# Thermal Break: Why Aluminium Windows Sweat Without One

> A thermal break is an insulating strip — usually polyamide — bonded between the inner and outer halves of an aluminium profile, so heat cannot conduct straight through the frame. Without it, the frame is a continuous metal bridge between outside and inside.

## Why it matters on a project

Aluminium is roughly a thousand times more conductive than the polyamide strip
that breaks it. That single fact is why an unbroken aluminium frame behaves like
a heat pipe through the wall — and why, in a chilled office in a humid Indian
summer, water appears on the inside face of the frame while the glass stays
clear.

Occupants read that as a leak. It is not; it is condensation on a cold metal
surface, and it is a specification decision made months earlier.

## How it is specified in practice

| Parameter | Typical position | Why |
| --- | --- | --- |
| Break material | Polyamide 6.6, glass-fibre reinforced | Low conductivity, and strong enough to be structural |
| Break depth | Commonly 14-34mm | Deeper break, better performance and higher cost |
| Assembly | Rolled-in and knurled, factory | The composite must act as one section structurally |
| Alloy | 6063 T6 | Standard architectural extrusion alloy |
| Gasket | EPDM | Durable under UV and thermal cycling |
| Verification | System U-value from the system supplier | Frame performance is a tested property, not a claim |

## Common mistakes

- **Specifying thermally broken glass and a plain frame.** Paying for
  high-performance DGU and then bridging the assembly with bare aluminium wastes
  most of the benefit at the frame.
- **Assuming it is only for cold climates.** In India the driver is usually
  cooling load and condensation control, not heating.
- **Ignoring the break depth.** "Thermally broken" covers a wide performance
  range. A 14mm break and a 34mm break are not the same product.
- **Breaking the frame and forgetting the fixing.** Steel brackets bridging
  around the break reintroduce the path the break was meant to interrupt.
- **Mixing systems.** Profile, gasket, hardware and drainage are designed as one
  assembly. Substituting one part of it invalidates the tested performance.

## Where Hagerstone uses it

Our fenestration work runs on engineered systems rather than assembled parts. As
a strategic partner, **Winda Window Systems** supplies aluminium and uPVC window
and door systems manufactured in Ludhiana as a single engineered assembly —
profile, hardware, gasket, drainage and glass — using **6063 T6 alloy, EPDM
gaskets and EN-certified hardware.**

## Standards referenced

Fenestration U-value requirements by climate zone are set by **ECBC 2017**.
Architectural aluminium extrusion alloy and temper are covered by **IS 733**.

## Frequently asked questions

### Do I need a thermal break in a hot climate like Delhi or Jaipur?

For an air-conditioned building, yes — the physics runs both ways. A non-broken frame conducts heat inwards all summer and adds to the cooling load, and its inside face runs cold enough in a chilled office to attract condensation in humid weather. The case is strongest for conditioned commercial space and weakest for naturally ventilated buildings.

### How much does it improve the U-value?

The frame component improves substantially — a thermally broken aluminium frame typically performs several times better than the same profile without one. Whole-window U-value improves less dramatically, because glass usually dominates the area. The frame matters most on heavily subdivided fenestration where framing takes a large share of the opening.

### Can a thermal break be added to an existing profile?

No. It is created during extrusion and assembly — polyamide strips are rolled into channels in two separate profiles to make one composite section. A profile is either designed as thermally broken or it is not; there is no retrofit.

## Sources

- [ECBC 2017](https://beeindia.gov.in/) — Building envelope — fenestration U-value
- [IS 733](https://standards.bis.gov.in/website/published-standards/department-wise) — Wrought aluminium alloy bars, rods and sections

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Source: https://hagerstone.com/glossary/thermal-break-aluminium