Technologies for Energy Retrofitting Supported by Exoskeletons to Reinforce Historic Buildings. A Case Study Focused on Mitigating Summer Overheating

Historic buildings represent a significant portion of the architectural heritage in Europe and Italy, requiring careful design that considers a multitude of aspects and constraints. The main challenge lies in finding a balance between preserving historical value and implementing innovative solutions that enhance structural and energy performance. In recent years, use of structural reinforcement technologies, such as exoskeletons, combined with energy-efficient solutions, such as transparent double-skin façades (DSFs), has become increasingly common. This combination of technologies shows a positive effect in winter season, due to greenhouse effect created in the cavity. However, there is a lack of studies on its summer performance, and considering the ongoing climate change, solutions that can prevent buildings from overheating are necessary. In this context, the proposed study explores the coupling of a structural exoskeleton with a transparent double-skin façade, with a specific focus on summer performance, for a building located in Rome. Different glazing types, with different thermal transmittance, solar heat gain coefficient, solar transmittance and visible transmittance, are proposed and compared. Moreover, the ventilation rate inside the cavity is examined. Low-emissivity glass panes are the best for the winter season, thanks to their property of reflecting the internal heat preventing thermal losses, while reflective glasses are the best for the summer season, due to their ability to reflect incident solar radiation, avoiding excessive overheating of the cavity. As regards ventilation, it appears that a number of openings sufficient to ensure an air exchange of 15 vol/h is enough to ensure maximum heat dissipation.