Insulating buildings effectively is critical for energy conservation. Traditionally, insulation materials have been composed of synthetic polymers or mineral fibers. Recent research has explored the potential of biomass materials, leveraging their inherent insulative properties. To advance these capabilities, converting biomass into aerogel forms offers a promising approach due to their low density and thermal conductivity. This study focuses on producing coconut husk aerogel to assess its thermal insulation performance. The fabrication process involved blending sodium alginate, phytic acid, and coconut husk to create the aerogel. The influence of varying sodium alginate volumes on the fabrication of coconut husk aerogel was systematically investigated, given its crucial role in gelation. The produced aerogels were comprehensively characterized using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), Brunauer–Emmett–Teller specific surface area analysis (BET) and Fourier-transform infrared spectroscopy (FTIR). Thermal conductivity measurements were conducted to evaluate their insulation effectiveness. Results demonstrate that the coconut husk aerogel exhibits good insulation properties, characterized by significantly low thermal conductivity.