According to a new study by Berkeley lab researchers Dev Millstein, Ronnen Levinson, and Pablo Rosado, alongside Meichun Cao and Zhaohui Lin of the Institute of Atmospheric Physic in Beijing, so-called "cool roofs," or roofs painted white, substantially reduce the urban heat island effect during a heat wave.


 

Prior research had shown that cool roofs could mitigate the urban heat island effect, but the new study shows just how drastically this can make a difference during a heat wave. Heat waves affect both public health and energy resources, requiring massive amounts of air conditioning and other cooling systems that can overtax the electric grid.

"The hotter it is, the more cooling you get with cool roofs--and it is a significant difference, compared to the margin of error," Millstein told ScienceDaily. "We found that the stagnant conditions of a heat wave, where the air is just sitting over the city, was one of the main factors."

The research was conducted in Guangzhou, a large city in Southern China. The researchers painted all the roofs in the city to be as reflective as an old, whitened roof.