Fire-resistant glass tends to have a higher U-value (poorer insulation) than standard double or triple glazing because it’s designed to withstand high temperatures, not thermal insulation. It typically doesn’t offer the same energy efficiency as regular glazing types.

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How to Know:

Fire-resistant glass is usually rated by its ability to resist fire for a specific time period (e.g., 30 minutes, 60 minutes), but if combined with a double-glazed system, you can check the U-value of the system.