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, 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: the model could predict humidity distribution in the room and show the influence of building material moisture adsorption and desorption on indoor air humidity. The results showed that the integrated zonal model, even with quite coarse meshes, could provide sufficiently reliable information about indoor humidity distributions within a room. The model could be used to analyze building material moisture adsorption and desorption behaviors and provide useful information on the cooling load.