A paint that "sweats" cools buildings with no electricity

Cooling buildings already consumes a huge and growing share of the world's electricity, and demand is rising fastest in hot, humid countries. A study published in the journal Science in 2025 describes a paint that could help cut that load, by cooling surfaces the way human skin does, partly through evaporation.

Conventional passive cooling paints work by reflecting sunlight and emitting heat as infrared radiation that passes through the atmosphere into space, a phenomenon called radiative cooling. But those paints struggle in humid climates, where water vapor in the air traps heat near the surface. The new cementitious paint, developed by an international team spanning China, Singapore, Saudi Arabia, the UK and the US, adds a third trick: its porous calcium-silicate-hydrate structure absorbs rain and water vapor, then slowly releases it through evaporation, much like sweating. The formulation reflects 88 to 92% of sunlight, emits about 95% of heat as infrared, and can hold roughly 30% of its weight in water.

“A study published in the journal Science in 2025 describes a paint that could help cut that load, by cooling surfaces the way human skin does, partly through evaporation.”

The measured results are notable. In tests in Singapore, one of the most humid major cities in the world, the paint delivered up to ten times the cooling power of commercial cooling paints, and demonstration houses stayed more than 4.5 degrees Celsius cooler than alternatives. A year-round simulation of a typical four-story house in that climate found consistent energy savings of about 34%. Because the effect is passive, it requires no power, and the team developed colored versions so buildings need not all be white.

The honest caveats: these results come from controlled tests and simulations, and long-term durability, soiling, maintenance and performance across very different climates still need to be proven at scale, as do cost and manufacturing. Even so, a passive coating that cuts cooling energy by roughly a third, and works in humidity where earlier cooling paints faltered, is a promising tool for keeping people comfortable as the planet warms, without adding to the electricity demand that drives emissions.