It seems that even professionals can’t agree on a definition of what “Low-E” really means, and unfortunately, this confusion has been getting a lot of homeowners into trouble lately. Low-E stands for “low emissivity,” and is used to describe windows that are able to retain or reflect heat. This does NOT mean that they’ll slow down fade in your indoor fabrics OR block UV rays.
There are two kinds of Low-E windows: pyrolytic CVD and magnetron sputtering. The first involves applying fluorinated tin oxide to the glass while it’s being manufactured, and with magenetron sputtering, deposits of silver are inserted into the glass in many layers in succession. These layers of metal (tin or silver) reflect radiant infrared energy without blocking light—specifically, they reflect heat, and whatever side of the glass that heat originates on, this Low-E glass will reflect it back in that direction. Because of this, these windows are fantastic for keeping the heat from your furnace from escaping during the winter, and for keeping the warmth of the sun’s rays outside in the summer.
Remember that if you have Low-E windows installed in your home, you ARE going to save on your heating and cooling bills, but you AREN’T going to protect your furniture. Infrared rays are different from UV rays, and it’s the latter that causes damage to fabrics. Think of it this way: when you’re outside all day and you get a sun burn, your skin is responding to the heat rays—the infrared rays—from the sun. However, when you’re in the sun you’re also absorbing those UV rays, which overtime can cause you to develop skin cancer, primarily because they have a shorter wavelength and are able to penetrate materials more deeply than infrared. UV rays are the only kind of rays that can cause your DNA to mutate. Similarly, UV rays are the ones that will, over long periods of time, change the color of the furniture in your home. A Low-E window that hasn’t been treated with something that can also reflect UV rays is powerless to stop anything besides those infrared heat waves.
If you want to do everything you can to protect your home and its fabrics from UV rays, come into Brower Tinting and Graphics to talk about getting window film installed that will reflect UV rays!