This paper describes characteristics of natural ventilation in the case that wind pressure and buoyancy powers effect simultaneously. Measurements of natural ventilation were performed in the building with hybrid ventilation system, and the ventilation characteristic was clarified. The measurement results were verified by the ventilation model. This basic ventilation model is characterized by simultaneous calculation of ventilation and indoor temperature. Experiment results of the ventilation characteristics were inspected by this model. By using the static analysis of measurements and the result from the ventilation model, we examined the weather conditions suitable for natural ventilation and the number of annual available time to use natural ventilation.
