With the economic development, the energy consumption of office buildings is growing increasingly in China. The building envelop energy-saving technology (BEEST) needs to be optimized in order to improve the energy performance of office buildings. In this paper, an office building with the representative building design was selected as the building model. The BEESTs were used to improve the energy performance of exterior walls, roof and exterior windows. By the use of energy simulation software, the energy-saving effects of different BEESTs were calculated and compared with each other in the five major climatic regions of China. Then a new method which combined energy simulation with economic analysis was proposed to evaluate the optimum EPS insulation thickness. Based on sensitivity analysis, the economic EPS insulation thickness for exterior wall and roof was obtained. Finally, the optimum combinations of the BEESTs suitable for the office buildings in different climatic regions were put forward respectively and the comprehensive energy-saving effects of the optimum combinations were also evaluated. (c) 2012 Elsevier B.V. All rights reserved.