Modelling of district heating and cooling (DHC) systems allows for optimized system design and operation. We present a novel thermo-hydraulic network model, which we apply to a large 5 th generation DHC network, coupled to a horizontal ground heat exchanger. We use Co-Simulation with finite-volume models in order to account for heat gains of both, the ground heat exchanger as well as the uninsulated network piping system. We found that the network contributes about 50 % of the source heat demand during the heating period, whereby it strongly varies over the course of the year. The model's simulation performance is relatively high as we reduce the number of pipe ground models by identify pipes with similar ground temperatures.