Researchers at Stanford University in California have invented a new solution to help building occupants feel cool during hot days.

They've invented a super-thin multilayered material that works like a mirror to cool buildings while simultaneously radiating heat from inside the building. The material also reflects sunlight away from buildings, which also reduces heat.

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Engineers call their technique "photonic radiative cooling." It offloads infrared heat and reflects sunlight from buildings. The method will result in cooler buildings that will require less air conditioning in the long-run.

The new coating material can be used in areas that don't have access to electrical power. It can also decrease demand for electricity by as much as 15 percent.

"The coldness of the universe is a vast resource that we can benefit from," said study co-author Shanhui Fan, an electrical engineer at Stanford.

The new material they invented consists of seven layers and is collectively just 1.8 microns thick. This makes the material thinner than the thinnest sheet of aluminum foil.

The material consists of seven layers of silicon dioxide and hafnium oxide on top of a thin layer of silver.

Each layer varies in thickness and can deal with both invisible light like infrared radiation and visible light such as sunshine.

"This is a very novel and an extraordinarily simple idea. As a result of professor Fan's work, we can now [use photonic cooling], not only at night but counter-intuitively in the daytime as well," said Eli Yablonovitch, a professor of engineering at the University of California, Berkeley, and a pioneer of photonics who directs the Center for Energy Efficient Electronics Science.

First, researchers need to determine how to conduct heat from inside the building to the exterior. Second is the scaling, or turning the pie-sized prototype into large panels needed for buildings.

Fortunately, there are existing production facilities that can scale up the prototype into thedesired sizes.

Tagsheat, Stanford University, air conditioning, photonic radiative cooling, AC, silicon dioxide, hafnium oxide, HVAC, cool buildings, invisible light, visible light