Skyscraper Sunscreen

Chicago's skyline

Do skyscrapers need. . . sunscreen?

This is Sandra Tsing Loh with the Loh Down on Science.

It’s a concrete jungle out there, and a HOT one! Cooling big city skyscrapers with AC burns LOADS of energy. Could we save money and the environment by slathering buildings with sunscreen?

Xiangyu Li and his team at Purdue University tested a new kind of paint. That’s right, paint, not actual sunscreen. This white paint is filled with calcium carbonate, AKA chalk! Li thought that painting the outside of the building could reflect sunlight and lower temperatures INSIDE.

As a test, the team painted small palm-sized styrofoam squares with the stuff and left them out in the sun. They recorded temperatures on the surface of the squares and how much sunlight they reflected.

The chalky-white paint kept the squares almost three degrees cooler than air temperatures. It reflected over ninety-five percent of sunlight! What else? It costs about the same as other white paints.

This chalky paint could help keep skyscrapers cool and reduce carbon emissions.

Sunscreen…doctor and architect recommended!

Li, X., Peoples, J., Huang, Z., Zhao, Z., Qiu, J., & Ruan, X. (2020). Full daytime sub-ambient radiative cooling in commercial-like paints with high figure of merit. Cell Reports Physical Science, 1(10), 100221.