Cooling and energy technologies are usually installed on rooftops because of their direct exposure to sunlight. And while walls don’t receive the same amount of sunlight as roofs, scientists at the Lawrence Berkeley National Laboratory’s Heat Island Group say that walls can be just as important as roofs when it comes to cooling buildings and cities.

"One of the interesting things about walls, is while a wall, per unit area, gets less sunlight than a roof because it’s not in the sun all day, the insulation in a wall is usually only about half that as much in a roof. So per unit area, the benefit to making a wall cool, is about the same as the benefit of making a roof cool."

Lead scientist Ronnen Levinson says that the group will be assessing a variety of coatings that reflect sunlight and help cool buildings in China. He explains that cool walls could be an important factor for energy efficient buildings in cities with taller buildings.

"When you have a tall building, you just have much more wall area than you have roof area. So for walls, we also want to create some guidelines for use both in the U.S. and China."