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Mold risk classification based on comparative evaluation of two established growth models

: Viitanen, H.; Krus, M.; Ojanen, T.; Eitner, V.; Zirkelbach, D.

Fulltext (PDF; )

Energy Procedia 78 (2015), pp.1425-1430
ISSN: 1876-6102
International Building Physics Conference (IBPC) <6, 2015, Torino>
Journal Article, Conference Paper, Electronic Publication
Fraunhofer IBP ()

Although the energy codes or construction standards were considerably improved in the last decades, there are continuous reports on mold growth problems in buildings. Numerical prediction can be useful in assessing the risk of mold growth in new constructions and retrofit applications. Two well-known models exist and are widely used: the VTT model and the biohygrothermal IBP model. While the VTT model is an experimentally validated empirical model based on visual findings of mold growth, the biohygrothermal method models the growth of a mold hyphen in mm as a function of the transient ambient conditions. Since a hyphen is not visible to the naked eye it is not evident at what length the growth will become a nuisance. The VTT model uses a very clear six-step evaluation: the so-called mold index describing the intensity of growth on the surface. By comparing the results of the biohygrothermal and the VTT model it is possible to use the clear and acknowledged rating measure of the mold index also for the IBP model. For this purpose, a conversion function has been developed allowing the transformation of the calculated hyphen growth, in mm, into the mold index with a high level of correspondence. In collaboration of VTT and IBP a new postprocessor for the VTT model was developed which can be used to assess both: Results from hygrothermal numerical simulations or measured data. A classification employing a traffic light indicator helps to interpret the mold growth risk: green means no risk, red is not acceptable, while the yellow range indicates a possible risk and requires a specific evaluation.