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https://www.theguardian.com/environment/2025/oct/31/scientists-invent-roof-coating-reduce-indoor-temperatures-hot-days>
"Australian scientists have developed roof coatings that can passively cool
surfaces up to 6C below ambient temperature, as well as extract water from the
atmosphere, which they say could reduce indoor temperatures during extreme heat
events.
Heatwaves are becoming more intense, more frequent and more deadly due to
human-caused global heating.
One coating made from a porous film, which can be painted on to existing roofs,
works by reflecting 96% of incoming solar radiation, rather than absorbing the
sun’s energy. It also has a high thermal emittance, meaning it effectively
dissipates heat to outer space when the sky is clear. Its properties are known
as passive radiative cooling.
“The paint, even during the day when the sun is out, can be cooler than the air
around it,” said the study’s lead author, Prof Chiara Neto of the University of
Sydney.
The coolness of the painted surface also means that vapour from the atmosphere
readily condenses on its surface – similar to dew forming overnight on a car.
“This material is able to extend the period over which dew can form by at least
a couple of hours,” Neto said. “Instead of having dew forming only … say, four
to six hours on a good night, you can extend that to eight or 10 hours.”
In a study, published in the journal
Advanced Functional Materials, the
researchers tested a prototype for six months on the roof of the Sydney
Nanoscience Hub, pairing the cool paint with a UV-resistant topcoat that
encouraged dew droplets to roll down into a receptacle.
As much as 390 millilitres per sq metre per day could be collected for about a
third of the year, the scientists found. Based on that water capture rate, an
average Australian roof – about 200 sq metres – could provide up to 70 litres
on days favourable for collecting dew, they estimate.
“It would complement existing provisions of water, whether that be the grid or
rainwater,” Neto said, suggesting the system could be used in buildings in
remote locations, or where there was little access to groundwater.
“The cooling aspect and the water go hand in hand when we talk about impact,”
she said."
Via Brad Koehn and Susan ****
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*** Xanni ***
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mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
