For Australia’s water sector, innovation often begins where scarcity meets ingenuity. Now, researchers at the University of Sydney have developed a paint that can cool buildings while pulling fresh water from the air. Led by Professor Chiara Neto, the team’s breakthrough could offer a new way to address heat and water stress in cities and remote regions alike.
How paint became a water source
The discovery began with a question: could a coating mimic nature’s most efficient water harvesters? Neto’s curiosity was sparked by a beetle from the Namib Desert, which collects fog droplets on its back and channels them into its mouth. “We wanted to replicate that chemistry and topography in a synthetic coating,” she said.
Her team used a porous polymer, PVDF-HFP, to create a white, paint-like material that reflects up to 97 per cent of sunlight and radiates heat away. The surface cools below the surrounding air, creating conditions for water vapour to condense. It is a process known as atmospheric water capture, which occurs without the need for fans, filters, or electricity.
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Cooling cities while collecting dew
During a six-month trial on the roof of the Sydney Nanoscience Hub, the coating remained up to six degrees cooler than ambient air. Under optimal conditions, it harvested about 390 millilitres of water per square metre per day, while the average yield on typical dew days was around 50 millilitres.
“It’s not about replacing rainfall but supplementing it,” Neto explained. “Even in dry areas, air contains water vapour, and dew can form when surfaces cool at night.”
That potential could be significant for Australia’s arid interior. While rainfall is sporadic, night-time humidity often rises, providing the right balance for condensation. Neto’s modelling suggests the technology could produce usable dew across much of the continent for nearly a third of the year.
The chemistry of cool
The paint’s performance depends on a careful interplay between surface structure and chemistry. In nature, the Namib beetle’s back alternates between hydrophilic bumps, which attract water, and hydrophobic valleys, which repel it. This contrast helps droplets form and then roll off efficiently, and the same principle drives the polymer coating’s function.
“To harvest water, you need both,” Neto said. “If the surface is too water-loving, droplets stick. If it’s too water-hating, they won’t form at all. The trick is balancing those properties, so condensation happens quickly and the droplets release easily.”
Traditional white paints rely on titanium dioxide pigments. Neto’s team achieved high solar reflectivity through internal porosity, rather than using pigments, making the coating more durable and sustainable.
The surface was fine-tuned through a process called phase inversion, in which the polymer separates into regions of different density as solvents evaporate. This creates a network of micro- and nano-scale pores that scatter sunlight like a mirror. A smooth topcoat adds the necessary hydrophobicity, allowing condensed droplets to roll away and carry dust and soot with them.
“The coating is self-cleaning,” Neto said. “As dew condenses and runs off, it removes particles that might otherwise affect its reflectivity.”
A roof that works twice as hard
Australia’s suburbs, particularly in Western Sydney, are among the hottest in the developed world. Dark roofs absorb heat, amplifying urban heat islands and increasing the demand for air conditioning. The new coating could lower roof temperatures by as much as 30 degrees compared with traditional dark paints.
“Simulations show that if enough buildings in a suburb used cool roof paints, street-level temperatures could drop by two degrees,” Neto said. “That difference can save energy and improve liveability.”
Lower surface temperatures also reduce the load on rooftop HVAC systems, which would draw in cooler air and operate more efficiently. For buildings already equipped with rainwater tanks, the coating could offer an additional benefit: dew droplets can be channelled into the same collection systems, supplementing stored water during dry spells.
Global context, local promise
Around the world, others are turning to the atmosphere for their water needs. In Chile’s Atacama Desert, vast fog-catching nets harvest mist from Pacific air currents to supply nearby villages. While effective, these systems depend on consistent fog and require maintenance. Neto’s approach uses a passive, scalable coating that can be applied directly to buildings or infrastructure without specialised structures or energy inputs.
In Australia, where more than two million homes already collect rainwater, this innovation can be easily integrated with existing systems. “A roof that stays cool and makes its own water isn’t a fantasy anymore,” Neto said.
From lab to commercial paint
Translating the discovery into a usable product required collaboration between academia and industry. Dewpoint Innovations, a start-up founded in partnership with the University of Sydney, is now commercialising the paint. Neto worked part-time with the company to guide its development.
“It was a completely different rhythm from academic research,” she said. “In science, you can adjust your question as you go. In product development, you have strict deadlines and a single goal, so you have to make it work.”
The commercial version is water-based and can be applied using standard rollers or sprayers. It is designed to withstand long-term exposure and deliver consistent cooling and condensation performance.
Opportunities for the Australian water industry
For utilities and councils, the coating’s decentralised water generation potential could support more resilient infrastructure. Even modest yields can make a difference in remote or drought-prone regions, particularly for horticulture, wildlife management or hydrogen production, which requires nine litres of water per kilogram of hydrogen.
Some local water providers have already expressed interest in the concept. Decentralised water capture could ease strain on networks by providing small, distributed sources of clean water where pipelines are costly or impractical.
Changing habits and building codes
While the technology is ready, the challenge lies in public perception. “People still prefer black roofs,” Neto said. “It’s aesthetic, but it’s also cultural. We need to show that white roofs are not just practical but essential for comfort, energy savings and water resilience.”
She hopes government planning and building standards will one day require reflective or dew-collecting coatings for energy efficiency. “Cool roof paints can save power and improve public health,” she said. “They should be seen as essential infrastructure, not an optional upgrade.”
For now, the paint represents a rare convergence of chemistry, design and environmental purpose. “Imagine a city where every roof stays cool and makes its own water,” Neto said. “That’s what this technology offers, a simple, scalable step toward a more sustainable Australia.”