Sustainable building is putting the spotlight on local, high-tech wood
By: Reid Singer October 18, 2019
Photo by Brady Hummel
The Kendeda Building for Innovative Sustainable Design, in Atlanta, is as impressive as any spaceship. Located on the Georgia Tech campus, the structure is the largest academic building in the Southeast to be certified as a Living Building.
Upon completion, the exterior will have an array of over 900 photovoltaic panels and a fully functioning rooftop garden with an apiary and berry orchard. Inside, rainwater flows into a large cistern, which can be treated and used on-site, and water-cooled pipes, which are embedded in the floors, reducing the need for air conditioning. Taken together, these features will help the edifice generate about five percent more electricity than it needs.
But what's even more impressive is the construction itself, which relies heavily on wood. Columns and beams, made from glue-laminated timber (glulam), hold up 489 ceiling panels of nail-laminated timber (NLT), built using 25,000 linear feet of locally salvaged two-by-fours. While these elements give the interior a more organic look than, say, the offices at Cape Canavereal, the Kendeda Building nevertheless resembles a place where your great-great-grandchildren might go to school.
When I visited the building in July, it was late in the afternoon, and I was struck by how the high ceilings and tall windows let in pools of natural light. The columns and beams seemed to shimmer, and the hues of the wood felt innately soothing and warm. Next to the solid grays and blacks of construction, the gently-shifting shades of the grain made everything a little fresher and more inviting.
"It's awesome," said Jimmy Mitchell, lead project manager for Skanska construction. Standing in the atrium, Mitchell said he hoped the Kendeda Building would give other firms ideas about what they can accomplish with the mass timber framing style. "Designers, structural engineers and owners can look at this and say, 'For my next commercial application, I want to consider wood structure.'"
The Kendeda Building during construction. In the foreground are panels of nail-laminated timber (NLT). There were a total of 489 panels made from salvaged two-by-fours by the building. (Photo by: Brady Hummel)
Light, Strong and Resilient
As a category, mass timber describes engineered products that have been made by laminating or compressing multiple layers of wood into single, solid panels. Glulam and NLT have many advocates, though firms also seek out dowel-laminated timber (DLT). Other options include cross-laminated timber (CLT), in which layers of dimension lumber are secured together at right angles, and structural composite lumber (SCL), manufactured from blocks of dried and graded veneers, strands or flakes.
The refining process is fairly simple, but mass timber products are light, strong and resilient, with a commanding load-bearing capacity and a superior resistance to fire and heat. And while these properties would be familiar to anyone who's seen a tall pine sway in the wind without snapping - or watched a campfire log take hours to burn - mass timber is a uniquely 21st-century technique. The International Code Council (ICC) recently settled on changes that will permit it for the design of taller buildings, and only a few structures in North America have put it to use.
Whether it's applied to a single-family lodge or a giant airport terminal, Mitchell believes mass timber holds unparalleled advantages over steel or concrete. Wood is a natural and renewable carbon sink, and harvesting it leaves a far lower environmental impact than mining. Compared to conventional materials, mass timber can be cheaper to build with and easier to install, which speeds up construction times and drives down labor costs. When it's applied to new buildings in growing cities, it opens up new revenue streams from forests in more rural communities. Given all of these benefits, Mitchell says he's not surprised by the new embrace of mass timber by his peers.
Advocacy is Changing Minds
Until recently, access to mass timber was fairly limited, especially in the Southeast, where only one facility manufactures it. The Long Hall, in Whitefish, Montana, is the first commercial building project in the United States constructed with CLT and was only completed in 2011. Even in Europe, where builders have been using mass timber since the 1990s - and where about four-fifths of the world's CLT is still made - it remains a niche product: only 680,000 cubic meters were produced in 2016, compared to 1.068 billion cubic meters of wood products consumed.
Mass timber is growing, however, thanks to years of advocacy among architects, construction material specialists and authorities in fire and safety. Bruce Lindsey, the South Atlanta regional director for WoodWorks, says the nonprofit has already devoted 40,000 hours of workshops and seminars to the subject, educating industry professionals about the material's sustainability, cost-effectiveness and resistance to harsh weather. Before tall wood buildings could be allowd into the 2021 International Building Code, the ICC convened the Tall Wood Building (TWB) Ad Hoc Committee in December 2015 and chartered it to conduct a long, detailed technical review of mass timber knowledge and building performance. The general public has needed convincing, too: wood, after all, is an excellent fuel source, with a role in some of the most destructive urban fires of the early 20th century. It had been banned from use in the construction of theaters and schools in cities around the country, but experts now say that mass timber can be safer - and tougher - than conventional materials.
"I'd rather be in a 10-story building out of wood than a two-story building out of unprotected steel," said Pat Layton, director of the Wood Utilization and Design Institute at Clemson University. "Wood is combustible, but it's extremely fire-resistant, and it burns at a very predictable rate."
Layton pointed out that wood chars uniformly at about one-and-a-quarter inches per hour. As the exterior burns, the resulting carbon build-up acts as a natural insulator, forming a seal that blocks the underlying tissue from oxidizing. As a result, timber can burn slowly and consistently, retaining its integrity for hours, rather than falling apart in sudden bursts. By contrast, moisture trapped in concrete can pressurize and expand at high temperatures, causing layers to violently break off, and the strength in metals can quickly dissipate at around 1,000 degrees Celsius. While every material has inherent risks, Layton believes the risks of timber are fairly straightforward to manage - especially when used with effective sprinkler systems, heat-resistant gypsum board and sensible fire exits that are easy to reach.
"You have to take care of the envelope," she said. "Sewers leak. Roofs leak. Steel rusts. Over time, you'll even see cement flaking. Any building - steel, concrete or wood - you have to take of it. But if you take care of it, it's going to be fine."
When talking about wood's performance in hurricanes, earthquakes and other disasters, Layton described TNT blast tests of mass timber initiated by the U.S. Army in 2018. These results were promising and led to the use of CLT for four- or five-story structures that house soldiers and their families, many of them featuring staircases and elevator shafts. She was also adamant about the role that mass timber construction plays in stimulating the local economies in the Southeast, a view shared by leaders in the forestry profession, including Georgia Forestry Association President and CEO Andres Villegas.
"Products like CLT or glulam represent a new use of lumber," he said. "We have such a thriving building and construction community in Atlanta, Savannah, Macon, Athens and Valdosta, and we're projected to add five million people over the next 20 years. As our state continues to add population, some of us are going to be living in buildings that are made from mass timber that's cut in Georgia and from trees that are grown in Georgia."
"A Sustainable Way to Build"
What this means for Georgia's forest landowners is signaled, in part, by the opening of a new mass timber facility in Dothan, Alabama. Operated by the Flordia-based International Beams, the 227,000-square-foot factory now employs over 50 people and is the first mass timber facility to trade primarily in Southern yellow pine. Working with vendors like Rex Lumber, Interfor and WestRock, the site produces CLT for firms like Gainsborough Architects and Cooper Carry.
"It just seems like a no-brainer to us," Simon Siegert, architectural designer for International Beams, said about the local market for CLT. "It's a sustainable ways to build, and it's a reasonable way to build for future generations."
Risher Willard, utilization chief for the Georgia Forestry Commission, said that the market for mass timber would help forest landowners derive the maximum benefit from their property.
"The Southeast is one of the largest wood baskets in the entire world," he said. "In Georgia, we're growing 41 percent more wood per year than we're using, and we need more outlets for wood products to utilize all of that excess supply. Any time you create more demand for wood products, it all comes back to the timber owner."
In June, Willard gave a presentation on the forest industry at the Georgia Environmental Health Association's annual education conference. He emphasizes the need to keep the public informed while restraining some of the hype about mass timber as a commodity - at least in the short term.
"CLT is going to be a slow-growth industry here in the U.S.," he predicted. "A lot of people are going gaga over this, like it's going to double the price that landowners get for their wood, but it's not going to have any effect on the average timber sale in Georgia for a long time. As more plants get built and more is used for these products, it's only going to help in that regard. But it's not going to be overnight."
Construction, like forestry, is almost always a long-term endeavor, requiring a firm understanding of how communities interact and adapt to change. While the payout is measured in decades - rather than in months or years - many architects believe that, with enough time and patience, the market for mass timber can help to connect city-based issues, like affordable housing, to the agricultural issues affecting less populous parts of the state.
"Timber is a product that brings the two Georgias together," says Bill de St. Aubin, CEO of the Sizemore Group, a firm based in Atlanta. "But before that can happen, the incentive is going to need to be there. Architecture is a big investment, and so you have to educate the bank, the insurance company and everyone else in the process. It's not like computer technology. It's something that's going to be around for a long time."
Inside T3 West Midtown, Hines Interests Limited Partnership's new 205,000-square-foot development in Atlanta's Atlantic Station. (Photo Courtesy of Hines Interests Limited Partnership)
Potential for Lower Emissions
Like other design professionals, de St. Aubin was particularly encouraged by the role that mass timber could play in addressing climate change. Living trees are prized for their ability to absorb carbon dioxide through photosynthesis, and harvested timber can store carbon indefinitely. In theory, harvesting wood from local, responsibly-managed forests can have much lower emissions than manufacturing steel or concrete.
At the Kendeda Building, Jimmy Mitchell said this was one of the main reasons mass timber was involved in the Georgia Tech project. There's just as much interests, however, among for-profit companies. Hines Interests Limited Partnership, a global real estate investment firm, sought out glulam and DLT to construct the frame and decking of T3 West Midtown, a 205,000-square-foot development in Atlanta. Because these components were fabricated off-site, they could be unloaded and installed with just a handful of people, leading to enormous savings in time and staffing resources. It also looks fantastic; the glulam components are as smooth and elegant as any material, with friendly earth tones that are soothing to the eyes.
"I think our customers really appreciate the story of wood," John Heagy, a senior managing director at Hines, said during a tour of the site. Even for commercial projects, he said people were drawn to the sustainability and aesthetics of mass timber. And the company took pride in the ecological impact: by using mass timber instead of metal and concrete, the structure will store 3,600 metrics tons of carbon dioxide and avoid 14,000 metric tons of emissions. This can be easy to overlook, since the building has a rustic wood core but is covered on the outside with dark zinc panels. Like the Kendeda Building, the modern and rustic effects are in perfect harmony.
"The exterior was designed to look like steel, but all of that is supported by wood," Heagy said. "This is a beautiful new building, with an old soul. And from a technology standpoint, it's top notch."
Reid Singer is a journalist based in Atlanta. He has written for Smithsonian, Outside, and The New Yorker.
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