‘Whitest’ Paint with Cooling Powers
Engineers at Indiana’s Purdue University have developed an ultra-white paint with cooling capabilities that could help curb global warming. The formulation reflects 98.1% of sunlight and radiates infrared heat away, cooling painted surfaces to below ambient temperatures. Usage on buildings could reduce the need for air conditioning systems and their associated carbon emissions.
Dubbed the ‘whitest white’, the team believe it may be the closest equivalent to Vantablack – the blackest pigment ever produced, which absorbs up to 99.9% of visible light. This extreme whiteness accounts for its cooling performance and is achieved through high concentrates (60%) of the chemical compound barium sulphate. These reflective particles are used in varying sizes to ensure the broadest spectral scattering of sunlight, thus the highest solar reflectance.
Typically, commercial white paint gets warmer rather than cooler, thanks to its UV-light-absorbing titanium dioxide content, while many solar-reflective iterations only reflect 80-90% of sunlight, and don’t reduce surface temperatures. In tests, the ultra-white paint cooled surfaces by 4.5°C below the ambient temperature, even in strong sunlight. It also kept surfaces cooler throughout the night and worked in mid-winter.
The team are now assessing the product’s long-term durability, and hope to have it on the market within two years at a comparable price to conventional paint. If adopted at scale, such passive cooling technologies could help to combat urban heat island effects that are predicted to cause city temperatures to increase by up to 3°C by 2050.
For more reflective material innovations designed to mitigate the effects of warming, see Keeping Cities Cool in Materials for Future Cities. We also explore solutions for extreme weather conditions in the Spotlight Trend Adapting to a Changing Climate. Look out for the 2021 update, coming soon.