In this paper, the experiment for moisture buffering and effect of ventilation rate and volume rate of the hygrothermal materials is described. The objective of the experiment is to make clear the relationships between the moisture buffering effect and, the ventilation and volume rates of the hygrothermal materials. In the experiment, a layer of gypsum board as hygrothermal materials is placed on the interior surface of the test chamber (4.60 m 3). This chamber is located in the climate room which can control constant temperature and humidity level (20°C and 50%rh). For ventilation, a mechanical fan was installed on the chamber with inlet and outlet. Two series of experiments had been carried out. First series was an experiment of ventilation rate and three conditions (i.e. no ventilation, 1.0 1/h and 5.0 1/h) were adopted. Second series was an experiment of volume late and locations of the gypsum boards. Various sizes and locations of gypsum boards were placed on the interior walls. As a result, the moisture buffering effect would be disappeared in the case of larger ventilation rate. As volume rate increase, the moisture buffering effect is getting smaller. Its effect could be not directly proportional to the volume rate. However, these results included the effect of ventilation rate, so the influence of volume rate and locations was not clear. The next stage of this study will investigate its influence.