Ground-source heat pump systems that collect energy from thermal borehole fields can produce heat independent of the outdoor temperature, making them ideal for heating cold climates. To reduce the risk of boreholes freezing due to excessive heat drain, the boreholes must be spaced far enough apart from each other. This requires space on the ground, which can be a great challenge in urban environments with limited plot sizes. This study looks into the potential of using residential waste heat to reduce the space requirements of ground-source heat pump systems while maintaining the long-term borehole field temperatures. In addition to conventional air-to-air ventilation heat recovery during the heating season, ventilation heat was also recovered in summer using a liquid-loop connected to the borehole fields. Similarly, sewage heat recovery was connected to the same loop. Hourly heating demand for a new apartment building in Finland was estimated using the IDA-ICE simulation tool. The various heat recovery schemes were modelled in TRNSYS 18. Two sets of similar simulations were completed: one for a single building case with a small borehole field and another for a block of buildings with a large borehole field. Widely spaced borehole fields were compared to tightly spaced borehole fields, to see how the ground temperatures and heat transfer fluid temperatures change over five years of operation. Without waste heat utilization, the tightly spaced borehole fields suffered from rapid temperature reduction. This problem was exacerbated in the large borehole field, due to having less natural regeneration as a result of a lower surface-to-volume ratio. However, when both ventilation and sewage heat were actively fed into the borehole field over the whole year, the ground temperature levels were stabilized and the fluid outlet temperatures remained above 0 °C.