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What is low e Glass

Understanding low-e glass

Low-e coatings play an important role in a window’s overall performance and can have a significant impact on a home’s heating, lighting, and cooling costs. What is low e glass? How does it work? To answer these questions, explain the “e” in the word “Low-E”. The “e” stands for emissivity”. Emissivity is the ability of a material to radiate energy. When solar or light energy, usually heat from the sun or the HVAC system, is absorbed by the glass, it is either deflected by the movement of the air or re-emitted by the surface of the glass.

Low E Glass

Generally, highly reflective materials have low emissivity, while dark and matte colored materials have high emissivity. All materials, including windows, re-emit heat in the form of long-wavelength infrared radiation energy, depending on their emissivity and surface temperature. Radiant energy is one of the primary modes of heat transfer through windows. To improve the insulating properties of a window, the emissivity of at least one of the surfaces of the window glass can be reduced. Therefore, low-e glass manages to improve the insulation of a home against outside temperatures, whatever the climate.

In an effort to reduce the emissivity of glass, low-e coatings have been developed to reduce the amount of ultraviolet and infrared radiation that manages to pass through the glass, without reducing the amount of visible light.

There are two types of low-e coatings: passive and solar control.
How do homeowners know if their windows are made of low-e glass?

The low-e coating is usually applied to the surface of the window glass which is facing the interior of the insulating glass. To determine if their window is made of low-e glass, homeowners can do the following test:

  • Hold a lit match or penlight in front of the window. In the double-walled insulating glass, there will be four reflections of the flame (or two per glass wall), since there are four glass surfaces in the insulating glass.
  • If the window contains Low-E glass, one of the images will be a different color from the others.
  • If the window does not contain Low-E glass, the four reflected images will be the same color.

Let Millennium Windows and Doors provide you and your project with the best quality glass money can buy.

Phone: 918-582-5025

2501 East 15th Street
Tulsa, Oklahoma 74104