Effectiveness and durability of biocides in building coatings: Biological aspects

In an interdisciplinary project at the Fraunhofer-Institute for Building Physics in Holzkirchen, Germany about 350 biocide-equipped probes together with control specimens without biocide were exposed to real climatic conditions. According to a previously developed rating scale, emerging microbiological growth on the probes was assessed. The measurements of the replicates were averaged and graphically evaluated in the course of the biological development on the surfaces. All biocide equipped coatings showed a retarded growth as expected, but characteristic differences could be shown, which could be assigned to different features of the coatings and to different combinations of biocides. Further observations could be linked to elevated tolerances of special microorganisms. Due to known efficiency gaps of different biocides it is already common use to apply adjusted combinations. The important challenge is a careful and sustainable use of biocidal substances with regard to durability, energy consumption and environmental protection.