Heat loss due to linear thermal bridging

The heat loss due to linear thermal bridging (${\displaystyle H_{TB}}$) is a physical quantity used when calculating the energy performance of buildings. It appears in both United Kingdom^[1] and Irish^[2] methodologies.

Calculation

The calculation of the heat loss due to linear thermal bridging is relatively simple, given by the formula below:^[3]

${\displaystyle H_{TB}=y\sum A_{exp}}$

In the formula, ${\displaystyle y=0.08}$ if Accredited Construction details used, and ${\displaystyle y=0.15}$ otherwise, and ${\displaystyle \sum A_{exp}}$ is the sum of all the exposed areas of the building envelope,