Linking Insolation Shadow Ratio with UTCI: Morphological Insights into Outdoor Thermal Comfort

Jie, Song, Yu, Liu, Juan, Ren, Bo, Liu, Jiang, Yupeng, Li, Yirong, Zhuo, Lei, Liu, Siyi

ISES Solar World Congress 2025 · Fortaleza, Brazil · 2025-11-03
Published by International Solar Energy Society (ISES)
DOI: 10.18086/swc.2025.08.13

Abstract

Outdoor thermal comfort is strongly influenced by solar exposure, yet few simple metrics effectively quantify shading performance. Building upon previous research that introduced the Insolation Shadow Ratio (ISR), this study extends its application by linking ISR to outdoor thermal comfort and urban morphology. Eighty residential sites in Xi’an were surveyed, and parametric models were generated in Rhino/Grasshopper. The Universal Thermal Climate Index (UTCI) was simulated using the Fiala multi-node model, while ISR was derived through Ladybugbased sun-path analysis. Five morphological indicators (BD, FAR, OSR, BGSC, BSC) were correlated with ISR and the proportion of comfortable UTCI hours (UTCI%). Results show that ISR negatively correlates with BD (r = - 0.64 to – 0.80) and exhibits opposite seasonal effects: positive ISR – UTCI% relationships in winter/spring and negative ones in summer/autumn. The findings validate ISR as a simple and robust proxy for evaluating shading– comfort relationships and provide a quantitative framework for climate-responsive urban design.

Keywords

Outdoor Thermal Comfort, Outdoor Space, Insolation Shadow Ratio(ISR), Universal Thermal Climate Index(UTCI), Morphological indicators

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