Teresa Madaleno

Today, a lot of people are familiar with green roofs, which can help reduce energy consumption for heating and cooling, help with storm water retention, and act as a filtration system for pollutants. Now, a study suggests that the walls of a building can also be adapted to help reduce energy costs.

Campus News Centre reports indicate that scientists from the U.S Department of Energy’s Berkley Laboratory studied several different types of buildings across the United States, including home, retail and office buildings and discovered that cool exterior walls were more sunlight reflective. That’s right, a move as simple as painting walls a lighter, more reflective paint has the potential to cut energy costs and pollution.

According to the researchers, cool walls usually reflect a higher amount of incoming sunlight than average exterior walls and high thermal emittance. This means that they can efficiently release the absorbed heat. In fact, Berkeley scientist, Ronnen Levinson has been quoted saying, “…Cool walls can save as much or more energy than the same size of a cool roof.”

While walls do get less intense sunlight than roofs, they are also less insulated. Levinson also heads up Berkley’s Heat Island Group, a team that studies the rise in outdoor urban air temperature created by buildings, roads and other structures that absorb heat. He developed an interest in cool walls 10 years ago when working in China. What he realized was that there is a lot more wall area than roof area in China so he started to wonder if we should try cooling walls and not just roofs.

In the U.S somewhere between 40 and 60 percent of buildings were constructed before building codes called for higher amounts of wall insulation. The Berkley study found that cool wall savings in older buildings could be as much as six times greater than new buildings.

There is no formal definition of cool walls but the researchers are suggesting that lower performing cools walls should reflect at least 40 percent of solar energy and higher performing cools walls should reflect 60 percent. The assumption during the study was that the average wall that is not cool reflects about 25 percent sunlight.

An organization called, The Cool Roof Rating Council was established in 1998. They began as a resource people could use to learn about ratings for cool roofing products. Today the Council serves as an educational organization focused on increasing energy efficiency in buildings. The Cool Roof Rating Council is now trying to expand into ratings for cool walls.

The Berkley cool walls research was published in the journal, Energy and Buildings.