As mentioned in Section 1, the research hygrothermal software (WUFI 2D) was used to calculate coupled heat and moisture transfer through composites (K€unzel,1995). It requires only properties of standard material and easy-to-determine moisture storage and liquid transport functions. The program can be used for assessing the danger of interstitial condensation or the influence of driving rain on exterior building components. It can help to analyze the effect of repair and retrofit measures or the hygrothermal performance of wall assemblies under unanticipated use or in different climate zones. In addition, WUFI was proven to be is a good tool for developing and optimizing building materials and components (Trechsel, 2001).