At present, building energy consumption is about one-third of the total social energy consumption in China. By using wall insulation and vacuum glass, the energy saving potential of new constructions is little. Therefore, to improve the energy saving potiential of existing buildings has become a major problem that must be solved soon in china, which usually refers to improve the thermal properties of existing building envelope. Hence, it has practical significance to evaluate the economic performance of different transformation measures. In this paper, the energy consumption of a existing building with different walls, glasses and with or without external blind shading in Xi'an was simulated by eQUEST computational software. Based on the energy consumption simulation results, the economic comparison of different measures were conducted. The results indicated that by both adding polystyrene board to outer wall and adopting insulating double glass can decrease the total building energy consumption by about 10% and the investment payback period of external blind shading measures was the shortest among all the measures.
