Winter outdoor thermal comfort in university campus open spaces in the cold region of China

• SVF and shading types interact, jointly influencing thermal sensation. • Developed a new thermal comfort evaluation model integrating SVF, PET, and TSV. • Created a winter "Space-Environment-Perception" timetable based on the new mode Outdoor open spaces on university campuses play a crucial role in influencing students’ physical activities and psychological well-being. This study was conducted on a university campus in Xi’an, a representative cold-region city in China, employing both on-site microclimatic measurements and questionnaire surveys. The research investigates the relationship between the Physiological Equivalent Temperature (PET) and subjective thermal perception (thermal sensation) in outdoor spaces with varying degrees of openness and shading types during winter. A comprehensive “spatial–environment–perception” evaluation model was established to quantitatively analyze the interactive mechanisms among spatial morphology, thermal environment, and human thermal perception. The results indicate that the neutral PET (NPET) of campus outdoor spaces in Xi’an is 26.3°C. The Sky View Factor (SVF) exhibits a quadratic relationship with PET, reaching a minimum value of 6.99°C when SVF = 0.53. Moreover, SVF and shading type jointly exert interactive effects on thermal sensation votes, with greening-dominated shading spaces consistently achieving the most favorable thermal perception across all SVF levels. The multivariate evaluation model further reveals that NPET also follows a quadratic relationship with SVF, elucidating the coupled influence of spatial openness and thermal environment on outdoor thermal comfort in winter campuses.