The Problem With ‘Cool Pavements’: They Make People Hot

About two months ago, Ariane Middel walked the empty streets of Sun Valley, a suburban neighborhood in Los Angeles’ San Fernando Valley. The roads there had recently been coated with an asphalt mixture called CoolSeal, which lowers air temperatures by reflecting the energy from sunlight, rather than storing it and converting it into heat.

For hours, Middel and a team of researchers dragged an elaborate heat sensor, mounted to a garden cart, down the streets and sidewalks to grab meteorological data. A climate scientist at Arizona State University in Tempe—where air temperatures soar into triple digits—Middel didn’t feel all that hot. But after crunching the data, she discovered the reflected sunlight hadn’t disappeared: She had probably absorbed it.