Elephants don’t sweat, yet they somehow survive scorching African heat with nothing but wrinkled gray skin.

Now a team of researchers has copied that trick to build a tile that cools buildings without a single fan, compressor, or moving part. The work was led by Dorit Aviv, an associate professor of architecture at the University of Pennsylvania’s Weitzman School of Design. She worked alongside materials scientist Shu Yang from Penn Engineering and Kun-Hao Yu from Syracuse University.

Sweat is one of nature’s most efficient cooling systems. As moisture evaporates from the skin, it carries heat away quietly and constantly.

Elephants never developed that ability, yet they manage heat just fine. The secret lies in their skin. “Elephants have a network of cracks in their skin that trap water. When they spray themselves, that water stays put and evaporates slowly, cooling them over time,” Aviv explained.

The idea first came to Aviv through Yang, her longtime collaborator. It stuck partly because Aviv’s research focuses on making buildings more thermodynamically efficient in a warming world. Buildings, of course, can’t sweat either. The team’s answer is a cement-based building tile engineered to capture water, hold it, and release it slowly through evaporation. The results were striking. Under infrared heating and periodic watering, the temperature beneath the tiles held steady at 89.6°F.

Cracked commercial stucco, tested under the same conditions, climbed to 107.6°F. Uncracked stucco rose even higher, reaching 125.6°F. “In the United States, we spend roughly 90 percent of our time indoors, and buildings consume about 40 percent of primary energy – nearly half of that for heating, cooling, and ventilation,” Yang said. “A passive, bio-inspired cooling façade like this could lower surface temperatures by 10°F to 20°F compared to traditional stucco.”

Unlike a standard air conditioner, which consumes energy and releases indoor heat into the surrounding air, this system cools passively. It works with the building’s outer “skin” rather than fighting against it. Using evaporation effectively sounds simple, but most building materials are poorly suited to it. Water beads up, rolls off, or drains away before it can provide meaningful cooling.

The researchers needed a way to steer each droplet for maximum effect. That search led them somewhere unexpected: cracks. “In conventional construction, cracks signal weakness, the beginning of a material’s decline,” Yang said. “But by engineering where and how they form, we made networks of tiny channels that act like capillaries capable of pulling water across the surface and holding it in place.”