This study investigates the valorization of post-consumer and post-industrial recycled cotton fibers from textile waste into porous fiber-based insulation composites using a low-temperature cold-pressing process and a water-borne hybrid binder based on polyvinyl acetate (PVAc) and modified cornstarch. Insulation boards were produced with target densities ranging from 300 to 340 kg·m⁻³, achieved by systematically adjusting the percentage weight fractions of recycled cotton fibers and binder components. The influence of board density on microstructure, inter-fiber bonding, and structure–property relationships was evaluated. The resulting boards exhibited thermal conductivity values between 0.0710 and 0.0739 W·m⁻¹·K⁻¹. Compressive strength measured at 10% relative deformation of the specimen thickness ranged from 46 to 162 kPa, while internal bond strength varied between 2 and 6 kPa. Water absorption decreased by approximately 18% with increasing density, indicating improved binder distribution and reduced open porosity. The PVAc–starch binder system enabled effective inter-fiber bonding without formaldehyde-based resins or energy-intensive curing, supporting a low-temperature and circular processing concept for textile waste valorization. Overall, the results demonstrate that recycled cotton fibers represent a viable feedstock for porous insulation composites combining balanced thermal, mechanical, and moisture-related performance with potentially reduced environmental impact.

This study investigates the valorization of post-consumer and post-industrial recycled cotton fibers from textile waste into porous fiber-based insulation composites using a lowenergy cold-pressing process and a water-borne hybrid binder based on polyvinyl acetate (PVAc) and modified cornstarch. Insulation boards were produced with target densities ranging from 300 to 340 kg·m⁻³, achieved by systematically adjusting the percentage weight fractions of recycled cotton fibers and binder components. The influence of board density on microstructure, inter-fiber bonding, and structure-property relationships was evaluated. The resulting boards exhibited thermal conductivity values between 0.0710 and 0.0739 W·m⁻¹·K⁻¹. Compressive strength measured at 10% relative deformation of the specimen thickness ranged from 46 to 162 kPa, while internal bond strength varied between 2 and 6 kPa. Water absorption decreased by approximately 18% with increasing density, indicating improved binder distribution and reduced open porosity. The PVAc–starch binder system enabled effective inter-fiber bonding without formaldehyde-based resins or energy-intensive curing, supporting a low-energy and circular processing concept for textile waste valorization. Overall, the results demonstrate that recycled cotton fibers represent a viable feedstock for porous insulation composites combining balanced thermal, mechanical, and moisture-related performance with reduced environmental impact.

Summer overheating is an escalating challenge for lightweight timber constructions, which inherently lack the thermal mass of traditional masonry. This study investigates the thermo-physical properties of a mycelium-based biocomposite (MBB) insulation produced from industrial wood waste, with particular focus on volumetric heat capacity (C_v). The C_v and thermal conductivity (λ) of MBB were experimentally measured and benchmarked against seven reference insulation materials spanning bio-based, mineral, and petroleum-derived categories, with results visualized on an Ashby diagram. The areal heat capacity (κ) of nine representative wall assemblies was theoretically calculated per EN ISO 13786. Even though the MBB achieved the highest thermal conductivity (λ = 0.0641 ± 0.0024 W·m⁻¹·K⁻¹) among the tested insulation materials, it offers 4.7 times higher C_v than EPS. Analytical modeling indicates a thermal phase shift of 8.2 h for a 185 mm layer, compared to 4.6 h for EPS. The softwood timber + MBB wall assembly achieved an areal heat capacity approaching the lower boundary of traditional masonry performance. These findings demonstrate MBB’s potential as a bio-based, waste-derived insulation for significantly enhancing the thermal inertia of lightweight timber buildings and mitigating summer overheating risk.

Recycled cotton fibers offer a promising route for sustainable thermal insulation, but their flammability limits wider application. This study evaluated rigid recycled cotton insulation boards bonded with a polyvinyl acetate (PVAc)–starch system and modified with kraft lignin or aluminium trihydroxide (ATH) at dosages of 10 and 15 wt.%. Board density, thermal conductivity, volumetric heat capacity, thermal diffusivity, cone-calorimeter behavior, and ignitability under single-flame exposure were assessed. Thermal conductivity remained within a narrow range of 0.071–0.075 W·m⁻¹·K⁻¹, indicating that the basic insulation function was preserved despite formulation changes. Greater differences were observed in volumetric heat capacity and thermal diffusivity, particularly in lignin-modified boards at higher PVAc contents. Fire behavior was strongly formulation-dependent and showed no uniform dose-dependent response. The lowest peak heat release rate (pHRR) was obtained for the formulation containing 10 wt.% ATH and 20 wt.% PVAc, while the lowest total heat release (THR) was obtained for the formulation containing 10 wt.% ATH and 18 wt.% PVAc, reaching 170.31 kW·m⁻² and 62.30 MJ·m⁻², respectively. Lignin produced a less consistent effect on heat release. Under single-flame exposure, edge application was generally more critical than surface application, while ATH, particularly at 15 wt.%, provided the most consistent reduction in ignition and early flame spread. Overall, ATH was the more promising fire-modifying additive, although further formulation optimization and formal reaction-to-fire classification are required.