Impact of thermal bridges on the energy response of a building

The European building stock is mainly constituted by highly energy demanding buildings. The only way to a more sustainable and decarbonized building stock is through its massive renovation. Furthermore, in order to meet the performance objectives by the European Directives within the 2050 it is necessary to drastically increase the deep renovation rate. Hence, this study is related to the application of timber based multifunctional prefabricated facades for existing buildings retrofit reducing the heating demand by the 68%. In particular, the facade panels are fixed to the existing structure by means of steel punctual anchorages which are inevitably generating a thermal bridge in the connection area. Another relevant thermal bridge is due to the vertical and horizonal joints between facade modules. Despite the presence of these criticalities is known, usually they are not considered in the energy performance analysis at building level. This study evaluates the effects of these thermal bridges on the overall performances through finite element tridimensional models. It has been estimated that those thermal bridges have a 3% influence on building energy performances. Furthermore, special attention has been paid for the cavity around the anchoring system, evaluating the effects of adding mineral wool insulation to minimize the thermal bridge. Thanks to this, a 20% reduction for the heating demand of the simulated building has been calculated.