This Coating Can Make Streets Cooler

Dark asphalt soaks up rays from the sun, exacerbating the ­problems of a warming climate. Los Angeles is trying to mitigate that heat with CoolSeal, a sealant applied on top of set asphalt that reflects solar rays instead of absorbing them. George Ban-Weiss, a professor of civil and environmental engineering at the University of Southern California, says the coating, which is based in part on his research, should last five to seven years at a cost of $25,000 to $40,000 per mile. He says a test by city officials in L.A.’s Canoga Park neighborhood reduced street temperatures by about 10 degrees.

CoolSeal’s water base and lighter silver coloring help reflect 30 ­percent to 35 percent of light, compared with the 10 percent reflection rate of standard asphalt.