What is a thermal break, and does it matter?
A thermal break splits an aluminum frame into separate inner and outer sections joined by a rigid polyamide strut, so heat cannot conduct straight through the wall. It matters: aluminum conducts heat around a thousand times better than the insulating glass it holds, and an unbroken frame runs cold enough to condense indoor air.
Why an aluminum frame needs one at all
An untreated aluminum frame is a bridge straight through the wall: heat leaves in winter, arrives in summer, and the inner face gets cold enough to pull water out of the room air. That last effect is the one people actually notice. Condensation on the inside of a frame is rarely a glass problem; it is usually the frame conducting.
What the break is, physically
The frame is extruded as two separate aluminum sections, inner and outer, joined by a strut of polyamide — a rigid engineering plastic that carries structural load but conducts heat poorly. Our manufacturing partner uses glass-reinforced nylon PA66. The inner face is now thermally separated from the outer face.
The consequence for the building is a lower whole-window U-factor, a warmer inner frame surface, and a materially higher condensation resistance number.
Three questions that test the claim
"Thermally broken" covers everything from a serious polyamide strut to a token strip, so the phrase on its own settles nothing.
| Ask this | Why it separates suppliers |
|---|---|
| What is the strut made of, and how deep is it? | Names the material and the geometry rather than the marketing phrase. |
| Is that U-factor whole-window or centre-of-glass? | Centre-of-glass conveniently omits the frame you are asking about. |
| What is the NFRC CPD number? | A whole-product rating in a public directory cannot be argued with. |
A supplier who can answer the first two and not the third is telling you something.
The honest comparison with vinyl
On frame conduction alone, vinyl starts ahead — it is a poorer conductor, so it does not need a break. Aluminum wins on strength, which is why it carries far larger glass areas and much slimmer sightlines, and a thermally broken aluminum frame with good glazing closes most of the gap on whole-window U-factor. If your priority is the lowest possible U-factor on a small opening and looks do not matter, vinyl is the honest answer.
Source: Thermal break construction and PA66 material: the manufacturing partner’s published configuration details.
Other questions
- How long do imported aluminum windows take to arrive in the US?
- What U-factor do I need for my climate zone?
- Tilt and turn or casement: which should I specify for a US project?
- What does NFRC certification actually tell me?
- Can imported windows meet Florida HVHZ requirements?
- What documentation should a window supplier give me?
- Can a large window opening ship as one assembly?
Still the wrong question for your project?
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