A thermal break is a strip of non-conductive polyamide bonded between the inner and outer halves of an aluminium frame. It stops heat conducting straight through the metal — and it is the single innovation that turned aluminium from a cold, condensation-prone frame into an A-rated one.
Aluminium conducts heat roughly 1,000 times better than uPVC. In a solid aluminium frame, the outer face and the inner face are effectively the same piece of metal, so in winter the inside of your frame sits close to the outdoor temperature. Warm indoor air hits it and condenses immediately. That is why old aluminium windows run with water every January.
A thermal break physically separates the two halves. The frame becomes two aluminium sections mechanically locked to a polyamide bridge that barely conducts at all. The outside can be at 2°C and the inside stays close to room temperature.
Open the window and look at the cut edge of the frame at the top. A thermally broken frame shows a visible strip — usually black or grey — sandwiched between two pieces of aluminium. No strip means no thermal break.
If your frames run with condensation every winter and there is no strip, that is the whole diagnosis. No glass upgrade will solve it — the frame is the cold bridge.
Because the inner and outer sections are physically separate extrusions, they can be powder coated in different colours before assembly. Anthracite outside, white inside. That is a direct side effect of the thermal break, and it is impossible in a solid frame.
A strip of non-conductive polyamide bonded between the inner and outer aluminium sections of the frame. It stops heat conducting straight through the metal, keeps the inside face of the frame warm, and is what allows a modern aluminium window to reach a U-value of around 1.2–1.4 W/m²K.
Open the window and look at the cut edge of the frame. A thermally broken frame shows a visible black or grey strip between two pieces of aluminium. If there is no strip, the frame is solid aluminium — which is why it gets so cold and wet in winter.
No. The break is built into the extrusion at manufacture. An old solid aluminium frame cannot be retrofitted with one — replacing the frame is the only fix.
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