Investigation into the outdoor thermal comfort on different urban underlying surfaces

Changes in urban microclimate are closely related to the nature of the urban substratum and are a key factor in the formation of urban heat islands and an important factor affecting the urban thermal environment. In outdoor space, the human body is close to the ground, and ground radiation significantly affects mean radiation temperature. However, the effect of ground radiation may vary due to differences in environment and materials. To investigate the thermal comfort of different underlayment surfaces under outdoor thermal radiation, this study conducted subjective questionnaire research and field measurements of objective parameters on the radiation characteristics of four other underlayment surfaces and their personnel thermal comfort. It came to the following three conclusions: 1) In sunny weather, with the increase of thermal perception and solar radiation, the radiation gradually exceeds the temperature as the main factor affecting personnel thermal perception; 2) MRT is the main factor for the difference in personnel thermal perception at the same temperature. For different albedo underlayment materials, the change in personnel thermal perception is not the same for every 1 C-degrees change in MRT; 3) The neutral physiological equivalent temperature of different underlayment surfaces ranked as asphalt > grass > concrete > limestone, which was the opposite order of reflectivity of underlayment surface. Materials with higher reflectivity and lower solar radiation absorption rates should be considered when selecting outdoor underlayment surfaces.