Evaluation of a simulation system for ecological strategies for outdoor comfort: a case study on the UNIPA University Campus in Palermo

The intensification of the urban heat island effect and growing thermal stress in Mediterranean contexts necessitate the adoption of effective Nature-Based Solutions, among which green walls stand out for their ability to mitigate thermal stress on vertical surfaces in densely built environments. This study analyzes the microclimatic effectiveness of a vegetated facade through the application of the ENVI-met three-dimensional simulation software, using the University of Palermo campus as a case study. The research integrates an in situ microclimatic monitoring phase, conducted during summer conditions, to collect real-world data on air temperature, relative humidity, and solar radiation for calibrating the numerical model. Such calibration is essential to reduce discrepancies between observed and simulated values, ensuring reliable results when evaluating intervention scenarios. The comparison between the current site configuration and the design scenario highlights that the integration of a green wall on the west-facing facade produces tangible improvements in outdoor comfort conditions at the pedestrian level. Simulation results indicate a reduction in air temperature of approximately 1 °C during peak afternoon hours of maximum thermal load, together with a notable decrease in mean radiant temperature due to the combined shading and evapotranspiration effects of the vegetation. These variations are positively reflected in the Predicted Mean Vote index, which shows a transition from moderate thermal discomfort toward more neutral conditions. The study confirms the validity of ENVI-met as a decision-support tool, demonstrating how even localized vertical greening interventions can effectively improve the urban microclimate and enhance the usability of institutional open spaces.