External condensations on ETICS - influence of nearby obstacles

Abstract

External Thermal Insulation Composite Systems ETICS are, now-a-days, quite common in European buildings, used both in new constructions and refurbishment. Unfortunately, ETICS can have serious problems of microbiological growth causing the cladding defacement, which gathers the building's dwellers disapproval. Studies carried out in recent years allowed understanding the hygrothermal behaviour of ETICS. It is known that microbiological growth is due to high values of surface moisture content, which results from the combined effect of surface condensation, wind-driven rain, drying process and properties of the exterior layer. Condensation occurs mostly during the night, when the exterior surface temperature is lower than the dew point temperature, as a result of long wave radiation exchange between the surface and the atmosphere. If the drying process is not sufficiently fast, the surface moisture content remains high for longer periods and consequently increases the risk of microbiological growth. This process maybe worsens by the effect of wind driven rain and by the properties of the exterior layer. Although this existing knowledge, there is little information available about the influence of obstacles near the facade on external condensation and surface moisture content. In this paper, the results of a field test campaign, carried out by the Building Physics Laboratory LFC of Porto University, are presented. Continuous measurements of several climate and surface parameters were obtained to assess the influence of obstacles on surface condensation. The climate parameters under study were air temperature and relative humidity and atmospheric radiation. The measurements on the surface included temperature and long wave radiation, with different kind of obstacles near the facade. The results of this campaign showed that nearby obstacles influence the surface temperature during the night and, consequently, surface condensation. Different obstacles configurations have different effects, which may lead to stained patterns on the facade due differential microbiological growth rates.