Swapping Straw and Sheep’s Wool for Concrete and Steel

This article is reprinted with permission from Bloomberg Design Edition, where it originally appeared. It was first published on July 26, 2026.

When a colleague alerted me to the “Bio-Based Materials Petting Zoo and Happy Hour,” one of several interactive events during Boston Climate Week this summer, there was no way I wasn’t going. For a journalist who often chronicles the nerdy aspects of architecture, newfangled sustainable building materials equals pure catnip.

The show-and-tell, held at Boston Building Resources, a local nonprofit that collects and distributes salvaged construction materials, didn’t disappoint. Curator Sara Kudra offered a full roster of alternative building blocks for the built environment, including hemp, cork, straw, flax and bamboo. We passed around samples of rice husk wall panels, cinder blocks bound with wood fiber, insulation made from sheep’s wool, and acoustic tiles composed of reconstituted crushed glass.

And while the materials were conjured using cutting-edge technology, with futuristic names like Craste, Nexcem, and Glavel, the precedent for more nature-based building is firmly rooted in the past, Kudra said. Bricks of compressed earth, for example, offer a modern version of the vernacular mud hut. “Humanity has known about a lot of this stuff for thousands of years,” she observed as she passed around a test tube of an algae-based cement additive.

Alternatives to conventional building materials have been gaining attention in recent years, from mass timber to green cement. Today the roster of funky ingredients is expanding rapidly, promising healthier interiors, lower costs, better energy efficiency and longer-lasting buildings that require less maintenance. It’s all of a piece in the trend of more sustainable architecture, with its aspirations of a circular economy, reuse and retrofit, and a transition to a postcarbon future.

Can all of this stuff really replace brick, steel and concrete? The idea of sheared sheep’s wool substituting for fiberglass insulation—or importing cork from Portugal for walls and floors—suggests it might be hard for these materials to break out of boutique usage and scale up.

“Currently, scale in the building industry means that you have one manufacturing facility in Georgia that is basically producing all of the carpet tiles that are needed in North America,” says James Kitchin, director of the Abundant Futures Design Lab at the design firm MASS, cofounder of the Bio-Based Materials Collective, and contributor to The Bio- & Mineral-Based Materials Primer, a guide for contractors and design professionals. “The other form of scale is to have more of a dispersed network of manufacturing facilities—more localized supply chains that are more resilient.”

At a practical level, there’s lots of win-wins in more planet-friendly protocols. Farmers discard or burn tens of millions of tons of straw each year; instead, they could sell it to manufacturers of straw-bale structural insulated panels. Cost savings are achieved in the long run, on energy use, maintenance and durability over the life cycle of any building. Builders can also save on labor costs; prefabricated cross-laminated timber, as hardy as steel, is famously easy to work with, trimming construction timelines.

Sustainable building materials are also in many cases safer and less flammable than traditional materials. Compacted straw basically just chars rather than going full-on aflame, unlike the synthetic elements blamed for recent high-rise conflagrations around the world. The task is to convince lawmakers to overhaul government regulations and building codes that favor conventional methods and manufacturers—but that’s an uphill battle.

“There’s so many challenges around the entrenched system that we already have, around regulations, warranties and risk aversion,” Kitchin said.

Change is unwelcome in many quarters. Residents in Moreau, New York, rose up to fight a proposed plant that would have turned sewage sludge into biochar, a charcoal-like substance that can be used as a carbon-storing additive. Other places are revising rules and incentives: Seattle established a program to promote mass timber and super-insulated “passive house” techniques in areas zoned for more dense, multistory housing construction.

The evolution of building materials has gone hand-in-hand with changes in design. The earliest human settlements used stone, wood, packed earth and other materials that were handy and close by; builders in ancient Rome combined the invention of concrete with clever engineering to create aqueducts and temples. Wood and brick were standard until the Industrial Revolution brought iron and steel, paving the way for the first skyscrapers. Brutalist architects like Le Corbusier and Paul Rudolph used structural concrete in new ways, and Frank Gehry’s wavy metallic forms were facilitated by aerospace software.

The first sun-dried mud bricks can be traced to Syria more than 7,000 years ago. Today innovators have come up with a porous terracotta version that can absorb water and cool down outside spaces that are subject to extreme heat. All it took was some smart people to take a fresh look at this most basic element of building, so familiar after millennia of use. The ubiquitous cinder block shouldn’t be far behind.

Anthony Flint is a senior fellow at the Lincoln Institute of Land Policy, host of the Land Matters podcast, and a contributing editor to Land Lines magazine.

Lead image: Straw bales fill the wooden framing of a house under construction. Credit: anandoart via Getty Images.