Indoor air humidity has been recognized as an important environmental parameter, which can greatly affect the quality of indoor environment, durability of building construction component and interior furnishings, building energy consumption and the state of occupants as well as their health. Until recently, most of existing indoor humidity evaluation models were strictly based on the mass balance between humidity generation rate and humidity dilution by air leakage, ignoring moisture absorption and desorption by interior surface. This could lead to considerable inaccuracy in the predicted humidity level.  To investigate the impact of building material moisture adsorption and desorption on indoor air humidity and predict humidity distribution in a room, a zonal model was integrated with building material moisture transfer model. This integrated zonal model was developed based on the conservation of air mass, energy and water vapor mass. The model was applied to a room with forced or natural convection airflow. (Abstract shortened by UMI.)