Neighbourhood energy concepts for mixed industrial and commercial sites can be developed by applying energy integration techniques. This study presents an application of these techniques on a concrete site (RTA facility in Vienna, Austria), focussing on the possibility to recover the heat rejected from an industrial cooling process to heat a number of office buildings. The data set provided allows for characteristing the heat rejected and modelling the heat recovery possibilities by the help of composite curves. The data characterising the waste heat and the heat demand represented by these curves is generated by a Montecarlo simulation at a hourly time step. The parameters characterising the size of heat recovery and storage equipment are the decision variables of a thermoeconomic objective function which is minimized towards minimal energy costs for the buildings. This analysis leads to the optimal design of heat exchanger and thermal storage. The results show that 35% of the energy costs of a passive building can be saved under such conditions. However, the investments are not profitable for a conventional office building which requires heat at a higher temperature level. This study therefore introduces the need for a further analysis which would take into account the refrigeration requirements on the industrial side and propose an energy system design while taking into account the energy costs of the entire site (office buildings and industrial facility).