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What is a thermal bridge?

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The thermal efficiency of a building is a function of the thermal performance of the planar elements (e.g. wall, roofs, windows) and the local heat losses that can occur around the planar elements and where they are penetrated by the building components that conduct heat. These areas of high local heat flow, commonly known as thermal bridges, can have a significant impact on the thermal performance of the building envelope and the building energy consumption.

As part of a thermal assessment of the building envelope, heat losses due to penetrations or similar local effects have to be calculated and where necessary minimized, so that the thermal efficiency of the building envelope is within acceptable limits.

Thermal bridges can be identified using thermal imaging cameras. The thermal bridges will appear as areas of higher temperature when viewed from the exterior of a building, typically these areas appearing as red or orange in colour. This is shown in Figure 1 where higher temperatures (i.e. thermal bridges) around the door, window and balcony slab can be seen due to higher heat transfer through the assemblies. Low outside surface temperatures show that this area is well insulated, so there is much less heat flow from inside to outside. Areas with low temperatures typically appear as blue or green in colour.

Figure 2 shows a well-insulated balcony with a low outside surface temperature (blue) resulting from minimized heat transfer through the assembly.