Thermally broken
steel.
A thermal break runs the centre line of the frame and stops heat escaping through the steel — slim sightlines kept, the cold path closed.
Steel conducts heat.
So we interrupt it.
Solid steel is strong and slim, but it carries warmth straight through the frame. A thermally broken suite separates the inside face of the section from the outside with an insulating isolator cast into the centre line — so the inside of the frame stays close to room temperature while the outside takes the cold.
That break is what lets steel hold its place in cold, alpine and coastal New Zealand. You keep the fine lines steel is known for, take a thicker insulating glass unit, and still meet the warmth a modern home expects. Deeper construction depth means a thicker unit, bigger panes and stronger thermal numbers — which is why the range steps up through three suites.
Three depths.
Deeper is warmer.
M65 TB
Thermally broken. 65mm. Bigger glass.
Higher thermal performance, larger spans, cold climates
W75 TB
Maximum thermal. 75mm. Triple-glazed.
Passive house, alpine, the coldest climates
The right call south
of the Bombays.
For high-performance homes, passive-house targets, alpine sites and harsher exposures, a thermally broken suite is the steel to specify. W50 TB matches the everyday W40 sightline with a break added; M65 TB adds depth for larger glass; W75 TB takes high-efficiency triple glazing for the coldest climates we build for.
Not every opening needs a break — internal screens, heritage retrofits and mild climates are well served by single-glazed steel. The thermal range is for the building envelope that has to keep the cold out and the warmth in, without giving up the lines.
What is a thermally broken steel window?
An insulating isolator is cast into the centre line of the frame, separating the inside face of the steel from the outside. The inside of the frame stays close to room temperature while the outside takes the cold — and the slim steel sightlines are kept.
Does every opening need a thermal break?
No. Internal screens, heritage retrofits and mild climates are well served by single-glazed steel. The thermal range is for the building envelope that has to keep the cold out and the warmth in, without giving up the lines.
Which thermally broken suite should I start with?
W50 TB matches the everyday W40 sightline with a break added; M65 TB adds depth for larger glass; W75 TB takes high-efficiency triple glazing for the coldest climates we build for. Deeper construction depth means a thicker insulating unit and stronger thermal numbers.
Are thermally broken steel windows double glazed?
Yes — the thermal suites take insulating glass units, stepping up to high-efficiency triple glazing in W75 TB. We confirm the glazing make-up for your project and wind zone when you enquire.
More on the material itself in steel vs aluminium windows, or see the full FAQ.
Don’t wait. Plan ahead.
Steel joinery is complicated to make — every joint welded, ground and finished by hand. Bring us in early with your architect and the timeline takes care of itself. Specify it at the start, not the end.