Historic buildings - that strongly characterize European cities and determine unique historical centers and downtown - must actively contribute to achieve the goal of decarbonization of the building sector by 2050, being not negligible because of their number, use and presence, in Italy. The energy retrofitting processes of such buildings often face constraints related to preserving historical, architectonic and artistic value, which limits the possibilities of intervention. This study, starting from a review of the state of the art in the matter of energy efficiency of historic buildings, identifies and classifies the commonly implemented strategies and technologies, proposing a relevant method to select retrofit packages. The identified configurations are then applied, when suitable, to some representative historic case studies, to perform a cost-optimal based retrofit approach, selecting suitable interventions, on the basis of a sensitivity analysis concerning single or multi-family buildings, geometric characteristics (e.g., surface-to-volume ratios, opaque/transparent ratios) and uses. The interventions will be implemented while respecting artistic and/or architectural constraints.