Amin Habibi, Romina Tafvizi, Mohammad Nikkar, Ehsan Sharifi,
Volume 34, Issue 2 (4-2024)
Abstract
Urban densities are prone to the urban heat island (UHI) effect, resulting in decreased outdoor thermal comfort for the growing urban populations in hot and dry climates. Canyon layout, surface materials, green cover, and ground moisture can alter the outdoor microclimates of urban canyons at the canopy layer. While the isolated impact of urban cooling strategies is researched extensively, the integration of these UHI mitigation strategies into design compositions for complex projects has yet to be thoroughly examined. This study explores the impact of six different design scenarios for the redevelopment of the entry canyon for the Afifabad garden in Shiraz during the hottest and coldest times of the last decade. The design scenarios include the final proposed and past layouts of the site, along with four interim scenarios introducing feasible compositions of greenery and cool surfaces.
The ENVI-met model of the site is validated by field measurement data from 2021, and then used to simulate all six scenarios for the hottest and coldest days of a typical year. The predicted mean vote (PMV) and physiological equivalent temperature (PET) values were calculated from the simulation results and evaluated to identify the most feasible and impactful design compositions. Findings indicate that high albedo pavements were not effective in isolation (scenario 4) and led to an increase in the mean radiant temperature (MRT). Street trees and vegetation were the most influential isolated measures, resulting in a 2.61°C variation in PET. The most impactful results were related to the combined effect of trees, turf, and cool surfaces, which resulted in up to an 11.3°C variation in PET due to the combination of appropriate greenery, shading over surfaces, and cool covers. Understanding the details of the impact of design configurations, when addressing heat stress adaptation in cities, enables the implementation of UHI mitigation strategies into feasible urban retrofit and regeneration projects.
