Scientists create rooftop paint that cools cities and harvests water PHOTO

Researchers in Australia have developed a nanoengineered rooftop coating that can both reduce building temperatures and harvest water from the air, targeting two pressures increasingly linked to climate change: rising urban heat and growing water scarcity in many regions.

Water stress is intensifying globally as demand rises and climate variability disrupts rainfall patterns, placing pressure on cities to secure alternative and decentralised sources of supply, US media reports.

Against this backdrop, scientists at the University of Sydney and startup Dewpoint Innovations say their technology could offer a supplementary solution.

The coating uses passive radiative cooling to reflect sunlight and emit heat back into the atmosphere. In trials, it achieved solar reflectance of up to 96%, compared with 70–80% for typical white paint, and kept roof surfaces up to 30°C cooler than standard dark roofs.

“One of the amazing properties of having a surface that is maintaining a cooler temperature, while the rest of the environment is increasing in heat, is that it also encourages any moisture in the air to condense on its surface,” Dewpoint chief executive Perzaan Mehta told CNN.

In early tests, a 200 square metre roof produced up to 74 litres of water per day under humid conditions, though performance depends heavily on relative humidity. “It’ll help reduce the burden, but it’s not the miracle cure,” Mehta said.

The company says the cooling effect could cut household air-conditioning energy use by up to 34%, while also helping to mitigate the urban heat island effect in cities. It is preparing wider trials and potential commercial rollout through Australian paint manufacturer Haymes Paint, with pricing expected to be broadly comparable to other functional coatings.