What is a thermal break in an aluminium window?

Aluminium is slim, lightweight, strong and fully recyclable, which is what makes it such a perfect material for windows and doors. But on its own it is a very good conductor of heat - and that’s where thermal break technology comes in. A thermal break is an insulating barrier - typically a high-performance polymer such as reinforced polyamide, which is installed between the inner and outer faces of our aluminium frames. This interrupts the metal-to-metal path that would otherwise allow heat to flow freely through the frame, and dramatically reduces heat loss in winter and heat gain in summer - helping to ensure that aluminium windows and doors like AluK’s 58BW and 58BD systems are amongst the most efficient on the market.

It wasn’t always like that though. In the early days of  aluminium windows, they were manufactured in the UK without a thermal break – and in some tropical climates where thermal performance isn’t particularly relevant, they still are.

It was only when companies like AluK set about applying our design ingenuity to the problem that thermal breaks in aluminium frames became the norm here. In fact, AluK was one of the first to introduce a window system with a polyurethane (PU) thermal break in the sash, way back in 1994. We have continued to innovate since then of course, and our aluminium windows now feature some of the most advance thermal break technology in the industry, alongside high density foam insulation for optimum thermal performance. 

benefits of the thermal break extend beyond just the performance though. It is the thermal break in aluminium window and door frames which ensures that the inside of the frame will never be too cold and that helps to reduce the risk of condensation as well. (You can read our guide to condensation worries here.)And the quality of the thermal break is just one element in the performance and overall U-Value of a window, the frame, the glass and the spacer bar also have a big part to play. If you want to learn more about U-Values and what they mean - click here.