A thermal bridge describes a situation in a building where there is a direct connection between the inside and outside through one or more elements that are more thermally conductive than the rest of the building envelope.

Put simply, thermal bridging occurs when you have a relatively small area of your heat loss envelope (the surfaces of your home that are exposed to the cold) that has a much lower insulation value than that which surrounds it.



Imagine if you had external wall insulation on the outside of your property, which would provide an adequate level of comfort in the inside of the property. Now imagine putting a steel nail through all that insulation so it hits the brick underneath. This is a simplified example of a thermal bridge –suddenly heat loss will occur through the steel nail into the external environment, and this would also create cold spots inside the property.

Thermal bridging can lead to several problems in the property: there will be wasteful heat transfer across this element and its internal surface temperature will be different from other, better insulated internal surfaces. Warm damp air leaking through the building structure can lead to condensation within the fabric, which can reduce insulation performance and cause fabric deterioration. This can seriously affect the quality of the air for the occupants and mould spores can have a detrimental effect on human respiratory system. Therefore, thermal bridging can lead to condensation and possibly mould growth. So it’s very important to ensure there is as little thermal bridging as possible.

In modern buildings, thermal bridging can occur because of poor design, or poor workmanship. This is common where elements of the building penetrate through its insulated fabric, for example around glazing, or where the structure penetrates the building envelope, such as at balconies.

To deal with the problem, the obvious thing is to apply similar insulation to that used elsewhere in the property. However, the nature of the problem often prohibits this – for example where it occurs on a window reveal with limited space. You can try applying even a thin amount of insulation if possible. Alternatively, you can try employing additional, humidity controlled ventilation or reducing moisture vapour by installing low flow showerheads.

Reducing and limiting thermal bridging in buildings will typically reduce energy needs for the building, which means smaller energy bills! It will also ensure the occupants of the building will stay healthier and thus, happier on the long run.

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