Energy efficiency and carbon emission reduction of fly ash vacuum insulation boards: A coupled thermal modeling and lifecycle assessment

This study develops a fly ash-based composite insulation (FAHM-MF) to balance building performance and carbon reduction. It quantifies the impact of fiber volume fraction ( V fibre ) and vacuum conditions on pore structure parameters. Increasing V fibre reduces porosity ( φ ), fractal dimension ( D ), and regularizes pore structure, but lowers connectivity ( C conn ), affecting thermal conductivity ( λ ). Vacuum conditions enhance λ through low φ . The pore structure complexity coefficient ( k 2 ) is the most sensitive parameter to λ (sensitivity 79.28 %), with ±2SE fluctuations resulting in a ±8.2 % change. Sensitivities of the vacuum correction coefficient ( k 3 ) and fiber reinforcement factor ( β ) are lower at ±3 % and ±1.5 %, respectively. Lifecycle assessment shows FAHM-MF buildings reduce carbon emissions by 10.2 % (464.85 tons CO 2 ) compared to EPS. Sensitivity analysis further reveals that grid emission factors (sensitivity 0.96) cause ΔCO 2 fluctuations of ±28.75 % with ±30 % variation, and reduce the emission-reduction potential in coal-powered regions by more than 20 %. Extending building lifespan to 60 years improves ΔCO 2 by 17.7 %. This framework optimizes the use of building materials and supports sustainable development.