Window systems are one of the complicated parts in buildings, supplying the daylight and the fresh air to the room and serving as the interaction between indoor and outdoor spaces. It causes the unwanted heat gain in the summer and the heat loss in the winter. Although the thermal insulation performance of the window systems was developed mainly for preventing the heat loss in the winter, it is recently becoming important to prevent the heat gain from the outdoor in the summer as well, as buildings increasingly use the cooling systems. The heat gain in the summer period is significantly due to the solar radiation, but the sufficient studies have not been done on the energy consumption characteristics affected by those effects. The thermal insulation performance was quantitatively evaluated using Therm 6.1 and Window 6.1 simulation tools, and the on-site experiment of the cooling and heating energy consumption characteristics was carried out in this study. In addition, the annual cooling and heating energy consumption is computed using the building energy simulation software ESP-r to provide the basic data for the popularization of the system.