Low-E is created by applying multiple layers of microscopic, undetectable metallic coatings to the surface of a piece of flat, annealed glass. The metallic coating helps block out the solar energy in the summer, while accepting and retaining warm, short-wave solar rays in the winter.
In the summer, Low-E glass filters long-wave solar radiation - reducing solar heat gain in your home as a result of the sun's direct rays. In the winter, Low-E glass takes on two responsibilities: first it lets warm, short-wave rays into the home for natural warmth; then the Low-E glass helps block the warm air inside, rather than allowing it to escape through the pane, so your heating system runs less to maintain a comfortable temperature.
Low-E glass filters long-wave radiation from the sun. This reduces solar heat gain from the summer sun, helping to keep your home cooler. Additionally, in the summertime where windows are exposed to direct radiation, Low-E coated glass blocks unwanted ultraviolet radiation and reflects away the long-wave infrared radiation that can add heat to the inside of your home.
Low-E glass takes on a new responsibility in winter months. It lets warm solar rays into your home, while blocking the heat inside of your home from getting out. In cold weather, you spend your energy dollars generation long-wave radiation, as in heat from a furnace. That heat moves toward your cooler windows, but the Low-E glass acts like a mirror reflecting it back inside to help save you money!