Cooling paint harvests water from thin air

Researchers at the University of Sydney and startup Dewpoint Innovations have developed a nanoengineered polymer paint-like coating that can passively cool buildings and capture water directly from the air — all without energy input.

The invention could help tackle global water scarcity and help cool buildings, reducing the need for energy-intensive systems.

The research team led by Professor Chiara Neto created a porous polymer coating that reflects up to 97% of sunlight and radiates heat into the air, keeping surfaces up to six degrees cooler than the surrounding air even under direct sun. This process creates ideal conditions for atmospheric water vapour to condense into droplets on the cooler surface, the way steam condenses on your bathroom mirror.

Neto, from the University of Sydney Nano Institute and School of Chemistry, said the findings could have far-reaching implications.

“This technology not only advances the science of cool roof coatings but also opens the door to sustainable, low-cost and decentralised sources of fresh water — a critical need in the face of climate change and growing water scarcity,” she said.

In the six-month-long outdoor study conducted on the roof of the Sydney Nanoscience Hub, dew could be collected over 32% of the year and so could provide a sustainable and predictable supply of water even in periods with no rain. Under optimum conditions, the coatings can harvest up to 390 mL of water per square metre each day — enough for a 12-square-metre surface to supply the daily drinking needs of one person.

The study, published in Advanced Functional Materials, shows that passive cooling and atmospheric water capture can be integrated into a paint-like material for large-scale use.

Larger collection areas mean the paint could be versatile in industry: water for animals, for horticulture of high-value plants, for use in cooling by misting, or for use in hydrogen production (about nine litres of water per kilogram of hydrogen is needed in electrolysis).

Unlike traditional white paints, the porous coatings, made of polyvinylidene fluoride-co-hexafluoropropene, or PVDF-HFP, do not rely on ultraviolet-reflective pigments such as titanium dioxide.

“Our design achieves high reflectivity through its internal porous structure, delivering durability without the environmental drawbacks of pigment-based coatings,” said Dr Ming Chiu, the study’s lead author and Chief Technology Officer of Dewpoint Innovations.

“By removing UV-absorbing materials, we overcome the traditional limit in solar reflectivity while avoiding glare through diffuse reflection. This balance between performance and visual comfort makes it easier to integrate and is more appealing for real-world applications.”

Over the six-month outdoor trial, the team recorded cooling and water collection data minute-by-minute, confirming robust performance with no degradation under harsh Australian sun. Similar technologies have been shown to quickly deteriorate.

Beyond water harvesting, these coatings could help reduce urban heat island effects, lower energy needs for air-conditioning and provide climate-resilient water sources in regions facing growing heat and water stress.

Neto, also a member of the University of Sydney Net Zero Institute, said the research also challenges the assumption that dew collection only works in humid climates.

“While humid conditions are ideal, dew can form even in arid and semi-arid regions where night-time humidity rises. It’s not about replacing rainfall but supplementing it — providing water where and when other sources become limited.”

To bring the discovery from the lab to rooftops, Dewpoint Innovations is now developing a water-based paint formulation that can be applied using ordinary rollers or sprayers.

“At Dewpoint, we’re proud to partner with the University of Sydney to bring this breakthrough in passive atmospheric water harvesting to life through advanced paint-based coatings,” said Perzaan Mehta, CEO of Dewpoint Innovations.

“It’s a scalable, energy-free solution that transforms rooftops and remote infrastructure into reliable sources of clean water, helping address an urgent challenge of our time.”

With more than two million Australian homes already collecting rainwater, Neto said dew-collecting roofs could complement existing systems.

“Imagine roofs that not only stay cooler but also make their own fresh water — that’s the promise of this technology,” she said.

Image caption: Professor Chiara Neto (left) and Dr Ming Chiu holding one of the polymer-coated tiles used in the experiment.