PHOENIX -- An Arizona State University professor is doing an ongoing study to determine which of two types of roofs will help America's cities best deal with global warming.
Professor Matei Georgescu said a "cool roof" has materials that reflect heat back into space, dropping the temperature of the so-called "heat island" in cities.
But there's a trade-off.
"For Florida, the Eastern Seaboard, and the Southwest, including Arizona, the deployment of cool roofs does lead to a significant decrease in precipitation," he said.
The alternative is a "green roof," which uses vegetation to keep buildings cool. Georgescu said that type of roof doesn't have any impact on rain amounts, but he has found that it actually keeps temperatures warmer.
Georgescu claims that cool roofs could be the best choice for California, because the state doesn't get much rain during the summer. He added that further study is needed to determine which roof is better in Arizona and other states.