White roofs, which energy efficiency advocates have been pushing for 20 years, are finally catching on with homeowners and business across the country, the New York Times reports. The object of a campaign by Energy Secretary Steven Chu, so-called "cool roofs," which absorb less sunlight, can cut AC costs by 20% or more. Since they cost only about 15% more than standard black, they're also one of the cheapest means of combating climate change.
A global shift to white roofs would cut CO2 emissions by 24 billion metric tons over the next 20 years, estimates Art Rosenfeld, a scientist Chu calls his hero. “That is what the whole world emitted last year,” says Rosenfeld. “So, in a sense, it’s like turning off the world for a year.” Some states have even changed their building codes to encourage cool roofs. But roofers warn of a downside: in cold enough climes, say Detroit or Minneapolis, summer savings can be more than offset by a rise in heating costs.