Cool pavement can make people hotter

Reflective coatings channel sunlight raising temperatures where pedestrians walk.

October 16, 2019 |

Courtesy Pixabay

Cool pavements—reflective coatings or additives applied to concrete and asphalt—could have an unfortunate byproduct.

New research conducted in Los Angeles’ San Fernando Valley examined the impact of pavements that had been mixed with a reflective additive. The finding: reflected energy from sunlight can make people walking on the pavement significantly hotter.

According to a researcher’s sensors, on a hot, dry day, a pedestrian could feel more than 7 degrees warmer on a “cool pavement,” compared to how he or she would feel on a standard blacktop. The standard dark pavement stores some of the energy and converts it into heat, while the cool pavement reflects more energy.

Studies support the notion that reflective surfaces can reduce the heat island effect by a few degrees in urban areas, but at least in the brightest times of the day, they can make people walking on them feel hotter. Since 2015, Los Angeles has covered about 50 city blocks in reflective coatings and seals, and plans to continue with this initiative.

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