Harvard group turns waste wool into retrofit cladding tiles

Harvard University's Grinham Research Group has developed an insulating exterior cladding tile made from waste wool, and presented it at this year's Oslo Architecture Triennale.

The research group showcased the tiles in an installation named Upcycling Wool Ecologies, mounted on a timber frame inside Oslo's Sofienberg Church as part of the triennale's main exhibition, which runs from 17 September to 1 October.

The group identified wool's insulative, fire-resistant and antibacterial properties and set out to rescue the fibre from disposal as a residual material in the agricultural and textile industries. It also aimed to develop a material that facilitates building reuse.

The solution is a multi-layer tile applied to the exterior of buildings, avoiding the costly work of digging into a wall to upgrade its insulation. The tiles combine a low-density back panel that acts as an insulating board with a denser outer panel that provides greater durability and weather resistance.

"We need pluralistic solutions that reflect the complexity of nature," Grinham Research Group founder Jonathan Grinham told Dezeen.

"Architecture can actively design these new industrial ecologies that retain the value of materials, skilled labour, and existing industries while creating scalable retrofit solutions," he continued.

"By transforming waste wool into durable exterior cladding, biogenic carbon captured through grass, sheep, and wool can be retained in the built environment, while the same material improves the performance and extends the useful life of existing buildings."

The production process starts with an alkaline treatment that partially breaks down the wool's keratin proteins. A mechanical process then separates the material into a liquid. Citric acid is added and, when heated with the wool-derived keratin, binds residual and unprocessed wool fibres into a rigid composite without the need for a petrochemical resin.

According to the group, around 1.95 billion kilograms of raw wool are produced each year, with approximately 60 per cent used for wool clothing manufacturing. Unused wool is typically stockpiled, burned or buried.

"The decline of domestic textile manufacturing, competition from synthetics, and selective grading have left enormous quantities of wool without a viable market," said Grinham.

"Wool has lost its economic value, but not its material properties," he continued. "We're developing new chemistries that transform this overlooked natural polymer into a useful biocomposite for building insulation and cladding."

For the triennale installation, the group sourced preconsumer waste wool from the American Woolen Company in Connecticut. It used a mixture of naturally coloured and dyed fibres, which produced the variations in tile colours.

The tiles on show featured a fluted surface design, though the material could be pressed into different shapes and designs.

The project joins a growing field of bio-based material research aimed at the retrofit market, and positions waste wool — a fibre with no viable market in the eyes of the textile industry — as a feedstock for extending the useful life of existing buildings.