Saving America’s forests one wooden high-rise at a time
Posted: February 16, 2016Source: E&E News
Photo courtesy of FTPEdelman.
If the invention of steel forged the high-rise, the iconic building’s future may be pine.
This fall, the future will be under construction in the United States. A 12-story high-rise built primarily of wood is set to go up in Portland, Ore., like giant Lincoln Logs extending more than 100 feet into the air. When finished, the project named Framework will be the tallest building in the country to be constructed with a promising engineered wood material, cross-laminated timber.
This feat of wooden engineering is something the Department of Agriculture as well as the wood products industry is hoping to use to start opening up the tall building market — traditionally cornered by steel and concrete — all while bolstering rural economies and fighting climate change.
“There is a huge amount of interest both from the architectural community and from the sustainability community relative to the carbon sequestration wood offers and the benefits it offers for managing forests,” said Thomas Robinson, a principal architect with LEVER Architecture, one of the firms designing the Portland project.
Proponents of cross-laminated timber and other mass timber products say it could create demand for the woody material clogging overgrown forests, especially in the West. Creating a market for small-diameter trees or diseased or burned forests by turning it into a high-value building material would create jobs, something once-great rural paper mill towns desperately need.
USDA, the Forest Service’s Forest Products Laboratory and a handful of the forest products industry groups have jumped in the cross-laminated timber game, throwing money at educating engineers and architects, promoting the product, and moving forward with research.
For the building’s owner, the new space, which will be located in Portland’s quirky Pearl District, needed to balance sustainability with practicality. When the project team at LEVER Architecture heard about a competition hosted by USDA calling on developers to use wood to build tall buildings, “the stars aligned” for cross-laminated timber, said Anyeley Hallová, a partner on the project.
Last September, USDA, along with the Softwood Lumber Board and Binational Softwood Lumber Council, awarded the Portland project and another in New York City a total of $3 million to construct tall wood buildings to serve as demonstrations that wood can be the principal building material for multistory, nonresidential buildings.
“I think the reasons for interest on the part of [Agriculture Secretary] Tom Vilsack are many, one of which is the potential for jobs in America. Cities are thriving, but the countryside isn’t, especially communities in highly forested areas,” said Jim Bowyer, director of the responsible materials program at Dovetail Partners, a nonprofit environmental consulting firm. “USDA sees an opportunity for wood to play a bigger role in carbon mitigation, too.”
Sometimes described as “jumbo plywood,” cross-laminated timber (CLT) is made when smaller pieces of timber — two-by-sixes and two-by-fours — are glued together with the wood grain alternating at 90-degree angles. Sheets of the glued timber are layered together into large sheets, up to 18 inches thick, 10 feet wide and upward of 50 feet long, and can be used just like steel or concrete would as walls, ceilings or floors.
The material is strong, yet lighter than traditional building materials and full of carbon. Cross-laminated timber buildings go up in a small fraction of the time of those made from steel or concrete.
But some questions remain about building tall with wood. Won’t it burn? Are wooden high-rises giant termite buffets? How does wood hold up against earthquakes or humidity? And these questions have to be answered before CLT is sanctioned by building code officials and can join steel and concrete as a truly competitive building material for high-rises across America.
Finding the ‘sweet spot’ for wooden high-rises
There is a lot of wood in Michael Ritter’s office, which makes sense since Ritter is the assistant director of the wood products research group at the Forest Products Laboratory in Madison.
Samples of cross-laminated timber and other forest products litter his bookshelves. On a table sits a shoebox-sized model of an all-wood tornado safe house one could build for a few thousand dollars with wooden materials from Home Depot, a testament that the lab’s job is to broaden the market and uses for wood products.
Ritter’s latest project was to bring more than 120 researchers and engineers from the United States and abroad for a two-day rendezvous at the lab to discuss what the research priorities should be for CLT. The lab will soon release a report spelling out what those should be.
“I think that’s going to be a real important outcome,” Ritter said. “Both research and technology transfer are critical, and then communicating research activities and findings is also a priority.”
Cross-laminated timber is not new, per se. In the last few decades, European builders, engineers and architects have quietly developed the material.
In the last five years, 17 buildings ranging from seven to 14 stories tall have been constructed using mass timber around the world, the majority in Europe.
The United States has been slow to embrace wood for building more than a few stories high. But some see the tides starting to turn.
Jennifer Cover, executive director of WoodWorks, an educational arm of the Wood Products Council that provides free education to architects and engineers on designing and building nonresidential buildings with wood materials, said in the last three years her organization has seen interest and requests for assistance skyrocket.
Currently, the group is providing technical assistance to 22 U.S.-based projects that are slated to build past seven stories with wood.
“The momentum is there for sure,” she said. “Engineers are going to decide where the sweet spot is, where it makes the most sense. Seven, eight stories up to 13 to 14 seems to be very doable with wood as the primary material.”
Research takes time
Designing a building using cross-laminated timber or other mass timber products is a different beast from more traditional wood design in part because of the way CLT is manufactured — in large panels or plates. Based on the design of the building, a computer-controlled machine will control a robot that cuts slabs of cross-laminated timber so they will fit perfectly together. The slabs arrive to the job site, and the whole thing goes up like a big Erector set.
“The greatest hurdle is the perception that we know less than we actually do,” Cover said. “We’ve definitely heard time and again that it isn’t a huge learning curve after you get through that first project.”
The Forest Products Lab began studying how the material holds up against earthquakes about four years ago with the goal of developing a design procedure for the material that is code-compliant for midrise buildings. The lab’s research is not complete. But research from other countries like Japan finds the wood’s flexibility allows it to perform as well as, if not better than, steel and concrete in an earthquake.
Another cause for concern — one Bowyer calls “quite legitimate” — is how the material performs against fire. Here, too, the research seems to indicate wood outperforms steel, which is highly susceptible to heat.
“As wood burns, it forms a char layer, which is an extremely effective insulator,” he said. “Even through an intense fire, wooden beams will remain standing, whereas steel beams will heat up and bend over them.”
Research is being conducted to see how much exposed wood can be subject to fire before it contributes to a blaze.
“The research is a very rigorous process,” Ritter added, setting a sample of cross-laminated timber made with three-quarter-inch laminate on the table. “So even though we’re scheduled to do the final phase of the research on seismic design, it may still take six years, seven years down the road to get it in the code.”
A building codes problem
Kenneth Bland, vice president of codes and regulations with the American Wood Council, said although the industry wants to build taller with wood, the codes aren’t there yet, and that is preventing wide-scale adoption.
Most homes are constructed with a wood frame. In the nonresidential space, however, anything taller than six stories has been appropriated to steel and concrete through building codes.
One challenge is that getting new codes approved by the International Code Council, the nonprofit that develops building standards, is a three-year cycle. Bland and his staff submitted a proposal for a nine-story mass timber code, which was denied. The next opportunity to submit a new proposal will be in 2018, for the 2021 codes.
Code officials may be opening up the lines of communication. Last month, the ICC board of directors voted to create a Tall Wood Ad Hoc Committee, which will study tall wood construction and may develop code changes to be submitted for the 2021 International Building Code.
Inside the biggest installation of CLT in the U.S.
Outside of the testing and scheming to bring cross-laminated timber to the mainstream, early adopters have found the material adds something timeless and natural to their structure, while the environmental benefits bolster sustainability goals.
Melodic piano music envelops visitors as they step into biotechnology company Promega Corp.’s Feynman Center, located at the company’s Madison headquarters. A mix of laboratory, manufacturing and meeting spaces, the 260,000-square-foot building was completed in 2014 with the hope of balancing functionality with comfort, said Jennifer Romanin, director of in vitro diagnostic operations.
The space goes to great lengths to accomplish that. Many aspects of nature — from 18,000-pound boulders to a lush two-story-tall living wall that grows and blooms year round — greet visitors when they arrive. The biggest component of the building, however, is its primary building material: 14,133 cubic feet of cross laminated timber, what is believed to be the largest installation of the material in the United States.
The total carbon benefit between carbon stored in the wood and greenhouse gas emissions prevented is estimated at 692 metric tons.
“Especially here in the Midwest, I think we see a lot of wood, but to see the structure the way it was designed, and all the wood in the columns and beams, I think that is what helps it stand out,” Romanin said. “One of the words we used to describe what we wanted to evoke was ‘timeless’ — what about wood isn’t timeless?”
The option to use cross-laminated timber was introduced to Promega by the architectural company with whom it worked and trusted. Still, there were questions about fire safety and the performance of the wooden material. The Forest Products Lab continues to monitor how moisture is affecting the building through the use of remote sensors. So far, everything looks normal.
All the cross-laminated timber used at the Feynman Center originated in Canada, which highlights another challenge for the material: a lack of manufacturers based in the United State.
There are only a handful of facilities in the country that make CLT, including one in Oregon and one in Montana.
“In the business of supply chains, competitive bidding is very important,” Bowyer said. “It’s a chicken-and-egg thing. Prices will come down, the price of shipping will come down, but only if we get more producers.”
The Portland project is hoping to source at least some of its cross-laminated timber from the Oregon plant. The USDA grant will help pay for seismic and acoustics research and testing on the building, with the findings and the experience of the project made available for others to learn from.
“There are lots of things we’re still working on, but there’s a huge amount of interest,” Robinson with LEVER said. “We have these products, and we can create more value for them in the communities that they are harvested, and that can create a more virtuous cycle between rural and urban parts of the country.”