# BEST--Building Energy-Saving Tool for Sustainable Residential Buildings
## 6 Conclusions and Future Developments  
The current condition of the European residential building stock is marked by widespread obsolescence, inadequate thermal insulation, and high energy consumption, making it one of the primary contributors to greenhouse gas emissions in the built environment [5]. Energy retrofitting buildings within the European Union would result in substantial energy savings and a 26% reduction in energy consumption [45]. In Italy, the initial regulation aimed at reducing energy consumption in buildings was introduced in 1976 (Law 373/1976) [46]; however, it was characterized by limited restrictions and was frequently neglected due to insufficient enforcement mechanisms. It was not until 1991 (Law 10/1991) that the first comprehensive code targeting thermal performance standards was established, by which time more than 80% of the existing residential building stock was already constructed [47]. As a result, a substantial portion of Italy's residential properties continues to exhibit high energy consumption levels [20]. Therefore, a significant portion of the residential building stock is in urgent need of deep renovation to meet current energy performance standards and contribute to the EU's decarbonization goals. Renovation efforts must prioritize thermal insulation, modernization of HVAC systems, and the integration of renewable energy sources in order to reduce both energy demand and greenhouse gas emissions [48]. These buildings are often characterized by outdated construction techniques, inefficient HVAC systems, and poorly performing building envelopes. This context highlights the pressing need for scalable, accessible, and standardized retrofit strategies capable of supporting the transition toward nearly zero-energy buildings (nZEBs) and, in the longer term, positive energy buildings. In response to this challenge, the BEST was developed as a decision-support instrument designed to simplify the preliminary energy analysis and the selection of retrofit solutions for residential buildings. Through the classification of typical building envelope components and the integration of optimized, pre-calculated interventions, the tool offers practical guidance to designers and stakeholders, significantly reducing the complexity usually associated with energy performance assessments. Its application to a representative case study from the Italian residential context demonstrated the tool's effectiveness in identifying sustainable and cost-efficient interventions, with measurable benefits in terms of energy savings, CO\({}_{2}\) emissions reduction, and economic return. Future developments aim to extend the application of the tool to other building typologies, thereby broadening its scope and enhancing its contribution to the sustainability of the built environment as a whole. The potential of the tool extends beyond individual building analysis. Upcoming developments of BEST will include the integration of geo-referencing functionalities, enabling the spatial mapping of energy performance levels across the national building stock. The integration with GIS platforms will allow the identification of territorial clusters with poor energy performance, supporting data-driven decision-making and the strategic allocation of public resources. This approach may serve as an effective instrument for urban and energy planning at the municipal or regional scale. Moreover, the scope of the tool will be expanded to simulate interventions on building systems, particularly the replacement or upgrading of existing HVAC systems. Given that these systems account for a substantial portion of a building's overall energy consumption,their inclusion will enable a more holistic assessment of retrofit strategies. This evolution will enhance the tool's capacity to estimate comprehensive energy savings and provide a more robust basis for investment decisions.