Engineers at Princeton University have quantified the cooling benefits of a simple solution for beating urban heat: reflecting solar radiation back from whence it came.

By outfitting building walls and roadways in dense urban centers with retroreflective materials, which reflect most incoming light directly back to its source, the researchers found that it could be possible to reduce surface temperatures by up to 36°F, lower surrounding air temperatures by almost 5°F, and cool human skin temperatures by almost a degree Fahrenheit.

“More people die from extreme heat in the U.S. than from any other weather-related event — heat kills more than tornadoes, tsunamis, and hurricanes combined,” said corresponding author Elie Bou-Zeid, professor of civil and environmental engineering. “And with climate change being linked to more frequent and long-lasting extreme heat events, there’s an urgent need to develop and deploy technologies that can help people stay cool.”

The researchers said their work is among the first to evaluate the potential cooling benefits of the technology at a global scale, moving beyond individual case studies to offer practical insights into how best to implement retroreflective surfaces in cities around the world.