Sustainable Acoustic and Thermal Insulation from Natural and Recycled Fibers: Integrating Circular-Economy Principles into Building Material Science

This article presents a comprehensive, theory-driven examination of sustainable acoustic and thermal insulation materials derived from natural fibers, agricultural by-products, recycled textiles, and end-of-life household materials. The work synthesizes empirical results and conceptual frameworks from recent investigations into thermal degradation, moisture absorption, antibacterial behavior, acoustic absorption, and composite-reinforcement performance to produce an integrated perspective on how circular-economy principles can be operationalized in building envelopes and interior acoustic treatments. The abstracted narrative spans material selection rationale, physicochemical and microbiological durability, hygrothermal interactions, and acoustic performance mechanisms. It further situates passive insulation strategies within waste-management frameworks and regulatory contexts to propose practical pathways for large-scale adoption. Methodological discussion emphasizes reproducible, text-based experimental protocols and performance evaluation metrics widely reported in the literature. The results section offers descriptive analyses linking fiber morphology, surface chemistry modifications, and panel manufacturing parameters to measurable thermal and acoustic outcomes. The discussion critically examines trade-offs between thermal conductivity and sound absorption, the role of moisture and biodegradation in long-term performance, and the socio-technical barriers to mainstreaming low-cost bio-based insulators in vulnerable contexts. Limitations and future directions are articulated with explicit attention to lifecycle analysis, standardization needs, and scale-up considerations. This integrative article intends to inform material scientists, building engineers, policymakers, and circular-economy stakeholders seeking to advance sustainable insulation technologies.