Thermal bridge correction in energy refurbishment of existing buildings: a case study.

The recent Italian decree 26.06.2015, concerning the minimum requirements of new and renewed buildings, allows a 30% derogation on limit values of mean thermal transmittance in case of insufflation with insulating materials in cavity walls of buildings object of refurbishment. The purpose of the present paper is to study the optimal correction of thermal bridges in order to verify the respect of the mandatory values on mean thermal transmittance. Thermal bridges due to pillars and beams are considered. The correction is obtained through high performance insulating material layer on the outer side of thermal bridges. A 2-D numerical model is used to determine the linear thermal transmittance of junctions. Calculations carried out by the authors show that the limit values of thermal transmittance provided by the decree are too severe to be respected, even in case of derogation.