Effect of Green Roofs on External Microclimate and Runoff Mitigation: Do They Work in Historical Contexts? A Case Study in Naples

In cities characterised by a dense urban fabric and high population density, the lack of green spaces is a critical problem, despite their well-known environmental and social benefits. However, the creation of new green spaces for public use is often complex. This study proposes an innovative solution by creating a green roof on the internal terrace of SS. Apostoli, an art high school in the historic centre of Naples. The analysis was carried out using a framework that integrates the parameters of technical-environmental feasibility that are related to the baseline scenario, and the design variables related to substrate and vegetation of the green roof. The design of the greening strategy was validated through urban microclimate simulations, assessing its impact on air and surface temperatures, as well as through calculations of rainwater management, evaluating its effectiveness by analysing retention times and storage capacity in response to low permeability of urban soils. The results show a significant improvement in terms of temperature reduction and stormwater management. The chosen approach is a pioneering model that can be replicated in similar urban contexts and shows that greening strategies, if carefully planned, can integrate sustainable solutions without compromising the historical-architectural value of the buildings on which they are applied.