The paint reflects 95.5% of sunlight and "can keep surfaces up to 18 degrees Fahrenheit cooler than their ambient surroundings," said Purdue in a statement this week. That's something commercial heat-reflecting white paints haven't been able to achieve.
"Your air conditioning kicks on mainly due to sunlight heating up the roof and walls and making the inside of your house feel warmer. This paint is basically creating free air conditioning by reflecting that sunlight and offsetting those heat gains from inside your house," said study co-author Joseph Peoples.
Developing the paint was a multi-year process involving a lot of testing of different paint formulations. The team ultimately hit on calcium carbonate (a compound found in chalk, limestone and seashells) as a main ingredient.
The engineers compared the new paint with commercial white paint by looking at samples with an infrared camera. The radiative cooling paint appears purple in the image, showing that it stays cooler in direct sunlight.
The team is looking ahead to a future where the paint could be applied to houses, roofs, cars and even roads. It could help reduce the demand for energy-hungry air conditioning in buildings.
"The paint would not only send heat away from a surface, but also away from Earth into deep space where heat travels indefinitely at the speed of light. This way, heat doesn't get trapped within the atmosphere and contribute to global warming," said Purdue.