How to Decipher Glass Jargon

July 23, 2014

Choosing the size, shape, insulation, and decorative aspects of your glass structure can be a challenge on its own, but then you get to the glazing options, and it’s like decoding a second language. There are so many different variables that come into play, and sometimes it can be difficult for an end user to keep them straight. However, Solar Innovations, Inc. has provided the following information to help potential customers better understand glass jargon.

Glass is rated based on various performance criteria, including:

Visual Light Transmittance (VLT or Tvis): The amount of visible light that passes through a glazing system. The higher the VLT, the more natural light is maintained, thus reducing the need for artificial lighting.

NOTE: VLT only refers to visual light and does not consider the UV blocking qualities of the glass.

Solar Heat Gain Coefficient (SHGC): The fraction of solar heat transfer entering a building. SHGC is expressed as a percent, and a lower number equals less solar heat gain, thus better performance.

U-Value: Measures the glass’ ability to conduct heat and indicates how well the structure will retain the heated or cooled air inside. The lower the U-Value, the greater the glass’ resistance to heat flow and the higher the insulating value.

R-Value: The measure of resistance to heat gain or loss. The higher the R-Value, the greater the glass’ resistance to heat flow and the higher the insulating value. The R-Value is the inverse of U-Value.

Fading Transmission: The amount of UV energy that will pass through the glazing; this gives the best representation of relative fading rates. A lower number will provide a greater potential for reducing the fading of interior furnishings.

If you want to make sure your structure provides you and your guests with the highest comfort level, you need to carefully choose your glazing. Identifying the proper glass performance is the first step, so before you can chose your glazing, you must first understand the language. Once you have identified the glass performance your structure requires, your selection should become “clear.”