Smart Skin for Zero Energy Buildings: A Review of Thermoresponsive Spectral-Adaptive Envelopes.

Buildings are increasingly being conceived as dynamic systems that interact with their surroundings to optimize energy performance and enhance occupant comfort. This evolution in architectural thinking draws inspiration from biological systems, where the building envelope functions like a thermally responsive "skin" that can autonomously adjust its optical and thermal properties in response to environmental temperature changes. Among the many approaches developed for smart building envelopes, passive thermoresponsive spectral modulation systems have attracted growing interest due to their structural simplicity and low energy demand. By dynamically tuning solar radiation transmission and thermal emission across different spectral ranges, these systems reduce the reliance of buildings on mechanical heating, cooling, and lighting, thereby enhancing overall energy efficiency and climate responsiveness. This review offers a comprehensive and unified perspective on thermoresponsive building envelope technologies, bridging transparent and opaque components-including thermochromic smart windows and tunable radiative wall coatings-within the architectural context. It places particular emphasis on multiband spectral control, material-structure integration, and performance under diverse environmental conditions. Finally, it outlines key challenges and future research directions in advancing spectral control capabilities, aesthetic integration, all-weather adaptability, user-centered design, and practical applicability of thermoresponsive envelopes for next-generation sustainable buildings.