Development and thermal optimization of cellulose-based insulation panels reinforced with cementitious industrial by-products

The growing demand for thermal insulation materials to improve building energy efficiency and indoor comfort has driven interest in sustainable alternatives derived from agro-industrial waste. In this study, six cellulose-based composite samples (C1–C6) were fabricated from recycled office paper with varying proportions of fly ash and Portland white cement (PWC) as additives. Physical properties and moisture absorption were assessed. Thermal properties were measured using a HotDisc TPS-500S system. A validated numerical model was simulated using ANSYS Fluent 2022, and the degree-day method was employed to estimate the annual energy cost based on the climatic conditions and energy charges in Delhi, India. An economic optimization approach was used, balancing both material and energy costs, and considering the Present Worth Factor to determine the optimum insulation thickness for each composition. Results showed that C1, with highest cellulose content, exhibited the lowest thermal conductivity (0.129 W/m·K) with high moisture absorption and lower durability. In contrast, binder-rich samples (C4–C6) showed enhanced structural durability and moisture resistance but higher thermal conductivity. The optimized thickness ranged from 35 mm to 95 mm, with C1 requiring the maximum thickness. Economic analysis revealed that while polyurethane foam remained the most cost-effective option, C1 presented a viable sustainable alternative at 41.71 % higher cost while offering significant environmental benefits. The study demonstrates the technical viability of cellulose-based composites in building insulation.