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Critical locations in occupied dwellings may be susceptible to mould growth, depending on the prevalent hygrothermal conditions (temperature, humidity). Besides aesthetic and hygienic concerns, harmful substances produced and emitted by mould may threaten the occupants' health. In order to prevent mould growth, a strategy is needed which allows for the transient hygrothermal conditions occurring at those locations and for the growth conditions needed by mould. The most essential factors affecting mould growth are the temperature, the relative humidity and the substrate quality.
In order to assess the risk of mould growth under transient ambient conditions, a novel biohygrothermal method has been developed which is based on comparing the measured or simulated transient ambient conditions with the growth conditions needed by the fungi usually encountered in buildings. The moisture content of the mould spores is simulated and compared with the critical water content which allows a spore to germinate. Once germination has occurred, growth curves permit to estimate the subsequent spreading of the infestation. This simple simulation method allows to assess the risk of mould growth, based on known or computed climatic conditions. These local climatic conditions (temperature and relative humidity for the location to be assessed) may have been computed with the hygrothermal simulation program WUFI, or they may have been measured in situ.
Please note that this method only aims to assess the risk of mould growth, it is not a detailed realistic simulation of the growth processes. In particular, some assumptions have been made 'on the safe side', so that mould growth will be predicted sooner than it will occur in reality.
In addition, the model is only applicable for interior surfaces; on exterior surfaces the factors considered in the model (in particular increased humidity, due to rain) would indicate an elevated mould risk, while in reality other factors not considered here often prevent mould growth (strong heating through solar radiation, disinfection through UV radiation, washing-off through rain, etc). For other locations than interior surfaces the applicability of the program must therefore be decided case-by-case.
The basics of the biohygrothermal model are discussed in:
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K. Sedlbauer: Prediction of mould fungus formation on the surface of and inside building components. (5.3 MB) Dissertation Universität Stuttgart 2001. |
and
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K. Sedlbauer, M. Krus, K. Breuer: Mould Growth Prediction with a New Biohygrothermal Method and its Application in Practice (206 kB) Materials Conference, Lodz, 2003 |
