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What to Know About Low E Windows

Why are low e glass windows such a hot topic in today's home improvement news?  These specially coated windows save energy and filter UV rays.  By minimizing your heat energy loss in winter and gain in summer, these windows will reduce the amount you need to depend on your HVAC system and keep your home comfortable year round.  By filtereing UV light, they also protect room interior decor against fading.

The term "low e" stands for low emissivity, referring to a low level of heat transfer.  The glass for low e windows is treated with ultra-thin layers of metal or metallic oxide.  This reflects out infrared light (also known as 'heat energy'), reducing heat loss by 30-50%.

When comparing low e with standard windows, the following was found:

      Standard double glazing has an emissivity rate of 76%

      Low e emissivity rate can be as low as 2%

      Standard glass transmits 81% of visible light

      Low e transmits 72% of visible light

      Standard glass provides a rate of heat loss factor of .48

      Low e provides a rate of heat loss factor of .25


The cost to install low e windows is about 10-15% higher; however, these energy-efficient windows can substantially reduce your HVAC bills.


There are 2 types of low e coatings:

      Pyrolytic low e coatings, applied to hot glass during its     manufacture, are very durable and weather resistant.  You'll see them on the outside of storm windows or inside sealed multi-pane windows.  These products are often referred to as "hard-coat low e windows."

      Sputtered low e coatings, applied to cut sheets of glass at room temperature, are more vulnerable to humidity.  They are typically used for retrofitting and inside double or triple-pane windows, know as "soft-coat low e windows."


Look for Energy Star certified windows and consider low e windows for your home!   

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