The AEC industry recently has a newfound appreciation for wood and its applications in tall and mass timber construction. But the material's relatively lightweight and carbon-storing capacities are also inspiring innovators and scientists to experiment with new uses and manipulations. From readily available commercial products to highly modified materials, ARCHITECT is highlighting inventive examples of wood products and technologies below.
For building interiors, Milan-based Wood-Skin makes Fold Panels, a multidimensional system of triangulated wood-clad modules designed for vertical and horizontal applications such as feature walls, ceilings, and railings. Shipped flat, the 3D panels are structurally supported by an aluminum frame and come with a variety of surface options, including sound-absorbing felt and cork. The company also offers Mesh Sheets, a similar product that offers a wider variety of geometric patterns and surface materials. Subdivided into smaller, self-similar units, Mesh Sheets are somewhere between rigid panels and pliable textiles. According to the manufacturer, they allow “the construction of architectural membranes with the same functional properties and look-and-feel of ‘macro-tissues.’”
San Francisco-based Smith & Fong (also branded as Plyboo) offers decorative wall panels called Fractal. This product's triangular modules are dimensionally flat, yet impart visual interest via routed groove patterns in parallel lines. The 24 inch-by-24 inch-by-34 inch, 3/4 inch-thick isosceles triangles are made of Moso bamboo and come in varying colors and scales of line patterns. The modules can be oriented to produce optical illusions of depth and movement. Smith & Fong’s website includes a Fractal design tool that enables designers to simulate custom patterns in various room configurations.
Requiring a higher level of processing, wood is combined with other materials to create novel hybrids. Suffolk, U.K.–based Lignacite manufactures concrete masonry units consisting of recycled wood shavings, other waste materials, sand, and gravel. The company reports that its Carbon Buster block is carbon negative, sequestering more carbon dioxide than what its production emits. In addition to carbon-rich wood shavings, the block consists of Carbon8 pellets made from a carbon dioxide–storing combination of cement, sand, and water. Based on data from an Inventory of Carbon and Energy conducted at the University of Bath, the Lignacite masonry unit compares quite favorably to typical concrete masonry units or bricks.
Researchers at the University of British Columbia (UBC) have also made a wood-based concrete. Rather than creating masonry units, the scientists have fashioned non-structural panels intended as replacements for wall panels, countertops, or flooring. The UBC wood comes from local trees ravaged by the mountain pine beetle (MPB). “Normally, cement repels organic materials, such as wood,” said Sorin Pasca, an ecosystem science and management master's student working on the project. “But for some reason, cement sticks to lodgepole pine and this compatibility is even stronger when the tree has been killed—or you could say, enhanced—by the mountain pine beetle.” Unlike Lignacite’s product, the MPB wood concrete uses wood chips instead of gravel as its aggregate. It may therefore be modified using typical woodworking tools, permits nailing without pre-drilling, and is water-resistant. The material also provides a path to commercializing MPB wood, which sawmill operators have struggled to process in conventional ways.
At the University of Maryland, engineers have developed a process to make wood 12 times stronger and 10 times tougher. According to Liangbing Hu, the materials science and engineering professor leading the research, the modified material “could be a competitor to steel or even titanium alloys, it is so strong and durable. It’s also comparable to carbon fiber, but much less expensive.” The method involves removal of lignin, wood’s intercellular glue, and subsequent compression under low heat. The resulting material is reduced to 20 percent of its original thickness, with its fibers now held together by strong hydrogen bonds.
In a UMD press release, Brown University professor Huajian Gao described the technology as “a highly promising route to the design of lightweight, high-performance structural materials, with tremendous potential for a broad range of applications where high strength, large toughness, and superior ballistic resistance are desired.” The researchers anticipate that the process will lead to the replacement of hardwoods in furniture and other applications with modified softwoods that grow more rapidly and are more widely available.
Scientists at the KTH Royal Institute of Technology in Stockholm have performed similar lignin-removal experiments on wood with other results. Rather than pursuing strength, they have achieved optical transparency. Lignin is also responsible for wood’s coloration, and once it is removed, the material becomes white. To amplify the substance’s light transmission capabilities, Wallenberg Wood Science Center professor Lars Berglund and his team impregnated the porous material with a transparent polymer. The result is a thin substrate reminiscent of Plexiglas, which the researchers believe could be a sustainable alternative to window glazing and the glass surface of photovoltaic panels. "Transparent wood is a good material for solar cells, since it's a low-cost, readily available, and renewable resource,” Berglund said in the release. “No one has previously considered the possibility of creating larger transparent structures for use as solar cells and in buildings.”
But Be Wary
Despite the many impressive innovations in wood materials, cautions remain. We must improve the monitoring of wood’s chain of custody to avoid deforestation, biodiversity loss, and other ecological impairments that can result from the mismanagement of forests. Novel hybrids like wood concrete, particularly when made with waste wood fibers, are based on compelling arguments for material sustainability. Yet one should always be careful when creating composites in which the original ingredients cannot be easily extracted for recycling purposes—especially when the components come from both biological and technical resources, a phenomenon "Cradle to Cradle: Remaking the Way We Make Things" (North Point Press, 2002) authors William McDonough and Michael Braungart call “Frankenstein products.” For example, Lignin is a rich carbon sink, with an energy content equivalent to that of coal, but manipulation of the cellular can affect this carbon storage potential.
In the context of responsible environmental practices, wood brings newfound capacities that promise many positive transformations in the current and future built environment. As the AEC industry becomes increasingly carbon-aware, wood building products could motivate a sea change, supplanting many nonrenewable, energy-intensive substances with renewable, carbon-storing biomass.