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Thermally broken aluminium (window frame)

Thermally broken aluminium is an aluminium window frame split by a polyamide thermal break, eliminating the cold bridge. Required to deliver IGU performance in zones 6-8.

By Dan Waring. Last updated 16 May 2026. Verified 16 May 2026.

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Thermally broken aluminium is an aluminium window or door frame system in which the external and internal frame sections are mechanically connected through a polyamide insulating strip (the “thermal break”), eliminating the direct metal-to-metal pathway that a conventional aluminium frame creates between the cold outside surface and the warm inside surface. Without the thermal break, the aluminium frame conducts heat readily and forms a thermal bridge that wastes the performance of any high-spec insulated glass unit (IGU) fitted in it.

Why it matters in the NCC 2022 (and especially NCC 2025) energy efficiency context:

  • The IGU’s U-value (rate of heat transfer through the glass) is only one input to the whole-window U-value. The frame contributes ~20-30% of the assembly area and a similar share of heat loss.
  • A standard aluminium frame has a whole-window U-value typically 4.0 to 5.0 W/m²·K even with a high-performance IGU.
  • A thermally broken aluminium frame can deliver a whole-window U-value of 2.0 to 3.0 W/m²·K, matching or beating uPVC.
  • In NCC climate zones 6, 7 and 8 (cool temperate, cool, alpine), the NatHERS modelling typically requires thermally broken aluminium or uPVC to achieve 7-star thermal rating without oversizing the IGU.

Construction of a thermally broken aluminium frame:

  1. Two separate aluminium profiles: outer (faces the weather) and inner (faces the room).
  2. Polyamide insulating strip (typically 14 to 34 mm wide, glass-fibre-reinforced) bridges the two profiles, mechanically connecting them while breaking the heat path.
  3. Rubber gaskets seal between glass and frame.
  4. Hardware (latches, hinges, lock cylinder) is structurally tied through the frame.

Cost premium and lead times:

  • 20-40% more than standard aluminium frame at same size and configuration.
  • Lead times often 8-14 weeks (vs 4-6 weeks for standard aluminium) because thermally broken frames are predominantly imported or made-to-order.
  • Project budget impact: a typical Class 1a build with thermally broken frames adds $8,000-$25,000 over standard aluminium framing.

Brands seen on Australian residential:

  • Schueco (German, premium high-spec).
  • Reynaers (Belgian, premium).
  • Architectural Window Systems (AWS) ThermalHEART (Australian, mid).
  • Capral Artisan (Australian, mid).
  • AluK (European systems, increasingly common).

Performance is product-specific. “Thermally broken aluminium” alone is not specification enough; the WERS-rated whole-window U-value is the figure the energy report relies on. Specify by manufacturer’s product line and the WERS certificate.

Also known as: thermal-break aluminium frame; TB aluminium window; thermally improved aluminium; polyamide-broken aluminium.

Category: Materials.

See also

Last updated: 2026-05-16. Verified: 2026-05-16. Quarterly review for currency.

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