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.
