This research proposes the development of a diagnostic tool to separately inspect the energetic and seismic behaviour of buildings in the small hamlet of Baia e Latina (district of Caserta) in order to evaluate and implement retrofitting interventions from seismic, energetic, and functional points of view. Methods, approaches, and tools relating to the minimisation of seismic vulnerability and energy consumption have been increasingly used and tested in order to ensure both sustainability and safety, with a connection that may improve the performances of both cultural and environmental heritage. The diagnosis method, stemming from the energy audit and the energy imprint evaluations of the buildings system (and the envelope above all), aims to redesign the whole construction or some of its parts within an energetic framework. With reference to the seismic behaviour of building aggregates, the basic methodology that has been conceived for isolated masonry buildings through a survey form has represented the starting tool for the application of an appropriate quick evaluation form considered for the aggregated structural units of historical centres. Finally, the methodology employed is aimed at obtaining an Energy Performance Certificate for the structural units of examined masonry aggregates without neglecting their seismic behaviour, which has been assessed in terms of vulnerability and damage.