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Thermal bridges

Be careful of thermal bridges in a passive house

Thermal bridges (see definition) can have the effect on:

  • Reducing the temperature of the interior surfaces, which can lead to mould and moisture in the building. Indeed, according to DIN 4108-2 there is a risk of mould growth in the vicinity of a thermal bridge if the surface temperature is below 12.6ºC. If the temperature is below 9.6ºC there is a risk of condensation.
  • Increasing heat losses in winter and solar gains in summer

There are two types:

  • Geometric thermal bridges that appear when there is a change of direction in the building envelope (corner of the wall, connection between the wall and the roof…)
  • Thermal construction bridges (e. g. balconies).

In order to minimize those thermal irregularities, the Passive House Institute (PHI) recommends the following three rules:

  • Continuous insulating layer. Avoid interrupting it.
  • If it is not possible to avoid the penetration of the insulating layer, the thermal conductivity of the material that penetrates the layer should be as low as possible (e. g. use porous concrete, wood or polyurethane).
  • At the connections between the building elements, the insulation layers must merge into each over without interruption.