Glass technology in windows is complex, difficult to understand and worth a review. Windows perform many different tasks. To fully understand their performance we need to address both the heating and cooling seasons in addition to the entire system that is a building.
Low-E glass: A common term referring to glass that has low emissivity due to a film or metallic coating on the glass or suspended between two panes of glass to restrict the passage of radiant heat.
Low-E limits solar heat from entering a home while at the same time limiting heat from escaping. While it feels good to have the heat from the sun enter our home on a frigid northern winter day, the winter sun sets early and darkness claims the majority of a 24 hour day. Without the help of Low-E, the heat from our furnaces (and cool air from conditioners in the summer) quickly escapes out non-coated dual pane windows.
A range of Low-E glass options are available from most window manufacturers with varying degrees of solar heat gain, ultraviolet light protection and visible light transmission. For more information on Low-E glass types look here.
Prior to the development of Low-E, windows were uncoated single or double pane glass. Dual pane glass with Low-E coatings significantly improves energy efficiency and has saved consumers billions of dollars in energy costs according to the National Academy of Sciences.
