Waste Wool Becomes Biobased Cladding and Insulation for Building Retrofits

Researchers at Harvard University have developed wool biocomposite panels that use discarded textile fibres as both reinforcement and binder. The project, Upscaling Wool Ecologies, explores how this underused resource could provide cladding and insulation for existing buildings while connecting wool processing with established manufacturing infrastructure.

Developed by the Grinham Research Group in collaboration with Harvard’s Aizenberg Group, the material combines wool-derived keratin with citric acid. This approach produces panels without a petrochemical resin binder.

Turning Textile Waste Into Building Materials

Global sheep wool production reaches approximately 1.95 billion kilograms annually, yet medium- and coarse-grade fibres often struggle to find buyers. Unsold wool may end up stockpiled, burned or buried, despite retaining useful material properties.

The project uses pre-consumer waste from the American Woolen Company in Connecticut. These fibres have already undergone cleaning and textile processing. Their natural and dyed colours remain visible in the finished panels.

Keratin, the protein that makes up around 90–95% of wool fibre, provides the basis for the binding system. Alkaline treatment and mechanical processing partially break down the fibres to create a keratin-rich dispersion. Citric acid then helps form chemical links between the protein chains during heating, creating a matrix that binds the remaining wool fibres.

Different Densities for Different Functions

Adjusting fibre refinement, keratin content, citric acid concentration, pressure and temperature allows the researchers to tailor panel performance.

Dense formulations prioritise stiffness and moisture resistance. Reported results include a flexural modulus of approximately 1,906 MPa and water absorption of around 24% after 24 hours.

Lower-density formulations omit the final heat-pressing stage, retaining more air within the fibre network. The project reports thermal conductivity of approximately 0.045 W/m·K for these panels, comparable to expanded polystyrene insulation.

The Stock Tank, a prototype exhibited at the 2026 Oslo Architecture Triennale, combines 90 low-density panels for thermal insulation and sound absorption with 90 high-density exterior cladding panels. Fluting adds depth and stiffness to the outer surface, demonstrating a potential assembly for exterior building retrofits.

Scaling Through Existing Infrastructure

Working with North Carolina State University’s Pulp and Paper Pilot Plant, the team expanded processing from hundreds of grams to hundreds of kilograms.

Pulping machinery provides the agitation and fibre refinement needed for wool processing. Existing screening, dewatering, pressing and drying equipment could support further production, offering a route to scale through established facilities.

Understanding the Carbon Balance

The project’s life cycle assessment reports approximately 0.42 kg CO₂-equivalent per kilogram of panel material. Including stored biogenic carbon changes the reported balance to approximately −1.41 kg CO₂-equivalent.

These figures depend on assessment boundaries and how sheep-farming impacts are allocated to waste wool. Carbon storage lasts for the product’s service life, while any soil-carbon benefits from grazing depend on local conditions and management. The results therefore describe a specific production scenario rather than a universal carbon footprint for wool.

Source & photos: Grinham Research Group