This paper introduces a novel heating, ventilation, and air conditioning (HVAC) system in cold climates to meet thermal comfort with lower energy use than traditional systems. The smart HVAC unit is driven by a naturally driven free heating and cooling system using earth as a seasonal thermal reservoir to store/generate energy through 25 boreholes to meet the heating/cooling demands of an office building in Uppsala, Sweden. TRNSYS analyzes the system's performance, applying thermodynamic rules and lifecycle cost assessment. The results show that the air handling unit can meet more than 50% of heating and cooling demands. Despite high investment costs, the proposed system has a promising payback period of fewer than ten years, demonstrating the role of smart HVAC design. Considerably lower primary energy is used by recovering the free heating and cooling of 313 MWh from the ground, highlighting the effectiveness of utilizing the earth's stable temperatures.