Thermal break or not? Where it earns its cost on a UAE project

Aluminium is a superb structural material and a poor insulator. It conducts heat roughly a thousand times more readily than the air gap inside a double glazed unit. That is the whole problem a thermal break exists to solve: without one, the frame becomes a shortcut for heat straight through the wall, bypassing whatever you specified for the glass.

A thermal break is a low-conductivity barrier — usually polyamide — bonded between the outer and inner aluminium sections so they are no longer a continuous metal path. The frame becomes two half-frames working together instead of one conductor.

Where it earns its cost

On any elevation enclosing air-conditioned space, a thermal break pays for itself twice over.

The first return is cooling load. In Dubai, peak summer design conditions sit well above 40°C while the interior is held near 23°C. That is a differential of twenty degrees or more, sustained for months. Frame area on a typical curtain wall or window system runs to between 15% and 30% of the opening, so the frame is not a rounding error in the thermal calculation.

The second return is condensation, and this is the one that generates complaints. When the internal face of a non-thermal frame is chilled by conduction from outside, it can fall below the dew point of the room air. Water forms on the frame, runs down onto the sill, and within a season you have staining, corroded fixings and a defect report. This is most common in bathrooms, kitchens and any humid, heavily occupied room.

Where it does not

The specification error we see most often is not omitting thermal breaks. It is applying them uniformly to every opening on the project because it feels like the safe choice.

There is no cooling load to save across an unconditioned area. On a staircase that is open to outside air, a plant room, a car park screen, a boundary enclosure, a service corridor or back-of-house space, the frame separates outside from outside. A thermal break there buys nothing and costs real money.

On a mid-size project, moving those openings to a non-thermal system with a matching finish can release a meaningful share of the façade budget. That money is better spent on the glass — a better coating on the west elevation will do more for comfort than a thermal break on a stairwell ever will.

How to decide, opening by opening

Mark up the elevations and ask three questions of each opening:

• Is the space behind it air-conditioned? No means non-thermal, unless another factor below applies.
• Is the room humid or heavily occupied? Bathrooms, kitchens, gyms, meeting rooms — condensation risk pushes toward a thermal break even where the cooling saving is modest.
• Does the project carry an energy target? Where a consultant has set a U-value or the project is pursuing a green building rating, the calculation decides, not judgement. Work to the specification.

Two things worth knowing before you order

The frame is only part of the system. A thermally broken frame with a single glazed pane in it is largely wasted money. Frame, glazing build-up and installation detail work together, and the weakest of the three sets the real performance.

Installation can undo the specification. A thermal break interrupted by a continuous metal fixing, or a perimeter packed with a conductive shim, reintroduces the bridge you paid to remove. This is a good reason to have the same party responsible for both the material and the installation — there is no gap for the detail to fall through.

A practical summary

Specify thermal breaks where conditioned air meets outside air, and where humidity makes condensation a risk. Use non-thermal systems with a matching finish everywhere else. Keep the finish consistent so the elevation reads as one system, and put the saving into the glass.