Architects and developers are thinking differently about the environmental impact of materials they specify. They are shifting from linear to circular design principles so that buildings, like biological processes themselves, have a more regenerative life cycle.
Project teams are now considering how to prolong durability, reduce waste, and assess the sustainability of materials throughout the entire project lifecycle. By specifying bio-based and naturally renewable materials like wood, AEC professionals can extend the service life of their buildings in support of a circular economy.
The volume of material operating in the U.S. construction industry is immense: the World Resources Institute estimates that 80% of all materials and minerals in circulation in the American economy are consumed by the construction industry.
The built environment is the world’s largest consumer of raw materials by sector and produces significant construction and demolition (C&D) waste. In 2018 alone, the U.S. generated 600 million tons of C&D debris— the equivalent weight of more than 30 million school buses and over twice the amount of municipal solid waste picked up from homes and businesses.
As the data reveals, building materials have historically followed a ‘take, make, dispose’ linear model of consumption, where resources are extracted for product manufacture and products are disposed of at the end of their life.
But with building materials accounting for 39% of global GHG emissions, there is a growing imperative for AEC professionals to consider product end-of-life in their specification decisions. This includes a shift to a circular economy and choosing building materials that are naturally renewable, and/or can be reused or remanufactured at the end of their use.
Circular Economy (CE) is “a regenerative system in which resource input and waste, emission, and energy leakage are minimised by slowing, closing, and narrowing material and energy loops. This can be achieved through long-lasting design, maintenance, repair, reuse, remanufacturing, refurbishing, and recycling”.
Wood products are naturally renewable, reusable, biodegradable, and can be sustainably harvested. As a structural building material, wood is also well-suited to reconfiguration, reuse, and recovery. Considering the embodied energy represented by C&D waste, and the implications of continued materials disposal, wood’s adaptability makes it an effective building material for a low-carbon future.
Keep reading to learn about four ways wood can support a circular economy.
Wood is a resilient material that can provide decades, even centuries, of service when properly maintained. Ancient wood buildings continue to stand including 8th century Japanese temples, 11th century Norwegian stave churches, and the many medieval post-and-beam structures of England and Europe.
In surveys of building age, wood buildings consistently have the longest lifespans. This demonstrates that wood structural systems can be maintained to achieve long building life spans. Horyuji, a Buddhist temple in Japan, is currently the world’s oldest wood building at more than 1,400 years of age.
One contemporary example of wood’s long lasting durability is Butler Square—built over one hundred years ago as a warehouse for the Butler Brothers Company, this nine-story historic tall timber building in Minneapolis, Minnesota demonstrates that wood withstands the test of time.
While originally designed to serve as a warehouse, the building has gone on to provide a range of uses. When truck transportation replaced rail in the region, the building’s urban location rendered it inefficient as a warehouse. In 1972, a renovation and adaptive reuse added a central atrium to the eastern half of the building drawing natural light into the building, making it more marketable as retail and office space. Smaller renovations and adaptations have continued over the years.
Today, the building is considered an architectural icon and continues to attract a wide range of tenants: “The great thing about Butler is we have a wide variety of tenants, from attorneys to advertising and architectural firms to computer consultants,” says Sonja Breyfogle, leasing associate with United Properties. “It appeals to a younger employee base as well as to tenants looking for more luxury type-A space.”
Butler Square has become the first 100+-year-old, multi-tenant commercial building in the world to win LEED EB O&M certification.”
Building with wood can help reduce construction waste through factory-built prefabrication which can optimize assembly and streamline onsite erection.
“Renewable materials such as wood have been identified as an ideal construction material—especially when incorporating innovative mass timber products such as CLT and glulam, design methods and processes like BIM and DfMA, tools for visualization such as VDC, and tools for manufacturing such as CNC,” writes architect Eduardo Souza.
The use of these technologies can complement the environmental benefits of prefabricated timber systems, resulting in higher productivity, reduced amount of change orders and issues during construction, higher quality, and reduced waste.
Wood waste can be reduced when the design team engages the manufacturers early in the design process and incorporates the manufacturer’s standard product sizes efficiently in their designs.
One company with a commitment to waste reduction has turned its focus to the use of timber framed systems. DIRTT (Doing It Right This Time) is an interior construction company that delivers fully customized interior environments for flexible office designs, healthcare facilities, educational environments, retail, and more.
DIRTT was the first interior construction provider to complete a life cycle assessment and environmental product declaration.
DIRTT’s product line includes modular timber frame options including mezzanines and second floors, interior canopies, and timber accents for workstations and reading nooks. Their products and business model are rooted in efficiency and circularity.
“As a custom manufacturer, we recognize that we will always have some waste. However, we work diligently to reduce waste production and responsibly manage what we do generate. We aim to use packaging materials that are reusable or recyclable. We have extensive recycling programs throughout our facilities to divert materials from the landfill.”
Company designers and installers routinely re-visit customer spaces to reconfigure, upscale, or repurpose their products. DIRTT’s modular system can be modified onsite for new occupants or a change in the existing occupant’s needs, further reducing construction waste.
Wood is a material well-suited to reuse, whether through the adaptive reuse of an existing structure or through deconstruction and disassembly.
In particular, long-standing heavy timber beams in existing buildings and structures are sought after for its durability and strength, along with its aesthetic beauty and historic significance.
Due to its rising value, a growing number of companies, such as Unbuilders, specialize in the deconstruction and reuse of this type of timber.
It has been said that the greenest buildings are the ones that already exist. Adaptive reuse is the process of redeveloping structurally sound older buildings for economically viable modern uses, infusing new life into a historic shell. Adaptive reuse can allow a project to significantly reduce its embodied carbon as well as the volume of materials sent to landfill through construction.
A compelling example of such an adaptive reuse is Milwaukee’s first mass timber building, Timber Lofts. The project combines a 130-year-old warehouse renovation with new mass timber construction in an adjacent parcel.
The idea from the onset was to harmonize the existing building with new construction.”
In the renovation, individual boards were meticulously deconstructed from the warehouse, stacked, and set aside for cleaning and sandblasting to remove paint, exposing the wood’s maple grain.
After subflooring and sound control materials were added, the original wood floor was reinstalled. In addition to the reclaimed wood floor, the original arched window openings, rolling fire doors, and exposed heavy timber frame, including wood joist rafters, also were preserved.
The project shows how reclaimed wood and new mass timber construction can come together—full circle—reducing waste while delivering a thoroughly modern building with historic charm.
Wood is also well suited to deconstruction and disassembly when a building’s original service life ends. Modern wood buildings can be designed from modular components that can be refurbished as required or remanufactured into new products. For instance, structural elements might be disassembled and set into new configurations over time or wood floors might be deconstructed and used for paneling.
The aim of DfDA is the design of buildings to facilitate future change and the eventual dismantlement (in part or whole) for recovery of systems, components, and materials. DfDA offers flexibility, convertibility, addition, and subtraction of whole-buildings.
We say ‘design for long life, loose fit’. By designing for long life and end-of-life scenarios responsibly, wood is uniquely suited to disassemble. By using loose bolts, pins, and screws, and avoiding welding and friction-tight bolts, wood is easy to take apart.
StructureCraft, an engineer-led fabricator of innovative timber structures, has set a new standard in industrial wood building design.
The company’s 50,000-square-foot manufacturing facility showcases new levels of engineering efficiency for industrial buildings, combining a variety of mass timber and engineered wood products, including dowel-laminated timber (DLT), laminated strand lumber (LSL), nail-laminated timber (NLT), and glued-laminated timber (glulam).
To demonstrate the flexibility of mass timber in industrial buildings, StructureCraft designed the entire building as a demountable structure, providing flexibility to expand or move the facility entirely to a new location.
The building was planned according to principles of design for deconstruction with the key features being reuse of existing structure in proposal, use of screwed steel connectors, and collaboration with contractor.
“We believe there’s a more efficient and effective way to construct the industrial buildings of the future using this method,” the company writes.
“The new facility was designed to explore what could be possible using wood for a simple industrial building with a tight budget. That exploration, while not simple during the design phase, has created a prototype which proves that modern industrial buildings may be created cost-effectively, and attractively, using wood.”
When materials reuse is not possible, you can recycle bio-based materials components like wood into other products including particle board and wood pellets or chips.
Energy can also be recovered from wood products in the form of biomass. Upon final disposal, bio-based materials can serve as fuel for microorganisms like termites and fungi, eventually degrading into biological nutrients.
There is a growing imperative in the AEC industry to shift to circular design principles to help reduce carbon emissions and excess material consumption and waste. Naturally renewable materials like wood, can play an important role in making this transition a reality.
The building and construction sector is massive and the pathway to a more circular economy can appear daunting and complex. All that said, as architect Clare Miflin —a key author of the Zero Waste Design Guidelines—succinctly reminds us, the basic principle remains simple: “Build less. For more people. Design circular.”
