Damage risk assessment of building materials with moisture hysteresis

Heat and Moisture Transfer (HMT) simulations are used for the calculation of moisture related damage risks in building envelopes. HMT simulations are commonly performed accepting the hypothesis of not considering the moisture hysteresis of materials. The results of HMT simulation of a timber wall with hysteresis are presented, and compared to the results of three simplied models, showing the eects of hysteresis on the simulation results and on the assessment of the risk of decay. Moisture content is the most in uenced variable, while temperature and relative humidity are slightly aected, showing that mostly damage models based on moisture content are relevantly in uenced by hysteresis. The wood decay risk analysis is performed using the simplied 20% moisture content rule. Similar temperature values and relative humidity values are calculated as simplied models, while the moisture content annual average values have dierences up to 2.3%. The wood decay risk obtained with the simplied models could be overestimated if the simulation is performed using the desorption curve, while it could be underestimated with the adsorption curve. The best approximation is obtained with the mean sorption curve, while the desorption curve and the adsorption curve could be used to calculate the upper and lower boundary of the moisture contents respectively.