Effectiveness and durability of biocidal ingredients in facade coatings.

Effectiveness and durability of biocidal ingredients in facade coatings. The use of external thermal insulation systems (ETICs) is a powerful instrument in the energetic improvement of residential buildings. With that measure, the facade surface is thermally decoupled from the wall construction and consequently the humidity balance on the facade changes. This fact leads to better conditions for the growth of microorganisms. Therefore biocidal ingredients are often added to facade coatings. To evaluate the effectiveness and the durability of biocidal equipped facade coatings a comprehensive research project was conducted at the Holzkirchen branch of the Fraunhofer-Institute for Building Physics. 33 different types of facade coatings were applied to test specimen and exposed to real weathering conditions for five years. The general efficiency of the biocidal equipping of facade coatings could be proven. The development of biological growth on biocidal equipped facade coatings was significantly reduced, showing much less species than without biocide. Depending on the type of the coating, different biocides show a varying durability within the coatings. This has an influence on the species involved in the primary colonization. The biocide content in the coating itself allows no prediction of the susceptibility to biological growth. Facade coatings with biocidal paints showed better results than biocidal renders without additional paint coating.