Performance assessment of a heat and moisture dynamic simulation model in IDA ICE by the comparison with WUFI Plus

Recently, in the field of preventive conservation, the use of accurate whole-building dynamic simulation models is becoming an effective approach for preventing degradation phenomena due to changes in indoor historic climate. Among microclimate parameters, the moisture plays a key role in the degradation of organic-hygroscopic artworks as well as in the durability of building components. Some simulation codes combine both heat and moisture transfer calculations, however their capability to accurately model the moisture transport is limited. The HMWall model coupled with IDA Indoor Climate and Energy (IDA ICE) software is one of those models. This study aims at comparing the performance of the HMWall model with respect to WUFI Plus, developed by Fraunhofer Institute for Building Physics (IBP). Temperature (T) and relative humidity (RH) provided by both codes in the case of a building envelope with no infiltration, windows and incoming solar radiation, are compared. This allows to assess whether both models calculate the moisture transport throughout walls in the same way. Dynamic simulations have been run over a year by using different T-RH outdoor conditions. Even if both models are based on the same heat and moisture transport equations, RH behaviour simulated by HMWall is significantly different from that by WUFI Plus. This mainly depends on the calculation of saturated vapour pressure (psat) inside the material. Then, the Common Exercise 3 has been applied to test if HMWall were capable to affect indoor RH when cladding materials with different sorption behaviour are used. The new HMWall implemented model is resulted more effective than the previous one, and in the case of simplified building, RHs modelled by both programs are highly correlated.