Moisture levels inside buildings are influenced by many factors, including ventilation levels, daily weather conditions, seasonal climates, and material hygroscopicity. It is complex to discern the contribution of these factors in regulating moisture levels, and to quantify the capacity of hygroscopic materials applied on internal surfaces to moderate the indoor humidity, a process referred as moisture buffering. In this study, full-scale experimentation was performed on two single room test buildings (cells) to evaluate the role of moisture buffering at large scale. A statistical model was developed to extrapolate the impact of weather on the indoor moisture balance and to investigate the influence of hygroscopic materials in the room relative humidity. This is a first step into the quantification of the moisture buffering capacity of walls in buildings.