Evaluation of Downtown Urban Spaces Under Cold Climate Conditions Using Thermal Indices for Climate-Responsive Design: A Case Study of Sapporo, Japan

Urban thermal comfort in winter is an important but insufficiently quantified component of sustainable, climate-adapted urban design in cold-weather cities facing energy-intensive winter environmental challenges. This study uses high-resolution simulations to evaluate discomfort across a downtown district in Sapporo, Japan, based on the standard effective temperature (SET*) index and universal thermal climate index (UTCI). A total of 2438 sampling points were assessed under 69 hourly winter scenarios. Discomfort hotspots were found in east–west streets and wind-exposed corners, driven by limited solar access or intensified wind. SET* is a more sensitive indicator under cold conditions, particularly in shaded areas. Wind speed and mean radiant temperature distributions revealed the environmental drivers of discomfort. The influence of building height was confirmed via quantitative correlation analysis, which revealed significant negative relationships between adjacent building heights and SET* across all streets analyzed, especially in east–west street canyons, where correlation coefficients ranged from −0.80 to −0.52 in the representative street. These findings contribute to urban sustainability by providing a quantitative tool for identifying winter thermal vulnerability and supporting passive, climate-adapted public-space design. The proposed framework can help improve winter walkability, outdoor activity, and the environmental quality of downtown spaces in cold-region cities.