Ventilation is one of the most important techniques for cooling. However, the influence of humid must be taken into account when is ventilated under the hot and humid climate. In this paper, we discuss the passive cooling effect by the proposed ventilation mode which take account of humidity. The proposed ventilation mode are as follows: a ventilation mode where a plenty of natural ventilation operates when being outside air temperature during the period: 18°C ≤ AT ≤ 27°C (AT: ambient temperature) throughout the year. Next, then the passive cooling effect is discussed based on the results of a series of parametric simulation studies. The cooling effect is verified in four ways: (1) hourly discomfort index fluctuation without air-conditioning, (2) hourly discomfort index fluctuation with air-conditioning, (3) monthly latent heat load with air-conditioning throughout the year, and (4) possibility of surface condensation by ventilation.The results are obtained as following:(1) Discomfort index large drop by ventilation mode in the nighttime, (2) ventilation mode reduce latent heat load. Furthermore, large thermal mass reduce latent heat load, and (3) large thermal mass reduces the fear of surface condensation.