Design scenarios to mitigate positive thermal hot-spots in urban areas. The combined effect of green-blue-grey infrastructure in a public square in Florence (Italy).

The rapid expansion of urban heat zones, now extending beyond central districts into semi-central and peripheral areas, intensifies thermal anomalies and stress conditions in cities. This study explores the effectiveness of Green-Blue-Grey Infrastructure (GBGI) solutions in mitigating positive thermal anomalies and improving outdoor human comfort in a public square in Florence (Italy). The study area was characterized by extensive asphalt pavements and influenced by nearby commercial-industrial zones.

As part of the “Climate Change & Biodiversity” project, funded by the Capellino Foundation, this research aims to develop an interdisciplinary analysis approach to comprehensively study urban biodiversity and mitigate positive thermal anomalies in Florence.

Using geospatial tools like QGIS, ENVI-met and I-Tree, urban-climate modeling and microclimatic simulations were performed for the summer and winter solstices of 2023.

A comparison between the current thermal situation (ex-ante) and a proposed scenario (ex-post) was conducted, incorporating various elements such as vegetation, high-albedo surfaces, and permeable pavements to assess the impact on the local microclimate and relative thermal comfort.

Summer simulations revealed reductions in mean air temperature (up to 1.3 °C) and surface temperature (up to 13 °C), particularly during peak daytime hours. Outdoor thermal comfort, measured by the Universal Thermal Climate Index (UTCI), improved by an average of 3 °C in summer daytime, lowering heat stress from “strong” to “moderate” or “very strong” to “strong”. Winter simulations showed minimal adverse effects, preserving favorable conditions.

These findings highlight the GBGI’s effectiveness in reducing thermal stress and enhancing favorable microclimatic conditions, particularly in summer, while supporting biodiversity and multiple ecological benefits. This research offers actionable insights for urban planners and policymakers seeking sustainable solutions to address urban heat islands and improve the resilience of public spaces. Future research will focus on validating the simulated findings through in-situ post-implementation data to further refine and optimize urban cooling strategies.