Berkeley Lab Showcases "Cool Pavements' to Counter Urban Heat

On a sunny summer afternoon, urban air can be 2 – 5 degrees Fahrenheit warmer than rural air nearby. Elevated air temperatures associated with the "urban heat island" effect make air conditioners work harder to keep buildings cool, straining the power grid. The effect can also degrade air quality by accelerating the formation of smog.

In the pursuit of an alternative to hot asphalt, Lawrence Berkeley Lab in California is currently showcasing "cool pavements," which are designed to reflect between 30 to 50 percent of the sun's energy.

Conventional surfaces reflect only about five percent, absorbing the rest as heat. On some days, according to Benjamin Mandel, a researcher with the Heat Island Group, the new coatings are 40 degrees Fahrenheit cooler than their traditional counterparts.

Since more than a third of most cities are covered by pavement, using cooler coatings could have a big impact on reducing air temperatures and improving air quality. Studies show that lighter surfaces, combined with more vegetation, could impede the formation of smog, and reduce energy costs from traditional heat mitigation methods like conventional fans and air conditioning.

The coatings, which are made by several private companies, come in various shades and colors, and are currently displayed in Berkeley's parking lot. Mandel says they've tested eight so far. "Our showcase is intended primarily for demonstration purposes, as we show the public and local governments some cool pavement options that are currently on the market," he said.

Mandel says it's not possible to say which of the eight is best, as they have varied uses. "Some likely perform better under vehicle traffic on city roads. Others may maintain solar reflectance better over time."

Mandel says the coatings will most likely have higher installation costs than standard pavement installations, but the costs will be offset by savings from longer-lasting pavements, and better preservation of the systems underneath.