Influence of biofilms on thermal performance of selected plasters Available to Purchase

Biofilm is a thin layer of microorganisms that attaches to a surface of building materials with a slime layer. This layer is not desirable as it is perceived as a factor that degrade an aesthetical functions of buildings. On the other hand, the hygrothermal performance of constructions or their segments might be affected as well which is a phenomenon that is often underestimated. Higher sorptivity, slower diffusion of water vapor or changes of surface properties belong among the most influencing factors. This paper aims at quantification of light reflectance of plasters before and after inhabitation by biofilms. The data obtained experimentally by means of spectrophotometry are then used as input parameters of computational modelling that predicts the heat and moisture distribution in a given wall assembly when exposed to reference weather data for Brno, Czech Republic. The computations showed, that due to the surface inhabitation, the light absorption might reach up to 268.9% when compared to the reference surface which is subsequently reflected also in the thermal performance of the assembly, the plaster in particular. Because of the darker color of the biofilms, the surface heating rate is much higher when insolated. As a consequence, depending on a period of the reference year, the surface temperature might differ by up to 6.06 °C. Such a difference represents a considerable value that might subsequently affect other properties and parameters of plasters including thermal straining, microcracks formation or durability.