Eco-Efficiency of Green Infrastructure on Thermal Comfort of Outdoor Space Design

Trees and shrubs, as a part of the green infrastructure, are important for the well-being of urban dwellers. This research aims to study the eco-efficiency of trees on outdoor thermal comfort, defined by the ratio of the change in the physiological equivalent temperature (PET) and the trees' cost. Field data were collected and compared with station data to calibrate and create a base case model. After the base case model was created, the researchers created case scenarios with shrubs and trees occupying 25, 50, 75, and 100% of the space. The cost estimate was calculated by the price quotes from local providers. The results suggested that (1) trees and shrubs were confirmed to positively improve thermal comfort, especially in the late afternoon when it is the most uncomfortable, (2) adding more trees to the study site could increase the eco-efficiency values more than shrubs in all cases, and (3) adding trees at 50% coverage gave the highest eco-efficiency compared to the other options. The results of this exploratory study will provide an alternative design approach that helps in decision-making for outdoor spaces. Future studies should address plant selections and other ecosystem benefits that may affect the eco-efficiency calculation.