What is a thermal bridge? How can thermal bridging be minimised?
Energy efficiency is becoming increasingly important in today’s building designs and the thermal performance of the insulated building envelope is a key design consideration.
A thermal bridge (or cold bridge) is a weak point in the insulation. They occur when a material with a relatively high thermal conductivity penetrates the insulation layer. Cold from the external environment, and heat from the interior, pass through the material. They result in local heat losses and reduce the thermal performance of the structure which increases heating costs and energy use.
It is often impractical to eliminate all thermal bridges on a project. It is more practical to reduce thermal bridging to an acceptable level.
The thermal transmittance of a thermal bridge can often be reduced by applying one of the following techniques:
Incorporating a thermal break into the design
Using an alternative material
Examples of this technique include:
Ancon Thermal Break used with Ancon stainless steel masonry support systems
This thermoset plastic thermal break is positioned at the interface between the masonry support and the structural frame. It offers low thermal conductivity and high compressive strength, and is proven through thermal modelling to reduce heat loss.
Ancon STS and STC Balcony Connectors
These thermally insulated balcony connectors feature thermoset plastic thermal pads at the interface with steel. These systems are proven through thermal modelling to reduce heat loss while providing structural integrity.
Below is a table summarising the thermal conductivity of various construction materials. As shown by the table, the selection of carbon steel over aluminium, and stainless steel over steel will reduce the effects of a thermal bridge (material choice however can involve a number of factors, such as cost, weight, performance etc as well as thermal conductivity).
Thermal Conductivity of Some Common Construction Materials
|Material||Approx. Thermal Conductivity (W/mK)|
Many Ancon products are manufactured from stainless steel which offers high strength, a long service life and a relatively low thermal conductivity when compared to other metals, as well as being easily formed and welded. Stainless steel is ideal for use in cavity wall applications for essential structural components such as wall ties, masonry supports and windposts.
In addition to stainless steel wall ties, Ancon also offers the TeploTie basalt-fibre wall tie. With a thermal conductivity of less than 1.0W/mK, it is the most thermally efficient wall tie on the market and is particularly suited for wide cavity construction.
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Designed to minimise thermal bridging in masonry cavity walls, the patented Ancon Thermal Windpost (TWP2) from Leviat offers up to an impressive 70% reduction in thermal transmission through the span of the windpost.