Designing Around Thermal Bridging

31 July 2020 Kelly Newlands
Back in the days of single glazing and poorly insulated walls, it was obvious where precious heat was escaping from homes. Nowadays, as buildings have become more and more insulated, it’s less obvious, and previously insignificant cracks and gaps can make a big difference to the thermal efficiency of a building. In fact, in an efficient, newly built home, thermal bridging can account for up to 30% heat loss.
Thermal Bridging Diagram

What is thermal bridging?

A thermal bridge is a point at which heat is lost from the building. It can be repeating – i.e. in the case of continuous wall ties – or non-repeating – i.e. a single point of leakage.

 

Repeating thermal bridging

Depending on the build system you’re using, repeating thermal bridging is more or less inevitable. With masonry cavity-wall construction, it’s the steel wall ties; with timber framing, it’s the joints at which the frames meet. For this reason, structural insulated panels, or SIPs, are often used for buildings intended to perform to high levels of thermal efficiency. The good news is that repeating thermal bridges are predictable, so allowances can be made for them as early as the design and planning stage. There are also ways to negate their effects, like covering repeating studs with continuous insulation.

Non-repeating thermal bridging

These are trickier because they’re unpredictable. They tend to occur around openings like window fixings, loft hatches, and doors. They have the potential to reduce the overall thermal performance of the building. In general, there are also a few things you can do if you’re designing to minimise non-repeating thermal bridging.

 

Combatting thermal bridging

The best way is a fabric-first approach – start from the design up, considering how efficient your build systems and materials are from the outset. The overall shape of the house can also impact on its rate of thermal bridging. For example, dormer windows, as quaint as they may be, introduce many junctions into a structure. The more junctions, the more opportunity there is for heat to escape. This is the reason that a Passivhaus is usually built in as simple a shape as possible. When it comes to reducing thermal bridging, simplicity of shape is key.

Kingspan Timber Solutions

Kingspan Timber Solutions

Eltisley Road

Great Gransden

Sandy

SG19 3AR

01767 676400