Junctions and thermal bridges

Junctions and thermal bridges

In a building that meets the Passivhaus Standard the junctions and interfaces require specific attention. It is at these points in the building fabric that heat loss can occur through thermal bridges; furthermore low surface temperatures can result in surface condensation and mould growth. Unaddressed thermal bridges can increase fabric heat loss by over 30%. This chapter considers the impact that thermal bridging and reduced surface temperatures can have upon building performance.

The concept of ‘zero thermal bridging’ can only be used successfully when using external dimensions. Due to geometry it is not possible to achieve zero thermal bridging using internal dimensions. The Passivhaus Standard considers a detail to be ‘...

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There are essentially three types of thermal bridge:

• Repeating thermal bridges

• Linear thermal bridges: The Y-value (psi-value)

• Nodal thermal bridges: The X-value (chi-value)

Linear and nodal thermal bridges are...

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It is possible to calculate thermal bridges using internal and external dimensions. The use of internal dimensions tends to underestimate heat loss. The use of external dimensions tends to overestimate heat loss. The two methods should not be...

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