Viitanen, H., Hanhijarvi, A., Hukka, A., Koskela, K.
2000 Proceedings of Healthy Buildings 2000, Vol. 3 341
mould, microbial growth, modeling, water damage, moisture, humidity,
structure
Viitanen, H., Hanhijarvi, A., Hukka, A., Koskela, K., (2000), "Modeling mould growth and decay damages", Proceedings of Healthy Buildings 2000, Vol. 3 341.
Abstract:
Regression models were generated on the basis of the experimental work on mould growthand decay development. The models describe the development of mould or decay in wood inrelation to humidity, temperature and the duration of exposure under different constant orfluctuating test conditions. Also a mathematical model for simulation of growth of mouldfungi on wooden material is presented. The model consists of differential equations describingthe growth rate of the mould index in fluctuating conditions including the effect of exposuretime, temperature, relative humidity and dry periods. For mould development, the minimum(critical) ambient humidity requirement was shown to be between RH 80 and 95 % dependingon other factors like ambient temperature, exposure time, organism and surface type ofmaterials. The growth of mould fungi under fluctuated humidity conditions, when favourableand unfavourable conditions are alternating, is retarded. For decay development and decaydamages buildings, the minimum response time period required for decay development isstrongly dependent on water activity and temperature. It was found that in pine sapwood thehumidity must be above RH 94 - 96% (corresponding to wood moisture contents of 25 to28%) for several weeks to activate the mycelium of the brown rot fungus Coniophora puteanaat +20ˇăC and several months at +5ˇăC. At RH 100% and temperatures between 20 and 30ˇăC,the decay rate is accelerated.