Object of this work is the thermal and moisture performance analysis of building exterior walls, according to the European Standard draft prEN ISO 13788:1997 prepared by Technical committee CEN TC89 . In order to establish design criteria and to evaluate the thermal and moisture behavior of building components , the physical model and the calculation methods are provided. In particular, the European Standard focuses on the two main reasons that cause moisture degradation in building envelopes: surface condensation and concealed condensation. The approach is based on the steady state diffusion theory and calculations are carried out on the steady state diffusion theory and calculations are carried out on monthly basis, into account internal moisture production rates and outdoor climatic conditions.
A user friendly software tool " TMCE (Thermal and Moisture Control for Envelops)" , developed in order to quickly and easily assess moisture and thermal behavior of building components, is here presented. The software , with graphical user interface, allows: i) to determine the minimum thermal resistance of a building component in order to avoid surface condensation, and ii) to check if concealed condensation occur 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 used to carry out sensitivity analysis on moisture and thermal characteristics of building components on varying input parameters such as outdoor climatic and indoor moisture production; relevant results are herein presented.