Structural engineering of hierarchical aerogel-infused wood for synergistic daytime radiative cooling and fire safety

The building sector faces dual challenges of high cooling energy consumption and significant fire risks from conventional construction materials. To tackle these challenges, the present research devises an innovative wood-derived composite that simultaneously provides exceptional passive daytime radiative cooling and enhanced fire safety. The material is fabricated via a two-stage fabrication procedure: delignifying natural wood so as to construct a porous framework with inherent light-scattering properties, followed by infiltrating it with a functional mixture of polyvinyl alcohol (PVA), ammonium polyphosphate (APP), and silica (SiO₂) microspheres thereby forming a structurally integrated aerogel-mimicking structure within the wood's microchannels. The final composite demonstrates outstanding optical characteristics, achieving 89% solar reflectance and 97% thermal emissivity within the atmospheric transmission window (spanning 8–13 μm). These properties enable sub-ambient cooling, achieving a maximum 15.6 °C temperature reduction relative to pristine natural wood under direct solar irradiation. In terms of fire safety, the composite attains a UL-94 V-0 classification, demonstrating self-quenching properties and significantly reduced heat release rate during combustion. This multifunctionality arises from synergistic component contributions: the delignified wood provides a reflective and insulating base, SiO₂ microspheres enhance solar scattering, and the PVA-based matrix improves mid-infrared emission. The APP/PVA system acts as the primary flame-retardant by promoting char formation, while SiO₂ particles provide supplementary barrier effects. This research proposes a feasible and eco-friendly strategy for engineering high-performance construction materials that reduce cooling energy demands while improving fire safety, offering a promising pathway toward energy-efficient and safer built environments. • A novel wood-based composite integrates passive daytime radiative cooling (89% solar reflectance, 97% emissivity) and UL-94 V-0 flame retardancy. • Achieves a maximum 15.6 °C sub-ambient cooling under direct sunlight, outperforming natural wood significantly. • Delignified wood scaffold + PVA/APP/SiO₂ aerogel enables synergistic light scattering, heat emission, and char formation. • Building energy simulations confirm ~7–9% cooling energy savings, especially effective in hot, sunny climates. • Sustainable fabrication strategy offers a practical pathway for energy-efficient, fire-safe building materials.