Stanford engineers have invented a revolutionary coating material that can help cool buildings, even on sunny days, by radiating heat away from the buildings and sending it directly into space.

The photonic radiative cooling method offloads infrared heat from within a building while also reflecting the sunlight that would otherwise warm it up. The result is cooler buildings that require less air conditioning.

As much as 15 percent of the energy used in buildings in the United States is spent powering air conditioning systems. The researchers say they designed the material to be cost-effective for large-scale deployment on building rooftops. Though it is still a young technology, the team believes it could one day reduce demand for electricity.

The multilayered coating, just 1.8 microns thick, also acts as a highly efficient mirror, preventing 97 percent of sunlight from striking the building and heating it up.

A warming world needs cooling technologies that do not require power, according to research associate Aaswath Raman. "Across the developing world, photonic radiative cooling makes off-grid cooling a possibility in rural regions, in addition to meeting skyrocketing demand for air conditioning in urban areas," he said.