The separation between structural engineering and building energy research has limited the ability of urban studies to capture interaction-driven performance at collective scales. This study develops and applies an integrated structural–energy co-optimization framework at the urban block scale to evaluate the role of adaptive structural systems in reducing energy demand under humid subtropical conditions. Using a representative urban block composed of heterogeneous low- to mid-rise buildings in: content Reference[oaicite:0] {index=0}, the research couples reduced-order structural modeling with time-resolved energy simulation and rule-based adaptive control. Quantitative results demonstrate that coordinated structural and envelope adaptivity can simultaneously reduce block-level cooling demand and inter-story drift, revealing non-linear trade-offs captured through Pareto optimization. The findings confirm that block-scale coordination outperforms isolated building-level adaptation and that targeted intervention in dominant buildings yields system-wide benefits. The study establishes structural adaptivity as an active energy-modulating mechanism and provides a transferable methodological foundation for performance-driven sustainable urban design.