The Case of Glass Thermal Ratings


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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The Glass Detective attempts to answer all questions accurately but cannot be held liable for any information provided or omitted.  You should always work with a licensed, insured and reputable glass shop that can assess your specific needs and local building codes and offer professional services. Never attempt to cut, install, or otherwise work with glass yourself. The Glass Detective answers questions on an informational basis only.

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