Soladigm has licensed research from LBNL that could solve these problems. The research came from Tom Richardson, a researcher at LBNL's Advanced Energy Technologies Department who found novel alternatives to tungsten oxide. In one, a magnesium-based electrochromic layer reacts with hydrogen ions to reflect light. In another, an alloy of antimony with materials such as copper or silver is used with lithium ions to do the same. The reflective approaches not only prevent heat buildup, but also can precisely control the amount of visible and near-infrared light that the window blocks, Richardson says.

Either approach could better control the amount of heat from near infrared, making it possible to significantly warm up a room in cold days. "There might be time when you want light blocked but you want the near-infrared to get in. In the winter, you want light and the heat to warm up the house, so having the ability to switch both or independently will be ideal," Richardson says.

The ability to manage the amount of light and heat that gets into a room sets electrochromic windows apart from low-emittance, or low-E, windows. Low-E windows have a metal oxide coating that reflects near-infrared light and allows most visible light to pass through. These windows generally cost around $10 per square foot.

Some experts say that installing electrochromic windows could cost considerably more than installing low-E windows for certain types of buildings. "To do a whole façade, you would have to run electricity to each window, and that might be cost-prohibitive," says Aaron Smith, a researcher in the Lighting Research Center of Rensselaer Polytechnic Institute. "It also would be more difficult to install them when retrofitting older buildings."