Evaluation of microclimate mitigation strategies in a heterogenous street canyon in Kuala Lumpur from outdoor thermal comfort perspective using Envi-met

Assessing the efficacy of mitigation measures for the improvement of the daytime microclimate has been advised extensively, especially in hot and humid tropical regions as an effort to a) reduce the cooling demand of buildings and b) enhance outdoor livability by improving the thermal comfort of pedestrians. The latter has been investigated in this research based on microclimatic and urban characteristics of a developed commercial street in Kuala Lumpur, Malaysia and by utilization of field measurements and parametric simulations. The evaluated area is within a street canyon with heterogeneity in its urban components and building design with various heights and facade materials; being distinguished from the uniform or open-set urban complexes which had been assessed in the previous studies. Five mitigating scenarios were adopted using Envi-met V4.6 simulation software to investigate their influence on air temperature (Ta), surface temperature (Ts), mean radiant temperature (Tmrt), and physiological equivalent temperature (PET) in the study area during peak hours of the day from 11:00 to 16:00. Among the high albedo facade, high reflective ground surfaces, permeable pavement, extra tree coverage, and a mixture of the last two measures, it is identified that the application of permeable pavements and added tree resulted in maximum PET improvement along with Ta, Tmrt, and Ts reductions. The study also shows that increasing the albedo of facades despite a negligible impact in reducing Ta, causes PET to worsen; the same results were obtained regarding high reflective pavements and roads, although significant Ts reduction occurred through this method. The research concludes that considering the tropical climate of Kuala Lumpur with abundant solar radiation and rainfall, for narrow streets with variation in components and high-rise buildings, implementation of permeable pavement on sidewalks and open parking areas not only contribute to alleviating urban warming effects but can potentially manage stormwater runoff as well.