Low-E (Emissivity) glass is treated with thin, virtually invisible, transparent coatings of various layers including metal oxide and silver. During the winter, Low-E glass allows the sun’s natural light and short-wave heat energy to freely pass through while reflecting long-wave heat energy back inside, keeping your home warmer. In the summer, Low-E glass reflects long-wave heat energy to the outside keeping your home cooler and, reduces the penetration of the sun’s ultraviolet (UV) rays, minimizing the fading of carpet and draperies.