Outdoor thermal comfort by different heat mitigation strategies - a review

Due to the ongoing global warming, heat mitigation strategies are becoming implemented through practice and simulations. These efforts aim to make the cities that are dealing with the urban heat island more livable. The effect of heat mitigation strategies on climate condition and energy consumption have been studied and compared, previously. In this paper, the effect of these strategies on human thermal comfort in urban open spaces is reviewed. Specifically, the review is focused on vegetation (in the form of parks, street trees, green roofs and green walls), and highly reflective materials (on roof and on the ground level) as the most common strategies for improving the thermal conditions in cities. Several studies done by simulation or through field measurement in different countries are described. The most important finding of the review is the fact that although highly reflective materials reduce air temperature in urban open spaces, they increase the re-radiation of sun to the pedestrians. Therefore, vegetation is a better choice for improving thermal comfort in the pedestrian level