A detailed investigation of thermal performance of an air-circulation-type temperature-control system to serve as an alternative means of saving energy and heat storage is reported. The proposed system is of the hybrid type combining a central air-conditioning system, system incorporating phase-change material (PCM), and a roof ventilation layer. The said hybrid system was tested by means of an experiment performed in an actual house located in Yufuin in the Oita prefecture in Japan. Numerical analysis was performed using Hygrabe-an unsteady heat-transfer-analysis tool-for the building envelope. Results of the said experiment were observed to accurately predict the effects of radiative cooling, exhaust cooling, cold storage and release in summer, solar heat collection, and heat storage and release in winter. The potential for improved operation of the proposed system was demonstrated via parameter sensitivity analysis, which quantified the change in each effect along with resulting correlations deduced based on changes brought about in individual factors, such as air velocity, roof length, and PCM box. The proposed study, therefore, facilitates development of design guidelines for temperature-control systems to be installed in high-performance passive homes.