Aapartment houses account for more than 60% of the total of residential buildings to be built in South Korea. In particular, a high-rise apartment house with 21 floors or more has steadily increased in densely populated areas. The heating and cooling energy demand of the apartment house is greatly affected by the shape and the thermal insulation of its building envelope. In addition to its functional efficiency, the shape of building envelope in a high-rise apartment house is considered to be an important factor for the urban landscape with diverse construction methods and materials. In this study, we analyzed the heating and cooling energy demand depending on the effective heat capacity of building structure and the installation position of thermal insulation materials as the design conditions of high-rise apartment houses. This study used the ECO2 energy analysis program for the building energy efficiency grading certification system in South Korea.