As the world’s climate heats up, buildings in tomorrow’s cities will need innovative solutions to keep cool.

Channeling streams of water on a building’s skin or spraying a water mist around a structure could be unique ways to solve this issue with minimal use of energy. A team of Princeton researchers spanning two engineering departments and architecture is exploring the cooling effect of water on architecture — from small-scale prototypes to full-size structures.

“Urban surfaces are dry and dark. They absorb a lot of heat,” said Elie Bou-Zeid, associate professor of civil and environmental engineering. In a series of studies, Bou-Zeid found that spraying water on buildings could dramatically cool the surface temperature and may combat the urban heat island effect that makes cities warmer than rural areas. Having a wall with a water-flowing feature, which Bou-Zeid calls evaporative walls, or “e-walls,” would be a good alternative to green walls and roofs, which serve much the same purpose but require soil and frequent maintenance.