Thermal bridges

Table of Contents

Home Journey - This article is part of a series.

Part 1: Introduction

Part 2: Gap sealing

Part 3: Wall insulation

Part 4: Secondary glazing

Part 5: Window coverings

Part 6: Slab edge insulation

Part 7: Box gutter insulation

Part 8: Ceiling insulation

Part 9: This Article

Part 10: Conclusions

Steel beams are the weakest link. Thermally speaking.

Structural steel
#

Here is a photo during construction showing some structural steel.

Because these elements are not covered by any insulation, they efficiently conduct heat between inside and outside. Steel is about 500 times more conductive than timber.

Inexplicably, the building code and NatHERS star ratings do not even attempt to account for this.

The most obvious structural steel elements are around the high windows and shutters on the east and west sides of the house. Here is one example, a high shutter in the Study:

and in infra-red, you can see thermal bridging in action:

There’s not much more to say. I do not know of a good way to fix this. Only one of the thermal bridges I was able to treat: a steel pole in the Family room. I was able to cover it with a foam tape.

This is not much in terms of insulation, but at least shields the cold surface.

Aluminium trim
#

Some of the walls are lined with Durra Panel (straw board) internally. These are edged all around with aluminium angles. It looks great but the aluminium acts as a thermal bridge (like an aluminium framed window), bypassing the insulating strawboard panel.