Biocide Tolerance in Microorganisms with Respect to Durability of Building Coatings

Present state of the art does not allow guaranteeing the exemption of unwanted biological growth on building coatings under all circumstances without the use of biocides. Currently only a limited range of active substances against façade microorganisms are available. In order to achieve an appropriate and ecological use of biocides in building coatings it is important to know about possible tolerances of the target organisms. Due to known efficiency gaps of different biocides it is already common use to apply adjusted combinations. Aerophytical microorganisms, like façade algae may be capable to follow different survival strategies to avoid or tolerate biocidal ingredients. Different features of aerophytical microorganisms and the biological effects against the target organisms of typical biocides are discussed. Based on current knowledge actual demands on the modern and responsible use of biocides in building coatings shall be shown in order to stimulate the discussion among experts. Important questions are a safe use of biocidal substances on one hand and durability and energy consumption on the other. Is it possible to keep building surfaces free from microorganisms at all?