What is a Thermal Break?

A Thermal break is the opposite, and the answer to a ‘thermal bridge’. Click here to see my post on thermal bridging.

Thermal bridging occurs when a more conductive material allows an easy pathway for heat flow across a thermal barrier. A Thermal Break interrupts this pathway, and consequently prevents the heat flow from crossing.

A good example of a thermal break is the building component most commonly associated with thermal breaks – windows. An aluminium window frame consists of a continuous metal profile that extends from inside to outside. A single pane of glass in a window is also a single piece of material that extends from inside to outside. These are both thermal bridges.

A thermally broken window has an insulation compound (reinforced polyamide strip, which is a non metallic, composite, structural material) fixed between the inside and outside aluminium profiles, creating an insulated barrier within the window frame. This insulation component dramatically reduces the heat flow through the assembly. Double glazing of the window also dramatically reduces the conductive heat flow through the glass. The glass surfaces are thermally broken by the air gap between them. A thermally broken, double glazed window not only helps in the way of thermal comfort & energy efficiency, it also helps in mitigating condensation on the internal surfaces.

Thermal breaks are not limited to windows. The entire building envelope benefits from thermal breaks. As I mentioned in the post about thermal bridging, wall assemblies are thermally bridged by the framing members. A solution to this problem is to install a layer of external insulation over the framing. The external insulation provides a thermal break for the framing. It greatly increases the R-value of the wall system and allows the internal insulation to achieve its full potential. External insulation helps with internal moisture management by moving the cold condensing surface to the outside, and it also helps in working towards air tightness of the building envelope.

Illustrated below is a brick veneer structure with 25mm rigid insulation (R1.0) installed on the external side of the wall frame.

GOrate extins

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