Heat loss due to linear thermal bridging  The heat loss due to linear thermal bridging (formula_1) is a physical quantity used when calculating the energy performance of buildings. It appears in both United Kingdom and Irish methodologies. The calculation of the heat loss due to linear thermal bridging is relatively simple, given by the formula below:  In the formula, formula_3 if Accredited Construction details used, and formula_4 otherwise, and formula_5 is the sum of all the exposed areas of the building envelope,