Design of the vapor diffusion characteristics of the exterior facing of the facade thermal insulation systems

Abstract

Various facade facings - systems made of thermal insulation materials with the finishing facade renders which are directly applied to the facade walls are simple for construction and are applied in the newly built structures and they are also suitable for the application in the cases of the energy revitalization of the existing buildings. The exterior walls, and especially their outer layers, are exposed to various atmospheric influences. They cause different effects in the walls, one of them being the occurrence of the water vapor condensation. In the walls with the facade thermal insulation systems, the occurrence of the water vapor condensation may be caused by the vapor diffusion characteristics of the exterior render. At certain temperatures and humidity of the external and internal air, there are several conditions for the occurrence of the water vapor condensation in the wall with the facade thermal insulation system, when the exterior render is of higher relative resistance to the water vapor diffusion. Therefore, it is useful to determine the vapor diffusion characteristics, that is, highest values of the relative resistance to the water vapor diffusion of the exterior renders which will not cause the condensation of the water vapor in the wall, or at least those that will not cause the impermissible dampening of the wall material, and will allow for the possibility of moisture drying.