This study focuses on the design of a heat source based on renewable energy technologies integrated with a large-scale heating and cooling system for a multifunctional building. The building is located in Žilina, Slovakia, where the outdoor design temperature reaches as low as − 15 ℃. A comprehensive energy analysis was conducted, evaluating heat losses and gains in accordance with current European legislative standards and building energy performance regulations. The proposed solution utilizes an air-to-water heat pump as the primary source of both heating and cooling energy. This system is designed to meet the thermal demands of the building while minimizing environmental impact and operational costs. The heat distribution system consists of ceiling panels mounted on a steel structure, which serves as a support for gypsum plasterboard cladding. This configuration ensures efficient thermal transfer and integration with the architectural design. Several alternative heat and cooling sources were considered during the design phase, including ground-source and water-source heat pumps. However, following a detailed comparison based on energy efficiency, economic feasibility, and environmental impact, the air-to-water heat pump was selected as the optimal solution. The building’s heating demand was calculated to be 33.6 kW, while the cooling load was determined to be 35.5 kW. The selected heat pump is equipped with two compressors, allowing for modulation of output under partial load conditions, thereby improving efficiency and operational flexibility. To ensure reliable performance during periods of extremely low outdoor temperatures, two electric flange heaters installed in a storage vessel are proposed as a backup heat source. The system design aims to provide a sustainable, cost-effective, and resilient solution for year-round thermal comfort in a multifunctional building.