A team of engineers have created what they say is the whitest paint ever with the potential to massively reduce energy usage by reflecting heat away from buildings.

The team from Purdue University in the US say the paint reflects 98.1 per cent of sunlight and is capable of keeping surfaces more than 4.5 degrees Celsius below ambient temperatures.

“If you were to use this paint to cover a roof area of about 1,000 square feet [92.9 square metres], we estimate that you could get a cooling power of 10 kilowatts,” lead researcher and professor of mechanical engineering Xiulin Ruan said. 

“That’s more powerful than the central air conditioners used by most houses.” 

Xiulin Ruan, a Purdue University professor of mechanical engineering, holds up his lab’s sample of the whitest paint on record. (Purdue University/Jared Pike)

The paint contains large amounts of barium sulfate, the chemical compound also used to make photo paper and cosmetics white.

“We found that using barium sulfate, you can theoretically make things really, really reflective, which means that they’re really, really white,” former Purdue Ph.D. candidate, Xiangyu Li said.

Contributing to the paint’s reflectiveness, the barium sulfate particles are different sizes to achieve a broad range of spectral scattering.

The only thing stopping the team from going even whiter is that higher concentrations of barium sulfate would make the paint too flaky to stick to a surface.

An infrared camera shows how a sample of Purdue’s white paint (the dark purple square in the middle) actually cools the board below ambient temperature. (Purdue University/Joseph Peoples)

Mediterranean countries have been leveraging the reflective qualities of light coloured paint for generations, and as back as far as the 1970s researchers have been developing high performance radiative cooling paints as a feasible alternative to airconditioners.

There’s already a number of products available. Companies like Dulux and Astex offer specific heat reflect products which even in darker colours have been claimed to reflect up to 50 per cent of sunlight.

According to product specifications, Dulux’s smooth cream infraCool paint reflects up to 75.2 per cent of sunlight, compared to 65.8 per cent for the standard smooth cream colour. In the charcoal colour that drops to just 26.9 per cent for the infraCool paint and 6.8 per cent without. 

The team at Purdue have filed for a patent on their new ultra-white paint and say as well as being the most light reflective paint ever, offers reliability, ease of use and compatibility with the existing commercial paint fabrication process.

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