The heat loss due to linear thermal bridging ( H T B {\displaystyle H_{TB}} ) is a physical quantity used when calculating the energy performance of buildings. It appears in both United Kingdom and Irish methodologies.
Calculation The calculation of the heat loss due to linear thermal bridging is relatively simple, given by the formula below:
H T B = y ∑ A e x p {\displaystyle H_{TB}=y\sum A_{exp}}
In the formula, y = 0.08 {\displaystyle y=0.08} if Accredited Construction details used, and y = 0.15 {\displaystyle y=0.15} otherwise, and ∑ A e x p {\displaystyle \sum A_{exp}} is the sum of all the exposed areas of the building envelope,
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