Moisture in buildings air-envelope interaction

The aim of this thesis was to study the mass exchange between indoor air and material. The influence of several factors on moisture transfer has been verified. Also the convective mass transfer dependency on the relative humidity condition and position of the material has been checked. Finally, a new module with the sorption hysteresis model, Humi-mur, for calculations of mass flow exchanged between indoor air and material has been developed, validated and integrated into the whole building simulation tool TRNSYS. This powerful tool was used to simulate a realistic room under real climatic conditions. The tests on mass uptake have shown that the rate of mass uptake depends not only on the material and coatings but also, some relationships between mass flux and air movement and temperature have been found. The experiment on water evaporation from a free liquid surface showed that the convective mass transfer coefficient depends on the driving potential value. It was presented that for the smaller difference in the relative humidity the transport coefficient is smaller. The measurements of the convective mass transfer coefficient from a thin hygroscopic material showed that the value of the coefficient depends not only on the difference in the driving potential but also on the level of the driving potential. For the same difference the convective transport coefficient has lower values for a lower level of relative humidity. It was also shown that the convective mass transfer coefficient has lower values for samples in a vertical position than in a horizontal position. Finally, the practical use of the Humi-mur model has been presented. The results show that moisture buffering materials can improve perceived indoor air quality and prevent microbiological growth at the surface of the building envelope. It was also pointed out that neglecting the effect of sorption hysteresis on moisture flux can lead to errors in calculations