Key Performance Indicators (KPIs) can be used to measure a project’s effectiveness in achieving energy efficiency and environmental impact goals. This contribution uses a set of defined KPIs for application to a historic building renovation in Rome, addressing conservation needs. The KPIs emphasize sustainability across Political, Economic, Social, Technological, Environmental, and Legislative domains (PESTEL). Findings show that only three KPIs are unmeasurable due to data limitations, while three are partially defined. The remaining 19 KPIs were fully assessed, highlighting their importance in renovation projects aligned with legislation like the “Energy Performance of Buildings Directive”. This legislative frameworks, as well as other directives, focus on metrics such as energy reduction, carbon footprint minimization, and indoor environmental quality. These KPIs help stakeholders implement strategies that meet legal standards and promote sustainability. Since the case study have been rated as LEED Platinum and “Very Good” score for BREEAM, this study also emphasizes the connection between developed KPIs and existing certifications. In particular, KPIs assessing the “cultural heritage” aspects are not linked to any “Section” criteria in BREEAM, highlighting a gap where socio-cultural considerations could enhance certifications. Additionally, KPIs can guide research for innovative construction materials and methods, including renewable energy adoption and advanced insulation technologies. Calculating these KPIs provides a comprehensive assessment of renovation projects from pre- to post-intervention phases. Establishing a clear KPI framework allows integrating additional metrics, ensuring thorough evaluations and promoting sustainable development in the construction sector while preserving historical integrity.