A ground-source heat pump system was installed in a passive house near Poznan, Poland, to improve energy efficiency. By integrating a heat exchanger with the system, waste heat from outside air is captured and stored in the ground during summer, while also heating the supply air in winter. This setup increases the system's efficiency and saves energy, leading to significant cost and environmental benefits. The study showed that recovering heat from ventilation air in summer boosts the heating system's performance in winter, resulting in substantial energy savings. The approach has potential for both small and large-scale installations using ground-source heat pumps.