A simple evaluator of building envelope moisture condensation according to an European Standard

Abstract

The object of this work is the thermal and moisture performance analysis of building exterior walls, by means of a software code developed by the authors, according to the European Standard ISO 13788:2001. In particular, the European Standard focuses on two of the main reasons that cause moisture degradation in building envelopes: critical surface humidity and interstitial condensation. The approach is based on the steady-state diffusion theory and calculations are carried out on monthly basis, taking into account internal moisture production rates and outdoor climatic conditions. A user-friendly software tool (TMCE, i.e. thermal and moisture control for envelopes), developed in order to quickly and easily assess moisture and thermal behaviour of building components, is presented. The software, with graphical user interface, allows: (i) to determine the minimum thermal resistance of a building component in order to avoid critical surface humidity, and (ii) to check if interstitial condensation occurs in a multi-layer wall. In case of condensation occurrence during the winter months, the rate of condensed vapour is calculated, and the possibility that the moisture is completely removed during the warmer periods is evaluated. TMCE has been then used to analyse moisture and thermal characteristics of building components on varying input parameters such as outdoor climatic conditions and indoor moisture production; some relevant results and a case study are also presented.