Built heritage light retrofit enabling energy-efficiency and affordable housing: the case study of Quarticciolo in Rome

Europe faces converging crises - climate change, demographic shifts, energy insecurity - compounded in Italy by a building stock where 80% of structures predate 1990. European strategies such as the Renovation Wave and the Energy Performance of Buildings Directive target an 11% reduction in energy consumption by 2030, while addressing housing needs and energy poverty. This paper presents ongoing research on sustainable regeneration of social housing through a light- retrofit approach. Unlike deep-retrofit, light retrofit employs low-tech solutions that improve energy performance and housing quality without relocating residents, spreading interventions progressively to reduce disruption and costs, while ensuring decarbonization. Through a critical review of best practices in the European context, the research identified design strategies capable of implementing passive bioclimatic solutions and integrated technological systems. These are then transferred on a pilot case - the ERP Quarticciolo district in Rome, a protected 1940s social housing neighbourhood – in four scenarios of progressive intervention, that incorporate an exoskeleton, add-ons, infills, upward extensions to expand affordable housing supply - including student, senior, and co-housing - and recalibrate unit sizes, in response to evolving demographic demand. The findings demonstrate the feasibility of energy-efficient, low-tech and low-carbon renovation in architecturally significant urban fabrics, allowing to combat energy poverty, decarbonize and increase affordable housing supply.