Evaluating UHI Mitigation and Outdoor Comfort in a Heritage Context: A Microclimate Simulation Study of Florence’s Historic Center

This paper evaluates Urban Heat Island (UHI) mitigation strategies in Florence’s historical centre, characterized by relevant cultural heritage value and significant tourist fluxes but increasingly susceptible to heatwaves. The research work focused on the evaluation of both current microclimate conditions and mitigation solutions for UHI-related issues, using ENVI-met microclimate modelling software as a simulation tool. Different models, featuring a 2 m grid resolution and detailed material properties, were produced to assess outdoor air temperature (Ta), mean radiant temperature (MRT), and Universal Thermal Climate Index (UTCI), chosen as reference parameters for human thermal sensation. Diversified conditions induced by the peculiarities of the urban layout were highlighted, with current Ta up to 32 ◦C and MRT exceeding 55 ◦C in paved open areas. Site-specific measures and their expected effectiveness were hence analyzed. De-paving and greening yield modest local cooling (Ta reduction up to −0.25 ◦C, MRT up to −1.75 ◦C), while tree installation ensures that MRT decreases by −7.50 ◦C to −12.00 ◦C. Most effectively, suspended shading fabrics preventing direct radiation can act on Ta (−0.09 ◦C to −0.25 ◦C) and provide substantial MRT reductions (−7.50 ◦C to −17.00 ◦C), significantly improving thermal comfort. The findings emphasize the potentialities of site-specific, reversible interventions in historic centres to combine climate adaptation and heritage preservation.