This paper describes a new automated procedure for retrofit heat exchanger network (HEN) design which aims to minimise modifications to the existing HEN structure. The new procedure employs a two-stage approach for retrofit HEN design, consisting of a modification selection stage and an optimisation stage. During the modification selection stage a minimum number of promising HEN topology modifications is obtained to enable a desired heat recovery target to be achieved. The resulting HEN is then optimised during the optimisation stage, using non-linear optimisation techniques, to minimise the cost of additional surface area employed.