This paper describes and demonstrates how to use the optimization program GenOpt with the building energy simulation program ESP-r. GenOpt, a generic optimization program, minimises an objective function that is evaluated by an external simulation program. It has been developed for optimization problems that are computationally expensive and that may have nonsmooth objective functions. ESP-r is a research oriented building simulation program that is well validated and has been used to conduct various building energy analysis studies. In this paper, the necessary file preparations are described and a simple optimization example is presented
