Beyond surface greening: four critical drivers of user satisfaction in office sky gardens across international and Chinese contexts

High-density office environments are increasingly associated with heat stress and mental health burdens. While sky gardens are proposed as a biophilic remedy, quantitative evidence linking specific design factors to occupant restoration across different urban contexts remains scarce. This study identifies critical biophilic drivers in office sky gardens and compares their performance through a mixed-methods approach encompassing expert audits of ten representative projects systematically distilled from 60 cases (international vs. Chinese), 240 structured user surveys, and 15 expert interviews. Statistical analysis reveals that international projects achieve significantly higher user satisfaction (p < 0.05), which is driven primarily by four critical factors: spatial vertical complexity, vegetation diversity, microclimatic comfort, and facility richness. These four drivers show strong positive correlations with stress reduction, perceived naturalness, and workplace productivity (r = 0.50–0.72). In contrast, Chinese cases frequently underperform because of a reliance on visually driven “surface greening” and strict maintenance constraints. Synthesizing these empirical findings, this study outputs a context-sensitive priority matrix and actionable design strategies. By quantifying these factor‒outcome relationships, we provide a replicable framework to optimize vertical greening for occupant health and urban resilience in diverse high-density settings.