Berkeley Study Looks at 'Cool Wall' Performance
A recent study by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory found that in many climates in the United States, the use of “cool” exterior walls can save building owners as much or more energy than cool roofs.
“Cool walls provide energy cost savings and emission reductions across California and the southern half of the United States,” said Ronnen Levinson, a Berkeley Lab staff scientist and leader of Berkeley Lab’s Heat Island Group who co-authored the study, published in the journal Energy & Buildings.
“In these climates, cool walls can save as much or more energy than the same size cool roof.”
The report analyzed more than 100,000 building simulations and modeled several different types and ages of homes, retail stores and office buildings in cities across California and the rest of the U.S.
Levinson explains that, while walls receive less intense sunlight than roofs, they’re also less insulated.
According to Berkeley, about 40% to 60% of all buildings in the U.S. were built before 1980, when building codes generally specified much less wall insulation than today. As a result, cool-wall savings in these older buildings could be three to six times greater than those for new buildings, the study found.
“Repainting the exterior walls of pre-1980 buildings—whether homes or office buildings or stores—with cool paint offers the greatest benefit because they have the least insulation,” Levinson said.
“And that’s not difficult to do. There are many light-colored cool paints in local home supply stores.”
In warm U.S. cities such as Miami, Florida, and Albuquerque, New Mexico, researchers found that cool walls could lead to annual heating, ventilation and air conditioning energy cost savings up to 11% for stand-alone retail stores, 8.3% for single-family homes and 4.6% for medium-sized office buildings. And for single-family homes across all California climates, the study found potential energy cost savings could range from 4–27%.
The study was supported by the Electric Performance Investment Charge program of the California Energy Commission and by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy.