The existing building stock in Italian historic centres predominantly comprises masonry aggregates constructed before the introduction of seismic design codes. These buildings often feature irregular geometries and low-quality materials, making them highly susceptible to seismic events. Understanding their structural behaviour is essential for developing effective and sustainable mitigation strategies that not only improve seismic performance but also meet the energy efficiency requirements outlined in recent European directives aimed at reducing carbon emissions. This study focuses on three municipalities in the Molise region, namely Baranello, Campochiaro, and Colle d'Anchise, analysed through the CarTiS survey form. A detailed typological and structural classification of the building stock was conducted, and a representative aggregate was selected in each municipality for in-depth mechanical investigation. Initially, the "as-built" condition of each aggregate was modelled. Subsequently, an innovative retrofitting solution was proposed: a lightweight aluminium alloy exoskeleton integrated with insulating sandwich panels. This intervention aims to enhance both seismic resilience and energy efficiency, offering a sustainable retrofit approach. Nonlinear static and dynamic analyses were performed using a macro-element modelling strategy to evaluate the structural response under seismic loading for both the original and retrofitted configurations. The results demonstrate the effectiveness of the proposed system, showing improvements in strength and stiffness and a significant reduction in displacements during seismic events.