Moisture level inside buildings is a key factor influencing the durability of construction, indoor air quality, living comfort, and energy consumption. Previous studies found that this level was related to the room factors including moisture loads and ventilation conditions and to the moisture ab/desorption capacity of hygroscopic material utilized in interior of the building. The phenomenon of the indoor humidity level influenced by the dynamic moisture interaction process between hygroscopic material and indoor air has been recognized as moisture buffering effect. Some materials’ buffering properties at the material level have been intensively measured. However, there has not been enough information and testing standard for evaluating material buffering performance at the room level. Meanwhile, the material buffering properties may not be directly representative of the material buffering performance at the room level because the moisture buffering effects are influenced by room factors. This thesis reports on an experimental investigation of the impact of room factors on moisture buffering performance of wood paneling utilized as inner layer of the wall assembly and on the study of the indoor humidity level influenced by room factors and moisture buffering effect of the hygroscopic material. The experimental study presents the moisture responses of wood paneling by moisture ab/desorption kinetic curves, and finds that the buffering effect caused by hygroscopic material is related to not only the buffering performance of the material but also to the characteristics of the building structure. Under the experimental test conditions, the room characteristics can cause up to 8% variation in RH levels and wood paneling can moderate these variations by up to 30%. 
The experimental results showed that to predict indoor humidity levels, the moisture interaction between the wood paneling and indoor air was not negligible, and the room factors dominated the variation of the indoor environment. To further investigate the indoor humidity level influenced by room factors that could not be studied in the experiment and to explain the influences by the mechanisms of HAM transport, a numerical model that coupled the governing equations of momentum, heat, and moisture transport in whole building simulation domain was established. This model which took into account the heat/moisture interaction between indoor air and envelope overcomes the limitations existing in currently available numerical models of coupling moisture transport in the building envelope with indoor CFD simulation and has great application potential in whole building HAM transport studies. The application of this model presented in this thesis includes the investigation of the indoor environment influenced by moisture loads and ventilation designs, the heat/moisture transport through wall system, and the potential damage caused by moisture.