or cars are much cooler than darker ones. Black cars are the hottest on hot days because the color absorbs the heat. White, on the other hand, reflects the heat, cooling down the person, the car or, in this case, the building.

Hashem Akbari, a physicist at the Lawrence Berkeley lab, just released a study showing that the average American 1,000-square-foot white roof could offset 10 metric tons of carbon dioxide.

According to his data, roofs constitute 20 to 25 percent of urban surfaces, while pavement is about 40 percent. Therefore, if all of those surfaces were switched to a reflective material (or color) in the 100 largest urban areas in America, his calculations show, this would offset 44 metric gigatons of carbon dioxide. That’s more than all countries emit in a single year. Further, that’s worth about $1.1 trillion at current carbon trading rates.

According to LBNL’s press release:

This 44 Gt CO2 offset is more than one year’s worth of the 2025 projected world-wide emission of 37 Gt of CO2. Furthermore, assuming a plausible growth rate of 1.5% in the world’s CO2-equivalent emission rate, the 44 Gt CO2-equivalent offset potential for cool roofs and cool pavements would counteract the effect of the growth in CO2-equivalent emission rates for 11 years.

Obviously, this is a rather large undertaking, but legislation requiring white on the roofs of buildings is one easy way to make sure that these effects are felt. As the Los Angeles Times reports, flat commercial buildings in California must have white roofs — a rule that’s been around since 2005. However, a new state law says sloped roofs on residential and commercial structures when constructed new or being retrofitted must have reflective coloring. This new rule takes effect in July 2009.

Unfortunately there’s no law (yet) in California that requires reflective surfaces on city streets or sidewalks.

(Via FP Passport)

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