Spatial thermal comfort autonomy (sTCA) for corridor–atrium buildings in cold-climate high-density contexts: UTCI-based multi-objective optimisation and sensitivity analysis

High-density, multi-storey atrium buildings are increasingly adopted in cold-climate regions of northern China, yet their interior corridors often exhibit strong seasonal thermal discomfort. Conventional point-based assessments fail to capture the space–time heterogeneity of corridor microclimates, limiting their design relevance. This study proposes a Spatial Thermal Comfort Autonomy (sTCA) indicator to quantify the percentage of corridor space–time states within an acceptable UTCI band (0–32 °C) on representative extreme days. A validated Universal Thermal Climate Index (UTCI) simulation workflow is coupled with NSGA-II (Wallacei) to optimise three objectives: maximising summer sTCA, maximising winter sTCA, and minimising overall cold–heat stress (TS). The optimisation evaluates 4500 configurations. Interpretable geometric descriptors, including atrium enclosure and plan proportions, corridor section and plan proportions, orientation, and vertical stacking, are used to analyse the solution space. Spearman screening and Type-III ANOVA with effect sizes identify dominant drivers and seasonal trade-offs. Atrium enclosure and corridor plan slenderness dominate all objectives, while orientation strongly modulates summer performance. Indicative near-optimal windows include atrium height-to-width ratio of 3.910–5.460, corridor plan slenderness of 76.880–84.910, and orientation offset of 79.250–85.000°. The sTCA–TS framework supports early-stage corridor–atrium design.