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Accelerated test procedure to assess the microbial growth resistance of exterior finishes

: Künzel, H.M.; Krus, M.; Fitz, C.; Hofbauer, W.; Scherer, C.; Breuer, K.

Freitas, V.P. de; Corvacho, Helena; Lacasse, Michael ; Departamento de Engenharia Civil, Faculdade de Engenharia da Universidade do Porto -FEUP-:
XII DBMC 2011, 12th International Conference on Durability of Building Materials and Components. Vol.1 : Conference Proceedings; 12th - 15th April 2011, Porto, Portugal
Porto: FEUP, 2011
ISBN: 978-972-752-132-6
International Conference on Durability of Building Materials and Components (DBMC) <12, 2011, Porto>
Conference Paper
Fraunhofer IBP ()

Rising incidents of microbial growth on façades show the downside of energy efficiency. In cold and moderate climates, well-insulated façade systems are more prone to elevated surface moisture than traditional walls and therefore provide better growing conditions for algae and fungi. While it is difficult to alter the exterior moisture loads, the resistance of finish systems to microbial growth may be enhanced by eliminating potential nutrients, adding biocides or optimizing the material characteristics. Since progress of microbial growth under natural conditions is too slow to keep up with industrial product development schedules, an accelerated test would be beneficial. As a result of extensive exposure tests at different locations in Germany the autumn months have been identified as major growth period. Therefore, an artifical exposure chamber has been devised that simulates the conditions representative for a typical autumn day. Special lamps reproduce the effect of sunlight and wind-driven rain is imitated by weekly spray-wetting. Finish samples are installed in the climate simulator reiterates the climate cycle including night-time surface condensation until microbial growth is detected. To provide reproducible conditions a cocktail composed of typical algae and fungi is periodically applied to the tested samples. Compared to microbial growth in real life the new test is supposed to accelerate the biological processes by a factor of three to four.