How to Evaluate Thermal Break Aluminum Profiles: A Buyer's Checklist

A photograph of a finished window tells you almost nothing about the profile inside it. The part that decides how the window behaves in a cold climate — the thermal break — is hidden behind the frame, and it is the component most often reduced to a phrase on a brochure: "thermal break", with no material, no drawing and no measurement behind it.

This checklist is written for the buyer who has to evaluate that claim. It covers five things in the order they should be checked, what to look at for each, and what to request as evidence. It uses the cross-section drawings on our own products page as worked examples, because a checklist you cannot apply to a real drawing is not much use.

What a thermal break actually is

A thermal break is a construction, not a coating. The interior and exterior aluminum shells are separated by a low-conductivity barrier inserted along the profile length, so heat has to travel around the barrier instead of straight through the metal. Everything that matters about a thermal break follows from that sentence: what the barrier is made of, whether it runs continuously, and whether the two shells ever touch again somewhere down the profile.

The checklist at a glance

1. Alloy and wall thickness: measured, not nominal

Start with the metal itself. Two numbers do most of the work: the alloy grade and the wall thickness of the section you are actually buying. Ours are 6063-T5 aluminum, with a 1.5 mm wall on SERIES 70 and 1.8 mm on the higher series.

The trap here is that drawings often carry a nominal thickness rather than a measured one. Ask for the measured record and for the alloy it applies to — a profile measured at one point is not the same as a profile specified on paper, and a thin wall undoes the rest of the design no matter how good the barrier is. The wall sections you would measure are visible in the SERIES 70 cross-section drawing.

What to ask: the alloy grade; the measured wall thickness with the record behind it; and the section drawing for the exact series, not a generic profile illustration.

2. The barrier: material and how many breaks

The barrier strip is where the thermal performance lives, and it is structural as well as insulating — it carries the mechanical link between the interior and exterior shells. Our profiles use PA66-GF25, a glass-fibre reinforced polyamide, chosen because it holds that link while resisting the movement that comes with temperature change.

Then count the breaks. A single break interrupts the heat path once. A double break separates the shells with two independent barriers, interrupting heat transfer twice rather than once — the construction used in SERIES 100. Neither is automatically right for every project, but you should know which one you are buying, and see it on a drawing rather than take it on trust.

What to ask: the barrier material by name, and whether the series has one barrier or two.

3. Chamber design: what each chamber is for

Multi-chamber profiles look impressive in a photograph and are easy to over-read. More chambers are not automatically better; what matters is what each chamber does. A well-designed section separates three duties: structure, insulation, and drainage.

Look at the drawing and ask three questions. Are the insulation chambers closed, or interrupted by fasteners and fixings? Does water have a drainage path that is independent of the insulation chambers, so it never travels through the part of the profile meant to stay dry? And is the wall thickness maintained around the break, rather than thinning exactly where the profile has to carry load? Our SERIES 88 cross-section shows a chambered profile laid out in that way.

How to read a cross-section in 60 seconds:

1. Find the barrier strip — it should be continuous along the section you are looking at.
2. Count chambers inside and outside the barrier, and note which ones are sealed.
3. Trace the drainage path: where does water entering the glazing rebate leave the profile?
4. Check the wall thickness around the break and at the fixing points.
5. Find the glazing rebate and confirm the spacer and seal positions match the drawing.

4. Where the profile meets the glass and the seals

A profile is only as good as its interface with the glass unit. Three details decide how that interface performs: the spacer, the seals, and the sealant.

Our standard kits use silver aluminum spacer bars; our higher series use black carbon-steel warm-edge spacers, which conduct less heat at the glass edge — the point where condensation appears first in cold weather. Our windows use EPDM weather seals around frame and sash, and glazing sealant is applied inside and out, with no exposed screws on the glazing beads. Glazing build-ups run from 5+12A+5 on our entry series to 5+12A+5+12A+5 triple glazing with argon fill across most of the higher series; the cold-climate specification guide walks through how to choose between them.

What to ask: the glazing build-up string, the spacer type per series, the seal material, and whether the glazing is sealed on both faces.

What to request as evidence

Five items are enough to evaluate almost any profile specification:

1. The cross-section drawing for the exact series being quoted.
2. The measured wall thickness record, with the alloy named.
3. The barrier material, by name.
4. The glazing build-up string and the spacer and seal specification.
5. Where a performance figure is quoted, the test report behind it — including the conditions it was tested under.

We would rather send a drawing and a measurement record than a marketing line, and we treat a supplier's inability to produce the first two items as the end of the evaluation, not as a gap to be filled later. The 12-point supplier verification checklist covers the rest of the due-diligence sequence.

Red flags in a profile specification

• A nominal wall thickness with no measured record behind it.
• The words "thermal break" with no barrier material named.
• No cross-section drawing for the exact series you are buying.
• A barrier that is interrupted by metal fixings somewhere along the profile.
• Insulation chambers with no independent drainage path.
• Performance figures supplied without test conditions — a number you cannot compare is not information.

Frequently Asked Questions

What is a thermal break in an aluminum window profile?

A thermal break is a construction, not a coating: the interior and exterior aluminum shells are separated by a low-conductivity barrier inserted along the profile length, so heat has to travel around the barrier instead of straight through the metal.

What is PA66-GF25 and why does it matter?

PA66-GF25 is a polyamide reinforced with glass fibre, used as the barrier material in our thermal break profiles. It matters because the barrier is structural as well as insulating — it carries the mechanical link between the two aluminum shells, so its material and continuity decide whether the break keeps working over years of thermal movement.

What is the difference between a single and a double thermal break?

A single break interrupts the heat path once; a double break separates the shells with two independent barriers. Our SERIES 100 uses a double thermal break, which interrupts heat transfer twice rather than once.

How can I check wall thickness if I cannot measure the profile myself?

Ask for the measured record rather than the nominal figure, and ask which alloy it applies to. Our profiles are 6063-T5 aluminum with a 1.5 mm wall on SERIES 70 and 1.8 mm on the higher series, and the cross-section drawings on our products page show the wall sections you would measure.

How many chambers should a thermal break profile have?

More chambers are not automatically better; what matters is what each chamber does. A good multi-chamber profile separates structural duties from insulation and provides a drainage path that is independent of the insulation chambers, so water never travels through the part of the profile that is meant to stay dry.

What evidence should I request before accepting a profile specification?

Request the cross-section drawing for the exact series, the measured wall thickness record, the barrier material by name, and the glazing build-up string. If a supplier cannot produce the drawing and the measurement record, the specification cannot be evaluated — and that is the point at which the conversation should stop.

Next step

If you are evaluating profiles for a project, start with the drawings: all eight of our series carry a cross-section drawing and a specification table on the products page, each anchored to the series it belongs to. For how those profiles are built and inspected, see how we manufacture — or send us the section you are considering and we will walk through it with you. You can reach the export team from the contact page.