Q&A / 

Low-E Glass

HI TIM! My husband and I built a home about two years ago and requested Low-E glass for all of the windows in our house. We mainly were trying to protect our hardwood floors and our furniture from fading. It hasn't helped, AT ALL. My curtains, dining chairs, living chairs, etc. have all faded considerably. I have reason to believe that my windows may not actually be Low-E (which we paid for) and wondered if there is any way to distinguish. Sincerely, Michele Sells

DEAR MICHELE: Low-E glass is not supposed to block ultraviolet (UV) rays of the sun which are responsible for your color-fade problems. Low-E glass does a fantastic job of blocking heat using a thin metallic coating on the inside surface of insulated-glass panels. To protect the possessions inside your home, you should have covered the windows with a window film that does stop UV radiation.

Window films are plastic sheets of varying thickness that perform many functions. Some window films stop UV rays, some stop infrared (IR) rays which cause things to heat up inside your home on a summer day. If you have ever walked in front of a window where the sun is streaming in, you can instantly feel the IR radiation on your skin. Other window films do double or triple duty. Some thicker window films will block UV, IR and large objects from coming into your home. These thicker window films are used to stop windows from being blown out during hurricanes or other large windstorms.

You can often see the ultra-thin metallic coating of Low-E if you look at clean windows on a sunny day at an approximate 30 degree angle. The glass will often appear to have a bluish or even light green cast to it. Regular glass that has no Low-E coating never has this coloration.

You may have to look at your windows at different times of the day to detect this coloration. It is not readily apparent. It may pay to go to a hardware store to buy a piece of regular glass to help you determine if you have Low-E glass. If you have someone hold the regular glass next to your windows and ensure the glass is parallel and in the same plane as the window glass, you might see that the regular glass looks very different than your windows.

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2 Responses to Low-E Glass

  1. I found a misleading statement in the article when looking up info on low-e glass.

    Unfortunately, the assertion is incorrect that low-e glass "will often appear to have a bluish or even light green cast to it. Regular glass that has no Low-E coating never has this coloration."

    This line is misleading. All common, standard plate glass with a sodal-lime composition has a green or blue-green color, which is easily seen from the side. Only optical quality glass or crystal is made without this inherent coloration.

    The addition of other chemicals, vapor depositions, or films will add to the colors and change the apparent colors of soda-lime glass.

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