Numerical analysis on building envelope moisture condensation: A case study using the glaser diagram method

Requalification criteria with reference to existing buildings have to contemplate every aspect related to the performance of the external envelope. As for this, great attention has been posed to the modalities to increase the thermal performance of envelopes but practically no evidence has been dedicated to the study of condensation inside building elements. Several kinds of pathology may be caused by condensation, from the appearance of molds to the deterioration of the material itself. Ideally, the risk of condensation inside building elements should be identified before construction, during the design phase. Moreover, it is worth mentioning that both the above-mentioned factors are correlated: greater thermal insulation can lead to an increase in the risk of condensation and therefore it is necessary to work with reasoned choices on materials, thicknesses and position of the insulation. In this context, the present study is aimed at the analysis of the behaviour of moisture condensation with reference to a case study of a building exterior wall. Therefore, a numerical investigation has been carried out by means of a commercial code, based on finite element method, in accordance to the European Standard UNI EN ISO 13788. The Glaser method has been here employed, based on the steady-state diffusion theory and all the calculations were performed on a monthly basis, taking into account internal moisture production rates and outdoor climatic conditions. The results, with reference to the case study, present the occurrence of condensation during the winter months and the possibility that the moisture is completely removed during the warmer periods.