Energy-efficient glass, also known as low emissivity or low-e glass, was developed in the 1980s by the manufacturers Pittsburgh Plate Glass Company (PPG), among others. In 1983, PPG introduced their ”Sungate Glass” with low emissivity qualities.
Low-e glass is coated glass that allows sunlight and energy to pass through, allowing energy from the sun to enter the room. At the same time, low-e coating reflects the interior heat back into the room; thus, solar energy is used to help heat rooms, and the radiant heat loss is reduced. Energy-efficient glass is manufactured by coating the glass with a thin, transparent film comprised of various metals.