Ultra-white paint could cool buildings, reducing the need for air conditioning

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Written by Sara Spary, CNN

Scientists have developed an “ultra-white” paint that reflects light, which they say could eliminate the need for air conditioning and even reduce carbon emissions if used on a mass scale.
The paint, developed by engineers at Purdue University in Indiana as part of a six-year project, is capable of reflecting up to 98.1% of sunlight and therefore has the ability to cool buildings, according to a press release. .

Unlike traditional paint, “ultra-white” paint is made with a chemical compound called barium sulfate, which is also used in the production of cosmetics and photo paper.

Barium sulfate particles are made up of different sizes, which “scatter” the sun’s rays and can even cool the immediate surrounding surfaces.

White paint has been used for centuries in warmer climates to cool buildings, but this new formula absorbs much less sunlight and therefore heat, the researchers said.

An image of the infrared camera shows how a sample of the new ultra-white paint cools the surrounding area. The image on the left shows the paint in situ, while the image on the right uses special technology to show how the surrounding area cools. The darker the color, the lower the temperature.

An image of the infrared camera shows how a sample of the new ultra-white paint cools the surrounding area. The image on the left shows the paint in situ, while the image on the right uses special technology to show how the surrounding area cools. The darker the color, the lower the temperature. Credit: Purdue University / Joseph Peoples

While regular paint will absorb between 10 percent and 20 percent of sunlight, the new paint only takes up 1.9 percent – a small enough amount to allow a building to lose heat overall, they said..

“If you were to use this paint to cover a roof area of ​​about 1,000 square meters, we estimate that you could get a cooling power of 10 kilowatts. It is stronger than the central air conditioners used by most homes.” said lead researcher Xiulin Ruan, a professor of mechanical engineering at Purdue.

The researchers said that the new white paint is so white that it is equivalent to the blackest black, “Vantablack”, which absorbs up to 99.9% of visible light.

It is “the strongest recorded,” they said, able to keep surfaces 19 degrees Fahrenheit cooler than other night environments and 8 degrees Fahrenheit lower during the strong sun.

Lukas Schertel, a light scattering expert at Cambridge University who was not involved in the research, told CNN that the findings are potentially interesting and that paint, if used on an industrial scale, could have a positive impact on the climate by reducing energy consumption.

He said research on cooling paints has gained traction in recent years and that if applied on an industrial scale, including to generators and other heat-radiating machines, then, in theory, “it could have an overall impact on efficiency.” energy ”.

The challenge would be to encourage commercial use, he said – and to do that, paint manufacturing should be scalable and affordable.

He added that the materials used in the formula are already “widely available”, but a manufacturer should “be cost-effective”.

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