Investigating the role of residential configurations in shaping outdoor thermal comfort in hot, arid climates.

Urban morphology plays a pivotal yet underexplored role in mitigating urban heat. This study investigates the impact of geometric configurations of three typical residential neighborhoods in Tehran, Iran, on outdoor thermal comfort (OTC) using computational fluid dynamics (CFD) simulations conducted with the ENVI-met model. The dynamic thermal comfort (dPET) index was used to assess pedestrian thermal comfort, focusing on the following vulnerable groups: children and the elderly. Meteorological measurements, including air temperature, relative humidity, wind speed, and mean radiant temperature, were obtained at each neighborhood site during July 1-3, 2024. These measurements were used to evaluate ENVI-met simulation performance by comparing observed to simulated data. We additionally examined the effect of a suite of adaptation strategies aimed at improving OTC through the following modifications: (1) raised material albedo to 0.5 and 0.75, and (2) added street trees with 50% and 75% fractional coverage. A final, maximum deployment scenario, incorporating 75% vegetation coverage and a material albedo of 0.75, was evaluated for all neighborhoods. Our analysis indicates that children could benefit from lower dPET values compared to the elderly during sunlit hours. However, both age groups benefit from enhanced OTC in high-rise neighborhoods. Maximum deployment of vegetation was highly effective in reducing dPET, particularly in high-rise configurations, with reductions of nearly 2 °C at noon. This study demonstrates the critical role of urban morphology and biophysical adaptation in shaping thermal environments and provides actionable insights for designing thermally comfortable and resilient urban spaces in hot and arid regions.