Development of microclimate modeling for enhancing neighborhood thermal performance through urban greenery cover

Green spaces and vegetation cover offer various environmental benefits, including building energy-saving. Enriching the urban vegetation is fundamental in urban heat island (UHI) mitigation policies promoted over the last years in many large North American cities. For example, the Greater Toronto Area (GTA) has been promoting significant increases in urban greenery by intensifying the urban trees and green roofs. In this paper, an updated version of the open-source code of the Urban Weather Generator was developed and validated to assess the effect of the increased horizontal and vertical green infrastructure on the microclimatic thermal performance of three urban typologies within the GTA. The updates of the model efficiently estimate the cooling and warming effects of the urban greenery cover on the microclimate thermal environment. The proposed enhancements included intensifying the tree canopy and incorporating the vegetated façades and green roofs. The validation ensured the model's ability to predict the cooling and warming effects of the green infrastructure. The results confirmed that tree canopy and green façades were the most effective mitigation strategies for reducing the canyon air temperature and building energy consumption, respectively. A parametric analysis utilizing a multi-objective algorithm was also designed to evaluate the effectiveness and affordability of the applied strategies. The results showed that the ambient peak air temperature, the outdoor heat stress index, and building energy savings were reduced by up to 4.6 ˚C, 5.4, and 42.4%, respectively. Considering reducing the green infrastructure cost by 50%, the parametric study resulted in a reduction of up to 3 ˚C, 2.9, and 35.6% in the ambient peak air temperature, the outdoor heat stress index, and building energy savings, respectively.