In this study, a hybrid ventilation system was proposed to reduce indoor cooling load owing to ventilation by using heat storage and discharge effects of some heat storage materials. A pilot system of the ventilating system, comprised of heat storage material, filter, and supply and exhaust fans, was also built. To measure the energy saving performance of the system, th following quantitative indicators were used: cool storage time, cool discharge time, heat storage material efficiency and reduction fo ventilation loads. These indicators were measured based on actual data gathered from five test operations. The result showed that polycarbonate-based heat storage material has longer cool discharge time compared to cool storage time, and reduced ventilation cooling load by over 32.9%.