In Italy, and across Europe and the Mediterranean area, a large number of existing masonry buildings are highly vulnerable to seismic activity. Constructed decades ago without accounting for seismic forces, these aging structures now fall short of modern technical standards and urgently require a robust consolidation plan. This plan must address not only seismic strengthening, but also improvements in energy efficiency, as many of these historic buildings experience significant thermal losses. Recent European directives emphasize reducing energy consumption in the building sector—responsible for over 30% of CO₂ emissions—and call for enhanced thermal performance. In this context, integrated seismic-energy retrofit systems have become one of the most promising solutions, simultaneously improving seismic resilience and energy efficiency in masonry buildings. This paper compares the seismic performance of a masonry aggregate and two of its key structural units, both before and after implementing an innovative, lightweight integrated seismic-energy retrofit solution. The proposed system combines an aluminium alloy base frame with insulating sandwich panels. Evaluations consider the external coating as a localized and comprehensive intervention, following current Italian Technical Code provisions, to determine which approach provides the most substantial benefits for structural safety and energy efficiency.