Simplified Outdoor Thermal Comfort Assessment Using Urban Shade Maps

Assessing shading benefits in urban environments has often been a complex task. This study proposes a simplified method for evaluating outdoor thermal comfort using the RayMan regression model to calculate Physiologically Equivalent Temperature (PET) and Mean Radiant Temperature (Tmrt).

By comparing Solar Radiation Transmissivity (SRT) with the Leaf Area Index (LAI) of common tree species in Taiwan, the study identifies an average SRT value of 0.3 (range: 0.2–0.5). This value is incorporated into ArcGIS solar radiation simulations to adjust sub-canopy radiation, enabling the construction of urban shading maps and PET-based thermal comfort maps for sidewalks. Additionally, the study analyzes PET along selected pedestrian pathways to assess heat stress conditions.

The results reveal a strong correlation between PET values derived from the simplified model and those obtained using the RayMan model. Radiation, wind speed, and air temperature are identified as the primary climatic factors influencing thermal comfort in Taiwan. Furthermore, the strong relationship between SRT and LAI significantly enhances the accuracy of thermal comfort mapping.

This GIS-integrated approach effectively identifies shading deficiencies, evaluates shading benefits, and recommends comfortable walking routes. The findings demonstrate that strategic shading can lower PET by 1–2°C in urban outdoor spaces, highlighting the crucial role of shading in enhancing outdoor thermal comfort.