Posts tagged with "cross-laminated timber":

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IKD has pioneered hardwood cross-laminated timber

Thanks to a two-year, $250,000 Wood Innovations Grant from the United States Forest Service, and with further support from the National Hardwood Lumber Association, Indiana Hardwood Lumberman’s Association, and the Indiana Department of Natural Resources, IKD is currently working on an advancement that may completely change the cross-laminated timber (CLT) market. Currently, CLT is made primarily of softwoods, which have the advantage of being fast growing and inexpensive. IKD believes the future of CLT should also include hardwood, and now it just might. As a proof of concept, IKD has constructed a large installation, which stands as the first hardwood CLT structure in the United States. The project was built with an experimental CLT material made from low-value hardwood-sawn logs for Exhibit Columbus, the new architectural exhibition in the modernist mecca of Columbus, Indiana. A reference to the conversation pit in the Eero Saarinen–designed Miller House, the IKD’s Conversation Plinth is a multilevel occupiable installation in the plaza in front of the I.M. Pei–designed Cleo Rogers Memorial Library. The motivations behind using hardwood are two-fold. Currently, over 50 percent of the 80 million cubic feet of hardwood harvested in Indiana each year is used for low-value industrial products. By integrating this wood into the higher-value CLT, it raises the value of what is already Indiana’s largest cash crop. And from the perspective of designers and engineers, hardwood CLT provides the possibility of a more fire-resistant panel and a form-factor advantage. “We are currently exploring a number of applications that could have larger scale building applications,” IKD partner Yugon Kim said. “Since hardwood has superior mechanical properties, we believe we can achieve a panel that could be thinner to meet the same structural capacity of an equivalent softwood CLT panel.” The Conversation Plinth is not simply an exhibition piece for IKD. It is a test of the hardwood CLT the firm developed with SmartLam, the first CLT manufacturer in the United States. Over the months, the project will be subjected to the varied and sometimes-extreme weather of south-central Indiana, providing firsthand data that IKD and SmartLam can use to advance their research on the material. From the beating sun of late summer through the sleet, snow, and ice of winter, the project will be monitored for durability as well as aesthetic and structural changes. “We are closely observing the mixed-species panels and seeing how they react in the extreme temperature and moisture fluctuations so that we can continue to refine the species mix within the panel, the adhesion process, and the finish application and approach,” Kim explained. “It is really interesting to see how differently hardwood moves from softwood when the moisture content varies, and we are looking deeper at the fiber structures and unique characters of species themselves as well to create a superior CLT panel.” The project continues much of the timber research IKD has been doing, including its design for the Timber City at the National Building Museum in Washington, D.C., and work on timber modular waste units, a timber version of CMU made from timber waste that has won numerous awards. Resources Project Lead and Designer IKD CLT Fabrication SmartLam Timber Engineering Bensonwood Phase One Hardwood Testing Material Supplier Pike Lumber Company Phase Two Conversation Plinth Hardwood Material Supplier Koetter Woodworking General Contractor Taylor Brothers Construction Co. Softwood Material Supplier And Fabricator Sauter Timber
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Learning from Europe and Canada’s timber industry

If the steady stream of newly announced mass wood projects is any indication, mass timber building technologies are poised to take the American construction and design industries by storm over the next few years. As products like cross-laminated timber (CLT), nail-laminated timber (NLT), glue-laminated timber (glulam), and dowel-laminated timber (DLT) begin to make their way into widespread use, designers, engineers, and builders alike are searching for the best—and sometimes, most extreme—applications for mass timber technologies. But rather than reinvent the wheel, American designers can look to experienced mass timber designers in Europe and Canada for key lessons as they begin to test the limits of these materials in the United States. European and Canadian architects and researchers have long been at the forefront of mass timber design, starting with early experiments in the 1970s. By the 1990s, researchers like Julius K. Natterer at the Federal Institute of Technology in Lausanne, Switzerland, were developing initial CLT prototypes. Natterer’s work has been buttressed by that of many others, including research performed at the Norwegian Institute of Wood Technology under Thomas Orskaug and experiments conducted at the Technical University of Munich under Stefan Winter. One key lesson European timber projects teach is that when it comes to structural systems, weight matters. On average, mass timber assemblies weigh between one-third and one-fifth as much as concrete structures, despite equivalent structural capacities. As a result, mass timber buildings are much lighter than concrete ones, a positive for building in tricky urban situations, for example—where underground rail yards, subway tunnels, and municipal utilities place limits on how heavy and tall buildings can be. London-based Waugh Thistleton Architects (WTA), for example, recently completed work on Dalston Lane, a 121-unit CLT midrise complex located above a tunnel serving the Eurostar train line in the city’s Hackney neighborhood. For the project, the architects worked with timber-engineering specialists Ramboll to develop a stepped tower cluster rising between five and ten stories tall. CLT panels are used for the external, party, and core walls of the building, as well as the stairs and the building’s floors. The variegated massing is due directly to the architect’s use of CLT construction, which resulted in a lighter building that allowed the designers to build taller without more extensive foundations. The resulting building, with its staggered massing, better maximizes daylight infiltration into apartment units. The added height allowed the architects to add 50 more units to the project than originally permitted, a testament to just how light CLT can be. Andrew Waugh of WTA said, “Timber buildings are just simpler, cheaper, and nicer [than concrete ones]. High-density urban housing should be built using mass timber.” Lighter mass timber buildings also perform better in seismic zones. Since the lighter buildings carry less inertia, the potential for catastrophic swaying goes down. The strategy was applied this year with the Brock Commons tower, an 18-story, 400-bed college dormitory designed by Vancouver-based Acton Ostry Architects for the University of British Columbia Point Grey campus. The tower is made up of a hybrid structural system that includes CLT floor slabs, glulam columns, steel connectors, and dual concrete cores. The concrete cores anchor the light mass wood structure in place, helping to counteract seismic and wind-generated forces. The 173-foot-tall structure is currently considered the tallest mass timber building in the world, and the construction is particularly multifaceted, utilizing a specifically fabricated set of interdependent building materials and finishes to meet structural and fire-safety regulations. The Brock Commons tower’s hybrid structural system brings to light another valuable lesson: that above certain heights—ten to twelve stories—the lightness of mass timber construction becomes a liability with regard to wind loads. The lack of physical mass at the highest parts of a prototypical timber tower results in increased deflection from wind loads. Ola Jonsson, partner architect at Swedish architecture firm C.F. Møller, recommended architects “go back to thinking about construction when designing mass timber structures,” as a way of rethinking approaches to dealing with difficult-to-manage structural conditions. He added, “It’s so early [in the adoption of mass timber technologies] that few really know how to do it well.” The architect said that with certain tall timber tower projects the office is working on, designers had to develop new massing strategies to limit wind loads. Jonsson continued, “Many engineers lack experience in mass timber, so architects have to become central figures in construction and design during this early phase of adoption.” The firm is currently developing over ten mass timber projects, an emerging body of work that came out of earlier mass timber competition entries developed by C.F. Møller that took the world by storm. C.F. Møller recently entered into a partnership with HSB Stockholm—Sweden’s largest housing association—to design a series of new mass timber housing towers, including the 34-story Västerbroplan tower designed with concrete cores and wraparound terraces. The tower’s columns and beams will consist of a blend of CLT and solid timber. The building’s terraces will come with integrated exterior curtains and will be fully enclosed by a steel superstructure containing glass panels. The tip of the building is designed to dematerialize as it steps back along two facades, creating a series of exposed terraces and planted areas. Like Brock Commons, Västerbroplan tower features a hybrid structural system that is “resource-effective,” according to Jonsson, meaning both lightweight and rigid. The firm is also at work on a 20-story bundled housing tower called Hagastaden for HSB Stockholm, this one designed as part of a new quarter of the city that will contain mixed uses and generous pedestrian areas. The tower features varied floor heights designed to accommodate divergent uses like student flats, penthouse apartments, and typical family-occupied units. Aside from the firm’s multiple mass timber projects, C.F. Møller is working as part of an interdisciplinary research team that is developing new strategies around mass timber towers rising 20 stories or more. The group—backed by SP Technical Research Institute of Sweden, Växjö Municipality, and Linnaeus University, among others—will investigate mass timber construction from a fire-safety, life cycle, and construction technology perspective. Regarding the research project, Jonsson explained, "Massive wood constructions give urban planners, architects, and designers great possibilities to develop innovative and sustainable architecture,” adding, "but a broader knowledge and more practical experience in the industry is needed." Another paradigm-shifting impact mass timber construction has had on European building methods relates directly to the construction process. Because mass timber elements are factory-produced to order, the relationship between engineer, builder, and architect is extremely integrated. Cory Scrivner, mass timber specialist with Canadian mass timber manufacturer Structurlam, said, “For us, it’s all about the 3-D model. [Digital modeling and coordination] are all done before we go into production in the factory: Everything has already been approved by the architect, engineer, and our team.” Scrivner explained further that the intense coordination was necessary, as “we are designing a building made from components that are accurate within one to two millimeters of the digital model.” The designers behind Brock Commons utilized Structurlam as the mass timber manufacturer for the project. The advanced level of project coordination and off-site fabrication meant that project was finished roughly four months ahead of schedule, with a time-lapse video on a project website showing construction crews erecting upward of two floors per day. The first story for the project was built from cast-in-place concrete, while the remaining 17 stories are built in mass wood. The structural system utilizes glulam columns, steel connectors, and a two-way spanning CLT flat-slab. The design creates a floor beam–free structure that could be erected start-to-finish in nine and a half weeks. The rapid-fire construction time line, however, comes at the expense of longer planning and design phases prior to any work boots hitting the job site, as the teams must become absolutely synced prior to fabrication. Waugh of WTA explained that often with timber buildings, the firm asks its clients to “give us more time now [in the planning stages of construction] and we’ll save you even more time on the back end.” Waugh added, “The better programmed the construction process, the faster and more accurately the buildings come out.” Waugh said that after erecting several mass timber structures, the firm had “gotten so much better at it” than when they first started. One area of improvement has been material usage, which decreased with each project as the structural capabilities of mass timber have been further explored, tested, and certified. The Dalston Station project mentioned earlier, for example, utilized about two-thirds as much timber as the firm’s first mass timber project erected a decade ago. Part of the reason for the improvements, Waugh and Jonsson agreed, results from designers’ greater awareness of and comfort with the construction process. “To design well in mass timber, you need an architect who wants to understand that the nature of [the architect] is one of a ‘master builder’ as well as one of a ‘master designer,’” Waugh explained. Since mass timber construction methodologies are based on kit-of-parts assembly systems of mass-produced panel types and structural elements, there has been increased interest among European and Canadian firms in building high-density mass timber housing. These experiments have positive implications for the many American cities burdened with housing shortages and long project-approval times. Waugh explained that WTA’s focus rests on expanding the abundance of available housing through mass timber construction. He said, “We design everything in our office now as if it was a mass timber project. Concrete projects are becoming more and more rare.” Several projects in the works, like Shigeru Ban’s recently proposed 19-story Terrace House in Vancouver, Michael Green Architecture’s 35-story Baobab building in Paris, and PLP Architecture’s 80-story addition to the Barbican housing estate in London, point toward a wider adoption of tall and supertall mass timber housing towers. With faster construction times and fabrication that can occur in tandem with permitting, mass timber has the potential to help cities add housing rapidly, safely, and efficiently. Waugh added, “Humanity is becoming more urban, so the principal job of an architect in the 21st century is to develop high-density urban housing. In an era of climate change, it behooves you [as a designer] to reduce the amount of carbon emitted. Again, for us, mass timber is a way to do that.”
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The country’s tallest timber building wraps up in Portland

As the race heats up to demonstrate that timber is a viable alternative to concrete for mid and high-rise buildings, Portland, Oregon, has been leading the way in realizing mass timber projects. The latest to claim the country’s tallest timber building crown is Carbon12, an 85-foot tall mixed-use building in Portland, designed by PATH Architecture. Built with a mix of glulam beams and cross-laminated timber (CLT) surrounding a central steel core, the eight-story building was designed to have a minimal environmental impact and promote Oregon’s local timber industry. As downtown Portland addresses a growing demand for housing, timber projects constructed with prefabricated CLT panels cut off-site, like Carbon12, hold a speed advantage over traditional steel and concrete techniques. Carbon12 features a mix of 14 residential units, each with their own recessed balcony, as well as retail on the ground floor and a mechanized underground parking system. While the exterior is clad in vertically striated metal paneling that recalls timber grain, PATH chose to accentuate the natural materials of the interior spaces by leaving the wood columns, beams, and undersides of the CLT slabs exposed for a warmer feel. PATH’s focus on sustainability as a requirement in part drove their decision to use timber for Carbon12. Because locally grown timber can sequester more carbon dioxide than is used to grow and transport the wood, it often has a smaller carbon footprint in production than steel or concrete. Carbon12 will also feature solar panels on the roof. Although Carbon12 is currently the tallest timber building in the U.S., it won’t be for long. The 148-foot tall, 12-story Framework building, also in Portland, is shooting to take the title once it finishes in winter of 2018. Designed by LEVER Architecture and the Framework Project, Framework will feature a wood core as opposed to steel. Still, as timber buildings continue to push higher and higher, they may be paving the way for the eventual acceptance of timber as a mainstream urban construction material. Carbon12 is now fully complete and units are available on the market.
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2017 Best of Design Awards for New Materials

2017 Best of Design Award for New Materials: Indiana Hardwood Cross-Laminated Timber Project Designer: IKD Location: Columbus, Indiana The Indiana hardwood cross-laminated timber (HCLT) project is the first commercial pressing of HCLT and the first use of HCLT in a built project in the United States. IKD aspires to create a new timber product by upcycling low-value hardwood sawn logs that are extracted from Indiana forests. Indiana’s largest cash crop is hardwood, but over 55 percent of each log processed is of low value. The firm set out to demonstrate how low-value hardwood can be used to create high-value HCLT, which can then be used as the primary structure for buildings. This process has the potential to initiate a cascade of effects: positive job growth in rural forestry and manufacturing, hardwood lumber market expansion, forest land value increase, and improved forest management practices. HCLT offers numerous benefits over softwood, including superior mechanical properties, material volume savings, and increased fire resistance. “The use of hardwood in mass timber is appealing on many levels. Its added strength and durability over softwoods makes it ideal for exterior applications.” —Nathaniel Stanton, principal, Craft Engineer Studio (juror) CLT Fabricator: Smartlam Timber Engineers: Bensonwood General Contractor: Taylor Brothers Construction Hardwood Material Supplier: Koetter Woodworking Grant Funding: United State Forest Service Wood Innovation Grant
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2017 Best of Design Awards for Office & Retail

2017 Best of Design Award for Office & Retail: Albina Yard Architect: LEVER Architecture Location: Portland, Oregon

Albina Yard is the first building in the United States made from domestically fabricated cross-laminated timber (CLT). This new 16,000-square-foot speculative office building utilizes mass timber construction, with a glue-laminated timber frame and CLT panels manufactured and prefabricated in Riddle, Oregon. The project’s primary goal was to utilize domestic CLT in a market-rate office building that would pave the way for broader adoption of renewable mass timber construction technologies in Oregon and the United States. The design approach reflects a commitment to this sustainable technology by developing an architecture focused on economy and simplicity, material expression, and the careful resolution and integration of all building systems to foreground the beauty of the exposed Douglas fir structural frame.

“As a structural strategy, mass timber is very similar to a cast-in-place concrete structure in terms of layout and function of its individual elements. The main difference is the character and humaneness of the remaining spaces.  It is very well-suited for this type of use.” —Nathaniel Stanton, principal, Craft Engineer Studio (juror) General Contractor: Reworks Structural Engineer: KPFF Consulting Engineers CLT Supplier: DR Johnson Lumber CNC Routing: Cut My Timber   Honorable Mention Project: Cummins Indy Distribution Headquarters Architect: Deborah Berke Partners Location: Indianapolis, Indiana This new office building reinforces an active pedestrian experience that is connected to downtown Indianapolis and its parkland. The unusually slender floorplan and high ceilings provide abundant natural daylight for every space and minimize reliance on electricity. A high-performance “calibrated” facade and an integrated system of fins and shades limit heat gain and increase thermal comfort.   Honorable Mention Project: Zurich North America Headquarters Architect: Goettsch Partners Location: Schaumburg, Illinois Located on a 40-acre expressway site in suburban Chicago, the North American headquarters of the Swiss Zurich Insurance Group reflects the company’s global reach and commitment to sustainability. Composed of three primary “bars” that are offset and stacked, the arrangement creates unique spaces for collaboration, opens views of the surrounding landscape, optimizes solar orientation for amenities, and provides programmatic flexibility.
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Microsoft reveals renderings for its new Silicon Valley campus upgrade

Microsoft has gone big and broken ground on its new Silicon Valley headquarters, with a sustainability-minded plan to modernize its Mountain View, California outpost. The 32-acre campus might seem small when compared to the company’s sprawling, 500-acre flagship location in Redmond, Washington, but Microsoft’s pursuit of a net zero non-potable water certification under the Living Building Challenge will make them the first tech company to totally reuse non-potable water. The redevelopment plans come as WRNS Studio replaced SOM early last year as Microsoft’s designers of choice. The redevelopment is leaning hard on a green modernization, with Microsoft pursuing LEED Platinum certification for all of its new buildings, committing to the WELL Building standards for the interiors, and integrating cross-laminated timber (CLT) throughout all of the new buildings to cut material usage. In trying to meet their water-use reduction goals, and acknowledging California’s limited groundwater availability, the campus will feature rainwater catchments and an on-site wastewater treatment plant so that drinkable water can be recycled for other uses. Because the campus is next to Stevens Creek, the tech giant is also introducing a 4-acre, occupiable green roof solely planted with native species. Rooftop solar panels will also help cut the campus’s energy usage, while the buildings will let natural light in through their uniformly large windows. Not to be outdone by the main, Seattle-adjacent campus, the project will also include an underground parking garage topped by a soccer field and a new athletics facility, while returning the former parking lots to nature. Besides modernizing the office space of their 2,000 San Francisco Bay Area-employees, the new campus will feature a renovated dining hall, new theater, conference center, and a “Microsoft Technology Center.” Microsoft has provided a full fly-through video of their plans below. The new Mountain View campus plan increases the existing 515,000-square-foot campus to 643,000 square feet, and comes amidst the recent opening of Apple’s new space-aged campus nearby. Similarly, Microsoft's renovation of its main headquarters in Redmond, announced at the same time as its Silicon Valley campus, feels like a direct response to Amazon’s city-hopping HQ2 plans. Microsoft's Silicon Valley campus is on track to re-open sometime in 2019.
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New timber research finds exciting potential in steel and concrete composites

With mass timber projects on the rise around the United State, Skidmore, Owings & Merrill (SOM) and Oregon State University (OSU) have partnered to produce two new reports on how timber buildings can overcome their technical limitations by integrating steel and concrete. The new composite systems being proposed would allow timber construction to rise higher than before, with longer floor spans. The OSU Testing Report, released earlier this month, looked into the possibility of combining cross-laminated timber (CLT) floor systems with a concrete topper, to improve the strength of the flooring as well as lengthen its span. To accurately represent real-world conditions, the SOM team first drew up plans for a “typical” 11-story residential building and indicated where the wood columns would normally be. With the floor span determined, the CLT flooring was stress tested for load, bending, cracking and shearing, before and after the application of a concrete slab. A 2.25-inch thick concrete layer was applied over a 6.75-inch thick CLT floor for the experiment. After testing smaller, individual sections, an eight-foot-by-36-foot full-sized mockup was created and subjected to load testing, only failing after engineers applied eight times the normal service load, or around 82,000 pounds of pressure. One complicating factor is that CLT can be charred for a higher fire rating at the expense of its strength, and any real-world application of CLT would need to be thicker than in testing conditions. Still, the results are a promising first step to increasing floor spans in timber buildings as well as improving their acoustic properties. The second report was produced in conjunction with the American Institute of Steel Construction (AISC) and examined how steel framing can best be integrated with timber floor systems. Because steel framing can span much greater distances than timber with smaller columns, and because CLT is lighter than concrete, a building that uses both should get the best of both worlds. In SOM’s modeling, this combination model was equally as strong as a steel and concrete building while offering window bays of the same size as a typical residential building. Ideally, high-rise timber construction of the future would combine both of these techniques, as the concrete slab topper adds extra seismic protection. With timber construction offering the potential for more sustainable, durable and quickly assembled towers, hybrid research could be a stepping stone towards bringing mass timber construction into the mainstream. All of SOM’s timber research reports can be found here.
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Arbora housing complex in Montreal points to the future of timber construction

This is an article from our special November timber issue. Comprising three eight-story buildings totaling just shy of 600,000 square feet, the Arbora Complex near downtown Montreal is one of the largest mass timber projects in the world. The notability of this project is not just its size, but its ability to be a competitive, marketable, environmentally responsible alternative to increasingly affordable steel and concrete construction—an ability we might not associate with mass timber structures. The $130 million project offers 434 units, 130 of which are rental. According to U.S. Market Development Manager Jean-Marc Dubois at Nordic, a Quebec-based company that, among other services, supplied wood for the project, “The market in Montreal is more suppressed than Vancouver and Toronto. To be able to build means you must have a design that is viable and efficient—something that brings value to the developer. There’s a lot of press surrounding high-rise wood construction, but Arbora shows there’s a place for affordable, viable mid-rise construction.” Arbora involves cross-laminated timber (CLT), composed of layers of dimensional lumber stacked perpendicularly and glued together to create structural panels. CLT panels are typically made of layers of three, five, or seven, and, because they offer two-way span capabilities, can be used for floors, walls, and roofs. The result is a material that is lightweight, strong (up to seven times the strength of concrete), efficiently shipped, and less labor-intensive than its steel and concrete counterparts.
“With mass timber structures, you can use less employees and get more work done,” said Dubois. “There’s a shortage of skilled labor across North America, so the fact that you can raise structures with considerably less skilled employees is very critical. Typically we operate with as few as four to six tradespeople on a jobsite. The output per person is much greater.” These benefits come with a cost, however: increased upfront coordination and design time. Engineered wood components are designed, optimized, cut to millimeter precision, and then shipped to site for assembly. Dubois reports that Nordic is involved on multiple fronts of mass timber projects like Arbora, coordinating design, engineering, fabrication, construction sequencing, and regulatory parameters. “This is one of the things that distinguishes Nordic,” he said. “There’s a tremendous amount of involvement and engagement with our team that you don’t necessarily see as you’re looking at the construction process. We’re taking an active role in the design process, in addition to sitting in meetings with local authorities.” The key to Arbora’s commercial success in a competitive housing market is design efficiency, and an acknowledgement of the inherent structural properties of CLT from the outset of a project. “There are efficiency gains in replication,” Dubois said. The project was organized around a 20-foot grid, an ideal structural span and shipping dimension for the beams and panels. The consistency of the grid allowed an efficient manufacturing process, and abbreviated on-site assembly time. Early adopters of CLT in North America have tended to be more custom projects like schools and sports venues, but Dubois sees demand for mass timber shifting into commercial real estate, namely office workplace typologies, where the unique look of a wood structure can offer differentiation in the marketplace. Mass timber adoption in the United States has lagged behind that in Canadian markets. Dubois attributes this to a number of factors including the litigious nature of the United States, and the tendency of Canadian authorities to be receptive to performance-based design. “In Quebec, we don’t promote one building material over another, so we have to make a market against steel and concrete, which is exceedingly inexpensive,” he said. “We have to be economically viable and prove we are meeting the same structural and safety requirements that other systems must abide by. “Performance-based design typically runs into more red tape in the United States,” he continued. “I think it’s a fear of the unknown. This has led the American Wood Council, the U.S. Department of Agriculture, and the wood industry to promote the tall wood agenda, to try and get coded options so that it is prescriptive as opposed to alternative means and methods.”
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Congress gears up for a fight over mass timber legislation

This is an article from our special November timber issue. The battle over the 2017 Timber Innovation Act is gaining momentum in Washington, D.C., where two new Senate sponsors and four new Congress members have signed on to it since this past May. The pending legislation would provide funding for research into innovative wood materials and mass timber structures above 85 feet. The bill’s proponents are hoping that it will be an impetus for transforming cities and towns across the country with a bevy of mid-rise and high-rise mass timber buildings. “I am very impressed with the large cross-aisle support,” Chadwick Oliver, director of Yale University’s Global Institute of Sustainable Forestry, said. “You have Bruce Westerman, a Republican congressman from Arkansas and Peter DeFazio, a Democrat from Oregon who has been on the side of environmental groups. This looks like a bill that is quite serious about moving forward.” However, the concrete and steel industries are vigorously lobbying to derail the legislation, and have established a website called Build with Strength that contains a detailed critique of the new generation of wood buildings. “It is a piece of legislation that props up one industry over another and we think that it is misguided and dangerous,” Kevin Lawlor, a spokesperson from Build with Strength, said. “We don’t think that it is safe in three-to-five story buildings, and we don’t think that it is safer in taller buildings.” The wood products industry, the U.S. Forest Service, and other advocates claim that technological advances make the new generation of tall timber buildings more fire resistant. In fact, according to Dr. Patricia A. Layton, director of the Wood Utilization + Design Institute at Clemson University, that is because of the way it chars in a fire: By insulating its interior, an exposed wood beam can actually be structurally stronger than a steel one. “Steel loses its strength at a lower temperature than does wood,” she explained. “If you expose concrete or steel it is combustible, and it does feel the effects of fire.” Many of the act’s supporters say that allowing buildings to be built from wood technologies such as cross-laminated timber (CLT) will result in a host of economic and environmental benefits. Most of the Timber Innovation Act’s sponsors hail from states where the wood industry is struggling to recoup from the recent housing downturn and also suffering from the decrease in demand for paper that is a result of the increasing digitalization of the economy. “A big part of the innovation act is having the U.S. Forest Service work to expand markets and attract business to heavily forested states, particularly those that have a major timber industry,” said Andrew Dodson, vice president of the American Wood Council, who notes that the U.S. Timber Innovation Act is a way to help jumpstart a sagging wood-products industry. “Mills are running at much lower capacity,” he said, “two shifts versus three or four—we want to put more mill jobs back in place.” However, some in the mass timber industry say that the Timber Innovation Act will be of limited utility until building codes are changed to allow for the use of CLT. “The code issue is more critical than the Timber Innovation Act,” Jean-Marc Dubois, director of business development for the Montreal-based Nordic Structures, said. He believes that New York City’s restrictive building codes have helped stall progress on tall timber, pointing to the wooden skyscraper designed by SHoP architects that was killed earlier this year as an example. Even though the 2015 International Building Code (IBC), which New York City has not adopted, allows for the use of CLT, Dubois said that building departments throughout the country haven’t updated their codes to allow for the use of CLT. Having the SHoP project, which received a lot of publicity, fail to get built was a major setback for the industry, according to Dubois. “New York City had the ability to be a real-world leader with timber innovation,” he said. “It was disappointing.” A $250,000 grant from the U.S. Forest Service’s Wood Innovations Grant program helped Yugon Kim of Boston-based IKD develop what he believes is the first hardwood CLT structure in the U.S.: An outdoor sculpture in Columbus, Indiana, which consists of a series of ascending arcing forms. Congress is not the only place in Washington where the merits of tall mass timber are being explored. Steve Marshall, assistant director at the U.S. Forest Service, has been working with the International Code Council to develop standards for the use of CLT. In addition, the U.S. Department of Defense has been conducting blast tests with CLT to determine whether it is an appropriate material to use on its bases. Marshall said there are other potential sources for government support for CLT projects aside from direct funding from the Timber Innovation Act. In the third week of October, his agency will be releasing a new round of grants of up to $250,000 under its Wood Innovations Grants program. Next year, the Forest Service is planning on making $8 million available under the same program, and applications will be due by mid-January. One of the most notable examples of how government funding can play a difference is with LEVER Architecture's innovative design of the 12-story (148-foot-tall) Framework building under construction in Portland, Oregon, which will be the first wood high-rise in the U.S. A $1.5 million U.S. Tall Building Award sponsored by the U.S. Department of Agriculture helped fund the seismic and fire-safety tests that enabled it to pass muster with Portland building department officials. Thomas Robinson, principal of LEVER Architecture said that the concrete and steel industries shouldn’t be worried about losing market share because in the future most tall timber structures will be hybrids that include concrete and steel as well as wood. “We need to look at each material for its appropriate purpose,” he said.
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Is mass timber really sustainable?

This is an article from our special November timber issue. We like to blame a lot of things for climate change—namely coal and cow farts—but if we were to search for a worthy scapegoat, architects might end up looking in the mirror. The building sector is responsible for 44.6 percent of U.S. carbon dioxide (CO2) emissions. And, with an estimated 1.9 trillion billion square feet to be built in the next 33 years, those emissions will not subside without significant intervention. On the flip side, for architects anyway, this means the power to reduce carbon emissions is quite literally in your hands. “No designer—I think—wakes up and says, ‘I want to make the world worse today,’” William McDonough, architect, designer, and sustainable development leader said. “To make the world better, that’s our job.” Identifying successful ways to build sustainably can be difficult in a haze of greenwashing and checklist-style certifications, but many environmental experts, architects, and scientists are looking to mass-built timber as a reliable way to reduce carbon and fossil fuel output. A recent study, “Carbon, Fossil Fuel, and Biodiversity Mitigation with Wood and Forests,” stated that using wood as a building-material substitute could save “14 to 31 percent of global CO2 emissions and 12 to 19 percent of global FF [fossil fuel] consumption by using 34 to 100 percent of the world’s sustainable wood growth.” Building with timber reduces the overall carbon footprint in several ways. First, wood is a renewable resource, and growing a tree is a low-impact method of production (i.e. it uses photosynthesis rather than a plethora of machines). Second, trees are grown in abundance all over the United States and don’t need to be imported from abroad, reducing the amount of energy expended on shipping. “Right now we harvest less than half of what we could and still be well within the threshold of sustainability,” Kathryn Fernholz, the executive director at Dovetail Partners, an environmental nonprofit, explained. “That’s not the same in every single scenario, but in general in the U.S., we have an abundance of wood.” Third, and perhaps counter-intuitively, many environmentalists believe that harvesting trees allows forests to become more efficient at carbon sequestration. The logic is simple: When a tree is harvested, it stores carbon, then when another tree is planted in its place, it also will store carbon, making that plot of land’s carbon sequestration infinitely multipliable as trees are planted, grown, and harvested. “There is a widely held belief that cutting down trees is bad and causes loss of forest, but a strong market for wood products would cause us to grow more forests,” Fernholz said. “The vast majority of deforestation is land conversion, using the land for something else like development or agriculture. We know what resources we have and we monitor them and adjust. Forestry is not in the same place it was a hundred or even fifty years ago when deforestation was an issue.” While that stance of de-and reforestation is under debate among environmental experts, across the board, timber is generally a more sustainable building material because it is a renewable resource (provided that responsible forest practices are used). This includes the energy consumed to produce cross-laminated timber (CLT) in factories, which have a carbon emissions advantage over steel because the wood does not need to be heated over 2,700 degrees Fahrenheit like steel or concrete—in fact, unless the wood is kiln dried, heat isn’t need at all. Although embodied carbon is typically measured per building, because different amounts of each material are used in different scenarios, Wood for Good, a campaign by the timber industry to promote the material, claims that a ton of bricks requires four times the amount of energy to produce as a ton of sawn softwood (wood used for CLT); concrete requires five times, steel 24 times, and aluminum 126 times. “Reporting carbon emissions for wood includes a range of different assumptions and methods,” explained Kathrina Simonen, an associate professor of architecture at the University of Washington and director of the Carbon Leadership Forum. “So sometimes it ends up negative and sometimes it ends up positive. It can be confusing.” She is optimistic, however, that research is close to resolving the differences. Responsible forestry practices are already underway, with harvest occurring on long rotations so that the forest has time to regenerate itself and care can be taken to avoid removing other plants, roots, and branches in the process. Lastly, “Wood can be a durable good, as we've seen in ancient wooden buildings like the Temple at Nara, Japan [originally built in 745 AD and rebuilt in 1709],” McDonough said. “In [wood’s] history, it is often put into a cycle of use and reuse that can take it from large numbers to smaller and smaller [components].” Its ability to withstand centuries and to be disassembled and then reassembled into other buildings and furnishings keeps it out of the landfill and in a perpetual cycle of use until it can ultimately be returned to the environment in some form. Although well over 90 percent of one-to-three-story residential buildings are already wood-built, there are only a handful of mid-rise and tall timber buildings across the United States, a result of building codes that often prohibit timber-built structures larger than four to six stories. However, thanks in part to innovative wood products, including CLT, nail laminated timber (NLT), and glue laminated timber (glulam), wood construction can be used in buildings as tall as 40 stories. A study by consulting and engineering company Poyry and the New England Forestry Foundation shows that the greatest potential for timber-built is in mid-rise (six to 14 story) buildings, as it also tends to be more economical to build with timber at that scale. According to the Soft-wood Lumber Board, over two-thirds of the square footage in the mid-rise sector could be made with mass timber. These statistics combined, in addition to the taller structures that mass timber can create, have the potential to make a sizable dent in our CO2 and fossil fuel emissions. Like virtually everything in architecture, though, it is all in the details; for timber to be sustainable it has to be done correctly, from responsible forestry practices to environmentally safe glues and binders to craftsmanship and the design itself. “It is tremendously exciting. Building with wood creates diverse opportunities—there are different species and materials that all can work,” Fernholz said. “However, it is important to recognize that some things can come from wood, but nothing replaces good design and planning.”
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Cross-laminated timber could lead a mid-rise revolution

This is an article from our special November timber issue. Engineers specializing in cross-laminated timber (CLT) see its future less in boutique prototype towers, requiring case-by-case demonstrations for approval, than in a meat-and-potatoes mid-rise market. While, according to Colorado State University's John van de Lindt, “some of those pioneering early CLT buildings are really almost like a partial R&D project in disguise,” he and colleagues predict that the field's maturation depends on the incorporation of research-driven CLT standards into building codes. “If you're going to just do a two-story residential home, you have a perfect design code pathway to do it,” said Shiling Pei of the Colorado School of Mines, chief investigator on a National Science Foundation (NSF)-supported study of seismic design methods. “But if you want to go taller, especially [if] you want to go above 85 feet— that is currently IBC [International Building Code] for Type IV, heavy timber—then you have to do something else...a lot of testing to try to convince the local building-code officials.” He views CLT beyond about 20 stories skeptically, on economic grounds: “In my projects, I say it's tall wood; it's not high-rise wood.” Pei cites the 2011 CLT Handbook by Canadian nonprofit FPInnovations as a pivotal document, republished in a 2013 U.S. edition with input from the American Wood Council (AWC), Forest Products Laboratory, WoodWorks, and APA: The Engineered Wood Association (formerly the American Plywood Association). In 2011, APA and the American National Standards Institute developed a performance-based standard, PRG 320, updating it in 2012 and 2017; it offers detailed specifications on CLT products' composition, dimensions, shear strength, stiffness, and other properties. The AWC's National Design Specifications for Wood Construction and the IBC include basic CLT sections in their 2015 editions. Since seismic risks in Europe (Italy excepted) are milder, the transfer of CLT technology to Canada and the U.S., particularly for larger scales and open plans, requires standards addressing lateral forces. The next hurdle is for the American Society of Civil Engineers' influential code book, ASCE 7: Minimum Design Loads for Buildings and Other Structures to address CLT, particularly its response-modification coefficient or R factor (not to be confused with R values for thermal resistance) in its seismic design provisions. “To make [CLT] economically competitive,” van de Lindt said, “it really needs to have these seismic performance coefficients (essentially an R factor) in the code, so that people don't have to get special permission every time they want to use it,” incurring engineers' reviewing costs. Results of van de Lindt's R-factor studies are expected next year, and the code-revision cycle takes about five years; if a proposal based on the findings passes review by Building Seismic Safety Council committees and a public-comment period, it should enter the 2022 edition of ASCE 7, then IBC. “With CLT, everything rotates like a rigid body under seismic stresses," van de Lindt said. "Panels do not deform enough to dissipate energy and suck load right into them.... For a steel special moment frame that's detailed for seismic, it can be an R of 8, [which has] a lot of ductility.” Yet adding concrete or steel lateral systems, as in Brock Commons (Acton Ostry Architects, Vancouver, page 12) and Carbon12 (PATH Architecture, Portland), respectively, requires multiple trades on-site and squanders CLT's construction speed. Advanced “disruptive technologies” common in Japan (base or inter-story isolation using sliders, rockers, or damping devices) require special review. Very tall wood, 20 stories and above, he believes, calls for performance-based modeling rather than prescriptive tables and “will always require review, at least in our lifetime.” Andre Barbosa of Oregon State University's School of Civil and Construction Engineering and Tallwood Design Institute concurred, noting that CLT projects above about ten stories are often hybrids with concrete cores or steel for lateral resistance. “You get the best out of both materials. You have the CLT that's lighter; [its] strength-to-weight ratio is very, very good. You get the concrete that allows you to go to longer spans, but also it creates that natural barrier for smoke and essentially for fire across floors.” Current methods of addressing timber's susceptibility to moisture and insects are generally adequate, he says, adding that long-term deflection (creep) in CLT buildings tall enough for large loads needs further study. Supported by the NSF's Natural Hazards Engineering Research Infrastructure Tall Wood program, Pei and colleagues recently built a two-story prototype for testing on the world's largest shake table at the University of California San Diego. Simulating 14 quakes of varying severity up through a "maximum credible earthquake," a once in 2,500-years event, “the building essentially received no damage, and we don't need to repair anything,” Pei reported, noting that CLT rocking walls actually outperformed their concrete and steel counterparts in resilience. His next studies will test a ten-story building under combined seismic stress and fire; the experiment has earned the inevitable nickname “shake and bake.” Flammability is “a concern very often expressed, but an easy one to dismiss,” said Lech Muszynski, associate professor of wood science and engineering at Oregon State University's College of Forestry. Studies support the counterintuitive idea that charring produces an insulating layer that actually slows pyrolysis, making it advance predictably and sparing enough wood to pass two-hour fire-resistance tests. “I've done some testing on unprotected CLT assemblies here in the states, large-scale floor and wall assemblies; there is a large library of similar tests being done in Europe in the past,” Muszynski reported, crediting Ario Ceccotti of the Istituto per la Valorizzazione del Legno e delle Specie Arboree (Trees and Timber Institute) for similar research in Italy and Japan. These tests have largely involved exposed CLT, though in practice the material is commonly encapsulated in gypsum board, adding another hour or so to its fire-resistance rating. Two commercial CLT manufacturers in the U.S., Muszynski noted, Oregon's D.R. Johnson (which he advises) and Montana's SmartLam, have their products fire-certified. Steel components within joints, Muszynski added, are more vulnerable than the wood. He uses a photo from the 1906 San Francisco fire to illustrate “the difference between flammable and fire-safe”: A severely burnt wooden beam shows charring and exposed nails, indicating deep fire penetration, but remains rigid, while two heat-weakened steel beams flop across the wooden member, resembling soggy pasta. Adhesives also require attention: Some bonded timber products use melamine urea-formaldehyde resins, which harden under heat, but the more common adhesive is polyurethane, which softens if the char reaches bond lines. Moisture can be more hazardous when worksite protections are lacking: Muszynski recalls an Italian project where financial delays left a site idle for several months, exposing CLT to rain—and underscoring the importance of using contractors familiar with the material.
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How mass timber could transform our cities (really)

This is a preview of our special November timber issue. Mass timber is having its Maison Dom-Ino moment. At the 2014 Venice Architecture Biennale, a curious structure sat on the grass near the international pavilion in the Giardini. It was an engineered timber version of Le Corbusier’s Maison Dom-Ino, the seminal, prototypical reinforced concrete project, which was celebrating its 100th birthday. As a manifesto of sorts for modernism, the original Maison Dom-
Ino sent shockwaves through the 
architecture world and the built environment at large. It was a replicable, scalable building system made from simple columns and floor slabs, which could be stacked vertically and horizontally like dominoes. The 2014 version was commissioned by Brett Steele, then dean at the Architectural Association School of Architecture in London. He described the “afterlife” of the 1914 Dom-Ino as “a set of guiding, abstract, and idealized principles” that have shaped the world as we know it today. The choice of timber in this case is an interesting one, as mass timber seems to be today’s material that looks promising for the future, much like steel and concrete did in the 20th century. As outlined in this issue, timber has a litany of benefits including carbon sequestration, lower embodied energy than steel and concrete, psychological benefits for inhabitants, less construction noise in tight urban sites, easier on-site construction in general, and many other positive aspects. It would reorient wood from light-frame suburban development toward mid-rise dense urban development. Taller and taller timber towers serve as the “Eiffel Tower” moments for the rapidly expanding timber industry, as pointed out by Jimmy Stamp in the Smithsonian Magazine article, "Is Timber the Future of Urban Construction?" And these important projects have brought attention to an otherwise niche building trade. Alongside these "Wow!" projects, there is another, less sexy side of the timber revolution that could help to change the way we build in America. New technologies abroad are already making mid-rise construction cheaper and more viable at larger scales. This incremental progress is taking place among manufacturers, architects, engineers, and designers as we speak in places like the nearly 600,000-square-foot Arbora complex in Montreal, Quebec. And companies, such as Nordic Engineered Wood, are expanding in the U.S. market, a place known for innovation that makes things cheaper and more market-ready. Once the market can produce mass timber structures more cheaply than steel and concrete, there could be a seismic shift. And as timber becomes more viable for safety concerns, and more legal through local codes adapting ("The State of the Art of Timber"), we could see timber proliferate at the same rate as the early-20th century saw the Maison Dom-Ino’s system spread across the world over the next 100 years. But of course we are speculating a bit in this issue. The future is not so clear. A fight is brewing in Congress ("What Wood You Do?") over the bipartisan Timber Innovation Act (and along with it, lobbying antics from the steel, concrete, and sand industries). If U.S. governmental agencies and private companies—namely manufacturers—come together, the costs could come down. It is possible that architectural knowledge-research and development could bend the markets so as to impact both economic and environmental resource allocation networks toward a lower-carbon future, as architect and timber expert Alan Organschi told AN in a conversation. The arms race is already on, and the National Forest Service has awarded $250,000 to Boston-based IKD to develop a hardwood-based cross-laminated timber (CLT), which is an important incremental step in the process. This issue speculates on a future where entire blocks might be built with green technologies including mass timber, and whole cities could be filled with beautiful wood buildings layered onto the stone, brick, steel, glass, and concrete urban fabric. How this revolution might play out is unclear, but we are seeing glimpses of what might be to come, such as Framework by LEVER Architecture in Portland, which will be the tallest timber building in the U.S., or the work of Michael Green Architecture in Vancouver, or Gray Organschi Architecture out of New Haven, Connecticut, which has been researching mass timber at the Yale School of Architecture. We also look to Europe and Canada for success stories that might be examples for the future of mass timber in the U.S. As Steele said of his 2014 Maison Dom-Ino, “This initial installation will remind visitors not only of modern architecture's most foundational project, but of an architectural instinct made even more apparent today than it was at the time of its original conception; namely that architecture always operates in the space created by a contrast between architecture as already known, and what it might yet become.” Can we imagine a partially wooden future? This article will be updated with links to other articles from the November timber issue.