zippered wood

Forget Sustainable Construction—It’s Time for Sustainable Deconstruction

July 28, 2020

Recently, architecture professor Marc Swackhamer and his business partner Blair Satterfield, co-founders of HouMinn, won Architect magazine’s R+D Award for their clever invention with a transparent name—Zippered Wood. Swackhamer, Chair of the Architecture Department at CU Denver’s College of Architecture and Planning, isn’t exactly interested in sustainable building. He’s interested in sustainable un-building.

collage of zippered wood being created
Once milled, the two unique halves of Zippered Wood are paired together. Photos courtesy of University of British Columbia, HiLo Lab, University of Colorado Denver, LoDo Lab, and HouMinn Practice.

Architecture and Abandonment

“As we think more cyclically and sustainably, we need to consider the existing building stock in a more critical way,” Swackhamer said. Many commercial buildings have a life cycle of about 10 years (think about strip malls and office parks, for example), and yet most architects approach their work as if it’s permanent. “Architects never think about how their buildings come down,” Swackhamer said. “There is no incentive to think about decay.”

But there should be. According to Swackhamer, the global building industry contributes more than 50% of greenhouse gases, once you factor in construction, operation, demolition, and transportation. One solution may be in the building material itself. Instead of sending vast amounts of materials from demolished buildings into landfills, what if we could build with destruction in mind? “If the buildings we design can provide the nutrients for future growth of other built environments, then we’re thinking much more critically about what we do,” Swackhamer said.

Zippered Wood

With adaptive reuse in mind, Swackhamer, Satterfield, and their respective design labs, which are housed at the universities where they each teach—the University of Colorado Denver and the University of British Columbia (UBC)—invented zippered wood. The idea was to take the simple 2×4 and turn it into something complex and beautiful. 

Zippered Wood converts short lengths of waste 2x4s into long, curved posts and beams using only precise geometry. One segment of wood has a series of complex cuts that fits perfectly into the cut design on another piece. “The modified boards are ‘zipped’ together, forcing each other into predictably bent 2×4,” states the HiLo Lab at UBC, who has joined forces with CU Denver’s recently founded LoDo Lab. LoDo and HiLo are academic research labs where Swackhamer and Satterfield collaborate with students to create energy-efficient construction methods.

“We developed an algorithm where we can CNC-route into wood, and we can fashion that into any shape,” Swackhamer explains. CNC router stands for computer numerical control router, which is a computer-controlled machine that cuts wood (or other materials). One of the first projects to employ zippered wood was the Zippered Pavilion built on the University of British Columbia campus, which was completed in 2019 using repurposed timber. A complex construction of curved arches, the Zippered Pavilion highlights how lowly materials can be transformed into high art.

But Zippered Wood also has basic construction applications that save energy and reduce waste. “It could be used for thicker party walls or wider stud walls,” Swackhamer said. “We’ve calculated that by crisscrossing 2×4 zippered studs, instead of using standard 2x8s, 2x10s, or 2x12s, you could save as much as 300% in overall volume of wood used. Plus the wall, in such a scenario, is already hollow in the middle and doesn’t need to be bored out with drills and jigsaws after the wall has been erected, thus presenting labor savings. You wouldn’t see the zippered members in this case: they would be buried behind cladding and drywall, but the material and labor economies would be significant.”

zippered pavilion
The Zippered Pavilion is constructed of Zippered Wood technology, which uses short lengths of waste 2x4s.

Hypernatural, Geodesign, and Bioengineering

Swackhamer’s interest in sustainable design grew from research he conducted for his book Hypernatural: Architecture’s New Relationship with Nature, which he co-wrote with Blaine Brownell. Hypernatural provides an overview of projects by architects, designers, and scientists who work with nature through representation or engagement. While representative designs take inspiration from natural forms, “engagement involved direct interaction with natural substances—including living organisms—to create new designs,” the book states. Sometimes labeled geodesign or bioengineering, the engagement projects covered in Hypernatural include “bio bricks made by the calcifying processes of bacteria or biophotovoltaics that employ living algae to harness solar energy.”

detail and drawing of zippered pavilion
The Zippered Pavilion, which is a collaboration between the HiLo Lab, HouMinn, and LoDo Lab, uses Zippered Wood, which recently won Architect magazine’s R+D Award.

Swackhamer’s Zippered Wood is just one of many building products being created from abandoned materials. K-Briq, which was invented by Gabriela Medero, a professor of Geotechnical and Environmental Engineering at Scotland’s Heriot-Watt University, and engineer Sam Chapman, turns construction and demolition waste into bricks. The K-Briqs combine crushed bricks, gravel, sand, and plasterboard with water, a binder, and recycled pigments. The molded K-Briqs not only reuse construction waste. They also avoid problems associated with traditional bricks: clay mining, which ruins the land’s topsoil; and kiln baking, which contributes to climate change due to the fossil fuels used to heat ovens.

Elon Musk, whose Boring Company supplies infrastructure and tunnel construction services, announced in 2018 that he would be creating Lego-like bricks from discarded rock (see a video of a Boring Company engineer explaining the bricks). These materials illustrate that people are trying to change the construction industry in fundamental ways.

The Cows Are the Subcontractors

Other projects that Swackhamer admires go further than simply repurposing waste material. For example, Truffle House by Ensamble Studio in Spain was built by stacking hay bales and spraying self-reinforcing concrete on top. To finish the structure, “Herds of cows ate the hay from underneath,” Swackhamer said. “One of the biggest contributors to waste is formwork; the formwork was destroyed by the cows … The cows are the subcontractors,” he added.

The Truffle House turns construction into a symbiotic relationship with nature. The cows do what they want to do anyway—eat hay—and that simple act carves out the house structure. “I’m really interested in this idea that architecture may have a built-in obsolescence,” Swackhamer said, “and at a certain point it becomes subservient.” 

Video showing the building process of Truffle House, which involves formwork made from hay bales that gets eaten by cows.

Buildings as Life Cycles

What Swackhamer is interested in requires a paradigm shift in architecture. It means that architects don’t build one thing and then move on to the next. It asks architects to imagine what kind of life their buildings can create once they are no longer usable. 

“It’s definitely fair to say that furniture and interior designers have been thinking about this for a long time,” Swackhamer said. Now it’s time for architects and students “to think about materials that have a certain behavior or life cycle that allows them to be reused … to think about the next group of people and how they will use it.”