A systematic and well-structured approach to preserving heritage buildings is essential for their restoration. This paper explores the integration of historic building restoration with sustainability, aiming to establish an effective methodology that addresses the restoration of historic buildings and their sustainable renovation, particularly regarding energy efficiency. The primary method employed in this study involves observing and analysing the restoration and utilisation of a historic building, with a specific emphasis on improving energy efficiency and conservation. The research concentrates on the Žica Monastery’s Dining Room, exploring the outcomes of the restoration process to ensure energy refurbishment and the enhancement of cultural heritage. The paper concludes with recommendations for the restoration and adaptive reuse of historic buildings, aligning with contemporary standards for comfort and environmental conservation while maintaining the authentic appearance of the structure.