Thursday, February 19, 2009
White Roofs Cool the World
Arthur Rosenfeld, California's energy commissioner, is advocating painting the town white.
"Everybody who's ever walked on a roof knows if it's white it will only heat up maybe ten degrees above ambient temperature. If it's some nice architectural green or terracotta tiles or whatever, it can heat up to eighty degrees above room temperature. So a white roof reflects solar radiation back into space where it's transparent, where it belongs, and a dark roof traps heat and contributes to the greenhouse effect."
Rosenfeld points out that this is not a new environmental technology. Greeks painted their roofs and whole buildings white 2000 years ago, and Pharaohs whitewashed their roofs 5000 years ago.
"For 1,000 square feet which is like half the area of your house, a white roof as opposed to a dark roof cools the world enough to offset the heating effects of ten tons of carbon dioxide. That's like two and a half years of emissions from your family car... If white roofs took over the world or the urban world over a twenty year program, we would save twenty five billion tons of CO2, which is the same as turning off the whole world's emissions of CO2 for one year."
Click here for a summary on how white roofs cool the earth.
And for an interview with Commissioner Rosenfeld, click on this link for PRI's Living on Earth segment entitled Painting the Town White.