Researchers at the University of Sydney, working with startup Dewpoint Innovations, have developed a new paint-like coating that can cool buildings and collect water from the air without using electricity.

The nano-engineered coating reflects up to 97% of sunlight. It also releases heat into the sky, allowing coated surfaces to stay cooler than the surrounding air.

The breakthrough could help reduce indoor temperatures in hot regions. It may also offer a low-energy way to collect water in areas facing water shortages.

The coating uses passive radiative cooling. This means it sends heat away from the surface and releases it into the atmosphere.

At the same time, it reflects most sunlight instead of absorbing it. As a result, the coated surface does not heat up like normal roofs, walls or outdoor materials.

Researchers found that the surface can stay up to 6°C cooler than the surrounding air under direct sunlight.

This cooling effect also creates the right conditions for water vapor in the air to condense on the surface. The process works in a similar way to dew forming on grass or car roofs in the early morning.

The research paper says the coating can collect small amounts of water from the atmosphere.

When the surface cools below the air temperature, moisture in the air turns into liquid droplets. These droplets can then be collected.

During testing, the coating collected up to 390 milliliters of water per square meter per day in favorable conditions.

The researchers also estimated that a 200-square-meter roof could collect up to 70 liters of water on good days.

However, the actual amount depends on humidity, temperature, weather and surface size.

The coating was tested for six months on the roof of the Sydney Nanoscience Hub.

The outdoor testing helped researchers check how the material performed in real weather conditions.

The study found that the coating could extend the dew collection period by several hours. This means it could collect water for longer than normal surfaces.

The results suggest that the technology may be useful for hot and dry regions where cooling and water access are major challenges.

Buildings absorb a large amount of heat during the day. This increases indoor temperatures and raises the demand for air conditioning.

In many countries, cooling already consumes a large share of electricity. This demand is expected to grow as global temperatures rise.

A coating that cools buildings without power could reduce electricity use. It could also lower pressure on energy grids during heatwaves.

The water collection feature adds another benefit. It may help provide small amounts of clean water in remote or water-stressed areas.

The technology is promising, but it is not a full replacement for regular water supply systems.

It works best when the air has enough moisture. It may collect less water in very dry conditions.

The amount of water also depends on the size of the coated surface. A small roof or wall will collect only a limited amount.

Therefore, the coating is better seen as a support technology. It can help with cooling and provide extra water, but it cannot solve water shortages on its own.

The coating has been designed like paint, which could make it easier to apply on rooftops and building surfaces.

This matters because many cooling technologies fail to scale due to high installation costs or complex systems.

If developed commercially, the coating could be used on homes, factories, warehouses, schools and public buildings.

It may be especially useful in countries with hot climates, including Pakistan, where extreme heat and water stress are becoming more serious.

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