Ground source heat pump system takes advantage of the stable ground temperature to achieve energy savings and to reduce CO2 emission. However, the system has several barriers for the wider application such as high installation costs, incompletion of design standard and lack of recognition as heating and cooling system. In order to solve the problems, the energy-foundation system was developed by several researches which use building foundation as a heat exchanger. Although many construction companies have more interest in various types of energy-foundations, there are few researches on the design method. In this study, in order to establish the optimum design tool of an energy-foundation system integrated with the horizontal heat exchanger, the prediction method of ground heat exchange rate was developed with numerical simulation model. The developed model was coupled with ground heat transfer model, ground surface heat model and ground heat exchanger model. Furthermore, case studies on prediction of heat exchange rate (HER) have been conducted at different conditions of design and installation with variables such as pipe spacing, installation depth, pipe diameter, circulation water temperature, flow rate, and operation condition. The HER for each case study has been calculated based on the long-term simulation. (C) 2014 Elsevier Ltd. All rights reserved.