Apartment balcony has been remodeled since the government permitted remodeling in January 2006.But extended balcony has great impact on building heat gain and loss. Therefore It has problems such as increase of heating and cooling energy. So $underline{t}echnical$ solutions about window solar gain in summer is an urgent matter. The Purpose of this study is to evaluate energy performance of a blind in a double-skin facade in residential buildings by using EnergyPlus program. The results show that slat angles of $90^{circ}$ is best in energy performance if we do not consider daylight. Poorly daylighted living room needs electric light and it also causes high cooling load. On the other hand, the results show that the application of blinds controlled automatically is best for energy performance when we consider daylight. Blind slat angles of $50sim60^{circ}$ have best performance when blinds are controlled in this angle throughout the day on a clear day in August. Blind slat angles of $0sim30^{circ}$ have best performance when blinds $underline{are;controlled}$ in this angle throughout the day on a cloudy day (more than 7 of total sky cover) in August.