The effect of green stormwater infrastructures in urban tier human thermal comfort—a case study in high-density urban blocks

Abstract Using green stormwater infrastructure (GSI) is the main method of greening and cooling high-density blocks. Many studies have been conducted to evaluate the effect of a single GSI on thermal comfort on sunny days. However, GSI often occurs in combinations, and assessment of GSI cannot ignore the effect of rainwater on the thermal comfort improvement. Therefore, based on measured data of a real urban area of Nanjing, China, this study used 45 GSI single and combination simulation scenarios and three local climate zone (LCZ) baseline scenarios to compare and analyze three high-density blocks in the city. The physiological equivalent temperature (PET) was calculated using the ENVI-met specification to evaluate outdoor thermal comfort. The study produced the following results. (1) To improve outdoor thermal comfort, compact high-rise and mid-rise areas require more abundant GSI combinations, but only using a single GSI can have a good effect in compact low-rise area. (2) In extreme high-temperature weather, rainfall is a necessary condition for improvement of thermal comfort by GSI, and complex GSI can extend the thermal comfort improvement time following rainfall by more than 1 hour. (3) To improve the thermal comfort of a potential area of outdoor crowd activity to the greatest extent, shading and tree setting should be added based on the premise of increasing the combinations of GSI, and the efficiency of improvement can reach as high as 54.23 %. The results of the study indicated that future GSI construction in high-density blocks should focus on different combinations of GSI based on different LCZs. This conclusion provides a reference for other regions in Southeast Asia, where GSI construction systems should be studied and formulated in accordance with different LCZs.