A building thermal bridges sensitivity analysis

Along with the entry into force of the new European Directive 2010/31/EU on the Energy Performance of Buildings (EPBD recast), each Member State has the responsibility of supporting activities for the construction of nearly zero energy buildings with a very high energy performance. In order to achieve the new EU directive targets, designers, in addition to having to use innovative building components, also have to pay more attention to the construction details which mostly affect building envelope heat losses. It is therefore necessary not only to properly design structural nodes, in order to minimize such energy losses, but also to identify accurate numerical methods in order to appreciate the benefits of a proper design. A sensitivity analysis based on an extensive study of the linear thermal transmittance value of many types of thermal bridge, based on the methodology specified in EN ISO 10211, has been carried out in this paper. After having defined the input design variables and considering a range of variation for each of them for the linear thermal transmittance evaluation, a non-linear regression models was specifically developed for each analyzed thermal bridge considering the output values of a numerical code as data set. In order to perform the sensitivity analysis a significant and representative number of cases have been created, using a sampling technique. The ANOVA-FAST method has been performed, on the basis of the obtained results, in order to assess the contribution of each input design variable to the deviation of the linear thermal transmittance for each kind of thermal bridge.