Phase change materials (PCMs) can be used for building envelope thermal management and for energy conservation because of their potential to absorb and release large amounts of heat with small wall temperature variations. In this paper, the heat transfer theory of a PCM board used for building envelopes is presented, together with a mathematical model based on the moving heat-source method. It was found that the model accurately predicted the position of the solid liquid interface in time and space, comparing with the published data. Energy and mass efficiency (EME) was proposed to evaluate the energy efficiency of PCM boards in office buildings located in various climatic regions in China for cooling. The influences on EME of parameters, including melting temperature of PCM, PCM board thickness and the heat transfer coefficient of building envelope, were analyzed. The optimal melting temperatures of PCM board, which resulted in the peak EME, in office building were 24.1 degrees C in Shenyang, 25.0 degrees C in Kunming, 253 degrees C in Zhengzhou and 25.5 degrees C Changsha, respectively. The EME increased with the increasing heat transfer coefficient of building envelope. For the city of Changsha with higher outdoor air temperature, none of the PCM boards modeled contributed effectively. (C) 2016 Elsevier Ltd. All rights reserved.