Impact of Silica Aerogel on Thermal Conductivity of Flame-Retardant Polystyrene Foam Cement Insulation for Exterior Walls

Improving building insulation materials is essential for reducing energy consumption and achieving carbon neutrality goals. This study investigates the effect of silica aerogel incorporation on the thermal conductivity and microstructure of flame-retardant polystyrene foam-cement composite insulation boards. Composite samples with different aerogel mass fractions were prepared, and their thermal conductivity was measured using a steady-state method, while microscopic characterization was conducted to reveal the heat-transfer mechanisms. The results show that increasing the aerogel mass fraction from 0.79% to 13.14% significantly reduces the thermal conductivity from 0.062 to 0.0465 W/(m·K), with an inflection point occurring at around 3%, beyond which the rate of decrease slows. The microstructural analysis confirms that aerogel addition introduces abundant nanoscale pores, reduces solid-phase heat conduction paths, and enhances the overall insulation effect. These findings demonstrate that an appropriate level of silica aerogel incorporation can effectively improve the thermal insulation performance of composite boards, providing a promising approach for developing high-efficiency building insulation materials.