This paper describes the energy-saving effects of the proposed system with an active ventilation function and a heat pump for heat recovery. First, the temperature of the air supplied through the porous material versus the outdoor temperature was calculated using computational fluid dynamics to set the boundary conditions for the energy simulation. Then, the cooling/heating loads of a typical residential building in Japan were calculated and comparisons were made with and without the proposed system installed. In addition, in order to evaluate the energy-saving rate under different climatic conditions, the annual air-conditioning loads in several areas (Tokyo and Sapporo in Japan, and Seoul in the northwest of South Korea) were calculated. As expected, dynamic insulation applied to window frames was effective from the point of view of its insulation efficiency. The calculated results indicate that residential buildings making use of the proposed system could achieve energy savings of 14~34%. Especially it is more effective when the outdoor temperature is low in winter. In summer, the energy saving potential depends on the performance of an installed heat pump. A comparison of different climatic conditions showed that the energy-saving rate was especially high in areas with a large annual temperature difference between the indoor and outdoor environment.