2013 R&D 100 Winner
LBL Universal Smart Window (USW) CoatingRoughly 30% of the energy consumed annually in the U.S. goes toward lighting and thermal management in buildings. Windows play a prominent role: They can save energy by providing natural light in place of electric, but they can also waste energy by allowing unwanted radiative heat transfer that increases the need for artificial heating or air conditioning. A variety of window coatings are currently on the market to maximize thermal gain. But Lawrence Berkeley National Laboratory’s Universal Smart Window (USW) coating, developed in collaboration with Heliotrope Technologies Inc., is the first to enable dynamic control over heat-producing near-infrared (NIR) radiation and visible light from the sun independent of each other.

Constructed from an advance nanocrystal conducting oxide-base electrochromatic material embedded in a transition-metal-oxide matrix, the USW coating delivers responsive climate control through three modes of operation.In “bright” mode, the window is fully transparent to both visible light and NIR. In “cool” mode, the window blocks NIR to eliminate thermal gain, but is transparent to visible light to allow natural daylighting. And in “dark” mode, the window blocks both NIR and most visible light, reducing glare while keeping the building cool. A small voltage (under 5 V) controls the optical state of the device and minimal power is consumed (less than 1 W-hr/m2) during switching.

Window coating

Lawrence Berkeley National Laboratory
Heliotrope Technologies Inc.

Development Team

The Universal Smart Window Coating development team (l-r): Delia Milliron (Lawrence Berkeley National Laboratory), Raffaella Buonsanti (Lawrence Berkeley National Laboratory), Guillermo Garcia (Heliotrope Technologies Inc.), Anna Llordes (Lawrence Berkeley National Laboratory).


The Universal Smart Window (USW) Coating Development Team
Delia Milliron, Principal Developer, Lawrence Berkeley National Laboratory
Guillermo Garcia, Principal Developer, Heliotrope Technologies Inc.
Anna Llordes, Principal Developer, Lawrence Berkeley National Laboratory
Raffaella Buonsanti, Principal Developer, Lawrence Berkeley National Laboratory
Evan Runnerstrom, Lawrence Berkeley National Laboratory