This paper presents the process life cycle approach to the problem for retrofit of heat exchanger network (HEN). The main objective of HEN retrofit is to find the most economic way of reducing energy consumption in an existing network. However the HEN retrofit has to be considered in the life cycle context, i.e. simulation, conceptual design and detailed design. The first step when performing such a study is the extraction of data from an existing flowsheet to use in the conceptual design of HEN retrofit. The second step is to perform the HEN retrofit, i.e. to find a modification that reduces the energy consumption in the most economic way. Once an option for reduction in heating demand has been identified, the detailed design on heat exchangers that require additional area is performed. It is possible to automate these steps due to advances in software technology and a better understanding of the problem. Typically each step in HEN retrofit project is performed using individual software. The transition from one step to another requires both the flow of data and of knowledge. In our work, a set of rules and logic is used to automatically transfer knowledge between the steps. A design engineer is in complete control both within a step and during the transition from one step to another. A brief description of the existing methods will also be discussed. This will help to understand the strength of the proposed automated procedure in the context of life cycle analysis.