Beware of thermal bridges in a passive house
Thermal bridges have direct impacts on the energy performance and indoor comfort of a passive house.
They can:
- Reduce the temperature of indoor surfaces, which favors the growth of mold and moisture.
According to DIN 4108-2, there is a risk of fungal growth when the surface temperature is below 12.6°C, and risk of condensation below 9.6°C. - Increase heat loss in winter and excess solar gains in summer, compromising the thermal balance of the building.
There are two main types of thermal bridges:
- Geometric – arise when there is a change of direction in the building’s envelope, such as corners of walls or connections between walls and roofs;
- Constructive – result from continuous structural elements, such as balconies or cantilever slabs.
To minimize their impact, the Passive House Institute (PHI) recommends three essential principles:
- Continuous insulation throughout the envelope — avoid interruptions in the insulating material;
- If there is an inevitable penetration of the insulation layer, use materials with low thermal conductivity (such as light concrete, wood, or polyurethane);
- At the joints between structural elements, ensure that the insulation layers connect without discontinuities or displacements.