Scaling Positive Energy Districts Through Integrated Active Exoskeleton Retrofits: A REC-Driven Application to a Social Housing Cluster

The transition toward climate-neutral cities requires large-scale building retrofits combined with collective renewable self-consumption. This study assesses the energy performance of en-SOLEX, a modular solar exoskeleton retrofit system, applied to a social housing district in Bari (Italy). The system transforms energy-intensive buildings into net-positive producers while increasing self-consumed electricity, improving the feasibility of Renewable Energy Communities (RECs), particularly in social housing contexts where energy sharing can reduce energy poverty. When integrated within a REC, en-SOLEX significantly enhances collective self-consumption and mitigates increased demand from electrification. The self-consumption index (SCI) rises from 65% in a rooftop PV scenario to 74-91% with en-SOLEX, reaching up to 98% under electrified conditions. The self-sufficiency index (SSI) also improves, achieving up to 43% in non-electrified cases and remaining positive under full electrification. Compared to diffuse rooftop PV, concentrating generation on selected buildings reduces structural constraints, minimizes retrofit interventions, and simplifies decision-making, key barriers in social housing RECs. Overall, the study shows that combining deep retrofits, façade-integrated PV and REC-based energy sharing provides a scalable and inclusive approach to achieving Positive Energy Districts that are aligned with EU decarbonisation targets.