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The Case of Glass Thermal Ratings

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What is the thermal rating for laminated glass compared with double glazing? Is double glazing safety glass the same as laminated glass.? Thank you.

-Dave H.

Papakura, New Zealand



Thank you for contacting the Glass Detective with your question regarding what you refer to as “glass thermal ratings”. The quick response is as follows: ¼” (6mm) laminated glass has an approximate winter nighttime U-Value of 1.02 while a 1” (25mm) insulating glass unit made with clear glass and with no coatings of any kind has an approximate winter nighttime U-Value 0f .47. Laminated glass is a safety glass product and can be used in insulating (double glazing) assemblies. Tempered glass would also qualify as a safety glass in single or double glazed assemblies. It is suggested that you contact and work with a trusted glass shop in your area for additional information and assistance in choosing the right glass product for your project.

-Glass Detective

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Lyle Hill

Lyle Hill has been in the glass and metal industry for more than 40 years. In this time he has managed glass retail, contract glazing, mirror, architectural window, window film, and automotive glass businesses throughout America. He obtained an MBA from IIT with a focus on Technology and Engineering Management. Hill is also a columnist for glass industry trade magazines and often called the “face” of the glass industry. He has also authored books including “The Broken Tomato and Other Business Parables,” which is available through Amazon. Find out more about Lyle on Linkedin.

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3 Responses

  1. I live in south FL. I want replacement impact Windows. I hate the green color of LowE glass. My big windows face north. My electric bill is only 150 per month. I’m fine if I don’t get a reduction in my electric bill by switching to clear SGP laminated glass, but one salesman told me that that switch would actually raise my electric bill by increasing my heat gain. I think he is wrong. Is he?
    Thank you,

    1. David, based on the information you have provided, a change from a green tint to a clear glass may have an impact on your heat gain situation. However, there are neutral (meaning almost clear) low-e glass products that can be incorporated into your new glass compositions that will offset most if not all of any heat gain concerns.

  2. what are the following values of a laminated 6mm glass used in windows of the vehicle:
    * u-value
    * SHGC value
    * Visible Transmittance value
    * Visible reflectance
    * solar reflectance
    * solar transmittance
    * emissivity
    * conductivity

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