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 [url=https://www.theguardian.com/australia-news/2025/sep/17/heatwaves-caused-more-than-1000-deaths-in-australia-over-four-year-period-study-finds]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.

In well-insulated buildings, a 6C decrease in roof temperature “might result in a smaller fraction of that cooling being reflected in the top level of the house”, Neto said, but greater temperature reductions would be expected in most Australian houses, “where insulation is quite poor”.

She said the coating could also help reduce the urban heat island effect, in which hard surfaces absorb more heat than natural surfaces, resulting in urban centres being 1C to 13C warmer than rural areas.