Since 2005, California building code requires white roofs for flat commercial structures. Next year, new and retrofitted residential and commercial buildings, with both flat and sloped roofs, will have to install heat-reflecting roofing, as part of an energy-efficient building code.

Results could be even better if we replaced all dark roofs with white materials. As reported in a LA Times article, it’s a triple-win situation:

“First, a cooler environment not only saves energy but improves comfort. Second, cooling a city by a few degrees dramatically reduces smog. And the third win is offsetting global warming.”

These benefits were quantified in a research report published by the Berkeley Lab Heat Island Group.

Globally, roofs account for 25% of the surface of most cities, and pavement accounts for about 35%. If all were switched to reflective material in 100 major urban areas, it would offset 44 metric gigatons of greenhouse gases. That is more than all the countries on Earth emit in a single year.

As the New Republic noted, white roofs can “cut down on the need for air-conditioning in the summer”.

The idea isn’t new. The Tree Hugger was advocating this concept three years ago, and the Pueblos Blancos in Andaluzia, Spain, already have white walls and tiled roofs for centuries, to fight the storching sun.

White Towns, Andaluzia

Pueblos Blancos, Andaluzia