Passive solar energy relies on windows to let in beams of sunlight to use for heat. But what happens in the summer months when you want to keep all that solar radiation out? Awnings, shades and roof overhangs can cut down on that incoming light, but there's a much cooler solution coming that promises to cut down on HVAC costs and change the way we look at sunlight from indoors. It's called smart glass.
Smart glass, or electrochromic glass, uses a tiny burst of electricity to charge ions on a window layer and change the amount of light it reflects. While low-emittance windows that block some of the sun's radiation already exist, smart glass gives you the ability to choose how much light you want to block. Tied into smart building control systems, skyscrapers could have thousands of windows tint automatically during peak hours and return to complete transparency in the evenings. Smart glass developers expect a 25 percent reduction in HVAC costs thanks to the dynamic windows [source: Tested]. Electrochromic glass is still being perfected for commercial use, but expect to see more of the glass in the coming years as competing developers bring this smart energy-saving technology to the market.