Influence of built environment on outdoor thermal comfort: A comparative study of new and old urban blocks in Guangzhou

Urban populations face increasing heat stress in cities. However, the influence of the built environment of new and old urban blocks on pedestrian thermal comfort remains unclear. This study selected typical old (Yongqingfang) and new urban areas (Knowledge City) in Guangzhou, China, as our research sites. Through field monitoring and surveys, we used physiological equivalent temperature (PET) and thermal comfort vote (TCV) to evaluate outdoor thermal comfort by thermal walk experiments. We analyzed the relationships between built environment variables, meteorological variables, and pedestrian thermal comfort at the two sites. Our analysis revealed significant differences in the built environment and meteorological conditions between the new and old urban blocks within the 60-m buffer zone. PET and TCV showed noticeable spatiotemporal variations in both sites, and their correlation was stronger in the morning (r = 0.87–0.89) than late afternoon (r = 0.60–0.70). Our stepwise regression model indicated that sky view factor and building coverage ratio significantly affected outdoor thermal comfort in old and new urban blocks. Built environment variables explained a higher percentage of the variance in PET (Yongqingfang R2: 0.59–0.82, Knowledge City R2: 0.32–0.81) than TCV (Yongqingfang R2: 0.45–0.57, Knowledge City R2: 0.48–0.69). In short, built environment variables affected thermal indices more than thermal perception. The impact of built environment variables on TCV is also greater in new urban areas than in old urban blocks. Our findings provide insights into the complex relationship between built environments and outdoor thermal comfort in different urban landscapes, which informs climate-resilient urban design.