The EU’s Renovation Wave, EPBD, and national laws exempt listed buildings from mandatory energy performance standards, thus limiting incentives for efficiency improvements despite their poor energy performance. This exemption presents challenges for homeowners striving to reduce energy consumption and costs while preserving architectural integrity. This study evaluates energy performance improvements and associated renovation challenges in 11 comprehensively renovated heritage residential buildings. On average, the energy performance improved by 31%, and heating demand was reduced by 43%. Findings indicate that pre-renovation structural damage was common, necessitating repairs. Over half of heat loss occurred through external walls and windows, making these components primary targets for renovations. However, heritage homes still exhibited approximately twice the energy consumption of new buildings due to inadequate insulation and outdated service systems. Mechanical ventilation with heat recovery proved essential for improving energy performance and indoor climate but was often neglected. The study suggests that energy performance could have been improved by an additional 20% without compromising heritage values. Although heritage conservation outcomes were largely positive, substantial improvements are necessary to optimize lifecycle costs, environmental impact, user comfort, and long-term technical sustainability.