A Novel Framework for Heat Stress Risk Assessment and Mitigation in Real and Typological Historical Public Open Spaces Under Climate Change Scenarios

Climate change is altering the use of public open spaces in historical urban environments, compounded by urban heat island effects. Especially considering urban squares, rising temperatures increase health risks for outdoor users, particularly for vulnerable individuals (by, e.g., age and fragility). Rapid risk assessment under current and future climate scenarios can exploit integrated simulations to support the process, considering both real-world environments and Built Environment Typologies (BETs), which represent the recurring morphological, constructive, and material features of such urban squares. Simulation-based approaches can also support the assessment of mitigation strategies considering sustainability, reversibility, visual integration, and compatibility with the heritage. This work proposes a framework for simulation-based heat risk assessment of outdoor users under current and future (2050 and 2080) overheating scenarios and considers pre- and post-mitigation conditions of urban squares. Outdoor temperature conditions are simulated using ENVI-met, enabling the multiscale assessment of users’ heat stress and thresholds in exposure timings before critical dehydration. The approach is applied to two Italian historical urban squares in Bari and Naples, and to their associated BETs. The results highlight the framework’s capabilities in addressing the impact of climate scenarios and pre-/post-mitigation conditions, considering the local and global conditions of the urban squares. Moreover, the observed similarities between POSs and their corresponding BETs demonstrate that these archetypes can support preliminary risk assessments, providing decision makers with a rapid overview before adapting analyses and mitigation strategies to the specific characteristics of each urban square.