New year, new projects, and the same question arises: “What’s the U-value on that glass?”
An important one too. Especially when you’re working with fire-rated glazing and trying to hit today’s energy performance targets without compromising safety.

So, let’s get straight to it.

What is a U-value (and why should you care)?
In simple terms, a U-value measures how much heat is lost through a glazing system. Lower number = better insulation. High U-value? Your building is essentially letting heat and money escape, which is not ideal.

With tightening building regulations and energy efficiency no longer being a “nice to have,” U-values now sit alongside fire ratings, integrity, and insulation performance when specifying glass, helping projects meet Part L requirements where applicable and overall energy performance targets.

Fire-rated glass doesn’t mean poor thermal performance
There’s a persistent myth that fire glass automatically means bad insulation. That might’ve been true years ago. It’s not true now.

When specified as insulated units, modern fire-resistant glazing systems can achieve competitive U-values suitable for demanding internal environments and, where required, external applications. Laminated, insulated, fire-rated units can significantly reduce heat loss while still delivering certified fire protection.

Translation: you don’t have to choose between safety and efficiency anymore.

Design smarter, not harder
Whether you’re working on commercial façades, internal partitions, stairwells or refurb projects, U-values should be considered early – not bolted on at the last minute when building control starts asking awkward questions.

Frame choice, glass make-up, coatings, and installation all play a role. Get one of those wrong and the system simply won’t perform as intended. Because it’s the whole system – glass, frame and installation that determines real-world performance.

What Fire Glass brings to the table
At Fire Glass, we don’t just sell glass – we help you specify it properly. That means fire-rated glazing solutions with documented U-values, tested performance, and zero guesswork.

If you’re planning new projects this year, now’s the time to upgrade the conversation. Fire safety, thermal efficiency, and compliance can—and should—work together.

New year. New U-values.
Let’s do glass properly.

Speak to our team to discuss your next project.
0121 667 9089
estimating@fireglassuk.com
technical@fireglassuk.com