on April 20th, 2021

According to the International Energy Agency (IEA), the power needed to keep air conditioners and electric fans running accounts for 20% of global electricity use. And this is only set to increase.

The rising demand for space cooling puts an enormous amount of strain on electricity systems in many countries, all while driving up emissions. As we look towards the future, engineers are beginning to look at more abstract solutions for energy efficiency.

And this now includes paint.

Xiulin Ruanholds up his lab’s sample of the whitest paint on record.

Credit: Purdue University/Jared Pike

Purdue University engineers have created the ‘whitest paint’ yet. Tests carried out on the paint showed it reflects more than 98% of sunlight. Researchers say that buildings coated with this paint may cool them off enough to reduce the need for air conditioning.

“If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts. That’s more powerful than the central air conditioners used by most houses,” Xiulin Ruan, a Purdue professor of mechanical engineering, said in a statement.

The paint surpasses the previous ultra-white paint that was previously created by the same team.

How was it made?

The paint contains a compound called barium sulfate, which is also used to make photo paper and cosmetics white.

The barium sulfate particles are all different sizes within the paint, allowing the paint to scatter more of the light spectrum from the sun.

“A high concentration of particles that are also different sizes gives the paint the broadest spectral scattering, which contributes to the highest reflectance,” said Joseph Peoples, a Purdue Ph.D. student in mechanical engineering.

The outcome is a result of six years of research building on attempts going back to the 1970s to develop radiative cooling paint as a feasible alternative to traditional air conditioners. The team tested hundreds of different materials, narrowed them down to ten, and tested about 50 different formulations for each material.

An infrared camera shows how a sample of the whitest white paint (the dark purple square in the middle) actually cools the board below ambient temperature.

Credit: Purdue University/Joseph Peoples

Helping in the fight against climate change

Currently commercially available paints only reflect about 80—90% of sunlight, therefore making them unable to cool surfaces to temperatures lower than their surroundings. This new ultra-white paint will be able to reduce energy demands by creating lower ambient temperatures.

As it uses a standard acrylic solvent, the paint could be manufactured like any other, the researchers stated. It would also be similar in price to other commercial paints, as barium sulphate is actually cheaper than titanium dioxide. 

According to the BBC, the university and the research team have filed a patent for the paint and are working towards commercialization. They believe that the paint will be widely available in the market in one or two years.

Whether this solution will prove successful on a mass scale will be something only time can tell. However, paired with other energy efficient innovations, it is indeed a step in the right direction.

Greening City Roofs

Green roof on modern buildings and other residential buildings in Sydney, Australia during sunrise

Painting city roofs with the ‘whitest paint’ is not the only roof-based energy solution that is currently around. Introducing the green roof!

This relatively new global movement has taken advantage of wasted roof spaces by covering them with vegetation and a waterproofing membrane, amongst other layers. Not only are they aesthetically pleasing but this innovative solution meets a number of other environmental demands.

From purifying the air to regulating indoor temperatures, green roofs are an integral part of future climate-proof construction. Furthermore, green spaces are scientifically proven to provide stress relief, increase social interaction, encourage physical exercise and even soothe mental illness.

Exploring energy efficient solutions

Find out more about how engineers are creating efficient, innovative solutions to reduce energy consumption in buildings at our upcoming free webinar with Dr. Ana Evangelista. Reserve your spot now!


International Energy Agency. (2018). The Future of Cooling. Paris: IEA.

Gill, V., 2021. ‘Whitest ever’ paint reflects 98% of sunlight. (online) BBC News. Available at: https://www.bbc.com/news/science-environment-56749105

Service, P., 2021. The whitest paint is here – and it’s the coolest. Literally.. [online] Purdue.edu. Available at: https://www.purdue.edu/newsroom/releases/2021/Q2/the-whitest-paint-is-here-and-its-the-coolest.-literally..html

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