Achieving carbon emission reduction targets in historic structures is problematic: conventional efficiency measures can damage cultural heritage and uncertainties in early-stage analyses may undermine the reliability of the results. A decision framework capable of weighing economic, environmental and invasiveness factors—while acknowledging data uncertainty—is therefore essential. This study develops a fuzzy multi-criteria decision-making workflow that integrates dynamic simulation with advanced fuzzy Multi-Criteria Decision-Making (MCDM) techniques (fuzzy MULTIMOORA). Triangular fuzzy numbers are used to encode early-stage imprecision in costs, emissions and verbal assessments of impact on heritage; expert‐derived fuzzy Analytic Hierarchy Process (AHP) supplies criterion weights. The three rankings obtained from the application of the three approaches of which MULTIMOORA method is composed are merged through Kendall aggregation, providing a single, robust preference order. The procedure is demonstrated on an early 1900s office building in southern Italy. Seventeen energy retrofit measures are evaluated, which combine actions on the building envelope and the HVAC (Heating, Ventilation and Air Conditioning) system. Low-intrusive energy retrofit measures (for example, attic-side roof insulation and a new heat-pump based HVAC system), achieve considerable lifecycle-CO2 emissions cuts with contained costs, minimal conservation impact, and consequently occupy the top positions. Retrofit measures based on thermal insulation of exterior walls score good energetically but fall in the ranking owing to very-high heritage conservation penalties. The proposed workflow thus offers a transparent, uncertainty-aware roadmap for staged, conservation-compatible decarbonization of historic buildings.