We present results of building performance simulations coupled with borehole heat exchanger (BHE) simulations for modeling the response of BHE-fields to varying heating power demands. We apply this method to an existing settlement in the Lower Rhine Embayment in Germany, called Neu-Teveren. Buildings in this former military settlement were built in the 1950s and will be extensively retrofitted in the coming years. Thus, it is a prime opportunity to model the impact of retrofitted buildings on the performance and longevity of BHEs. Our simulation results based on multi-year outdoor temperature records show that the cooling effect of the BHEs in the subsurface is about 3 K lower for retrofitted buildings. Further, a layout with one borehole heat exchanger per building can be efficiently operated over a time frame of 15 years, if the BHE-field layout considers regional groundwater flow. Due to northward groundwater flow, thermal plumes of reduced temperatures develop at each BHE, showing that BHEs in the southern part of the model affect their northern neighbors. Changing the layout of the BHE-field increases the performance of individual BHEs.