Smart Windows Can Boost Energy Performance

Innovations in glazing technology have transformed window performance over the past three decades. Transparent glass panes can now darken in bright sunshine by means of thermochromic or photochromic films or coatings. When the temperature of the glass increases from the sun’s infrared rays, the transparency decreases, and the glass becomes clouded or frosted. With photochromic treatments, the glass occludes because of increased light intensity.

Window self-darkening coatings were adopted from eyeglass lenses that changed their tint in sunlight. These perpetually reversible rearrangements of molecules that respond to solar radiation yield big energy savings in a building’s air-conditioning demands, sometimes by as much as 25 percent. Air-conditioning accounts for about 6 percent of all electricity generated in the U.S., with its accompanying negative climate and health impacts.