By Cindy Moffett. Photography courtesy of the Green Oak Project.
The Green Oak Project took seed a few years ago when forestry department Associate Professor Adam Taylor was showing some architecture students around a lumber mill.
“Do you see this stack of beautiful oak wood? They cut it up and make it into shipping pallets,” Taylor explained to the group. “Wouldn’t it be interesting if there was some way to use it structurally?”
But as is often the case with great ideas, there were solid reasons why the wood wasn’t being used for buildings. This particular type of wood is from the heart of the tree—what’s left after the rest is milled away. The problem lies in the large amount of water the living tree was storing there; hence the term green oak.
Drying wood before use helps stabilize it, but these large sections—four by six inches and up to sixteen feet long—require either years to dry outdoors or a large expenditure of energy to dry in a kiln—a process that also causes cracks, warps, and twists.
“It’s low-grade, low-quality wood,” Taylor said. “The number of knots and warping get much worse toward the center of the tree. On the other hand, it’s local, relatively low-cost, and has a very low impact to the environment, which I think is a big plus.”
Recently Taylor and Ted Shelton, associate professor in the School of Architecture, were able to pursue their idea. They assembled a team of four professors and nine students to secure a $15,000 Phase 1 grant from the Environmental Protection Agency’s People, Prosperity and the Planet (P3) Student Design Competition for Sustainability. The team expanded to include about twenty students, mostly from architecture but also from civil engineering, forestry, and environmental sciences.
During fall 2013, the students researched building ideas for green oak. Although similar work was being done in Europe, no one was using quite this product. “It was pure trial and error,” said architecture student Miranda Wright. “There were lots of times when we decided to look into, say, five different construction types. After research, we’d realize they were useless.”
“One of the technical challenges is building a structure that allows the wood to dry over the first two years,” Shelton said. “Often we put these structural members inside of walls, but we want to have some surfaces exposed to the air, which is not a typical way of detailing a building.”
“We were a little naïve at first because we thought we might be able to overpower the movement and force of the drying wood,” Shelton chuckled. “An important point in the process was realizing that we needed to accept what was going to happen and work with the nature of the material.”
The team finally decided to use a building method deeply rooted in the past. Four green oak timbers are joined into structural cross sections that take advantage of the wood’s longitudinal stability even as it dries. These preassembled “bents” are then lifted into place at the building site.
“It’s how barn raisings worked. They’d build a bent, which was basically an entire section of the barn, and push it up and connect it to the other ones that were already up. So we took a very traditional way of working and then adapted it for our purposes,” Shelton said.
One modification is in the joints. “In a barn we might have members that are twelve by twelve inches in diameter or even bigger, so there’s room for four or five of them to come together in the same joint,” Shelton said. “Our green oak is only four by six inches, so we had to simplify the idea so only two or three members come together at one joint.”
Once the team nailed down their basic concept, the architecture school’s third-year design students joined in. “They created concepts and buildings, which gave us the artistic side showing how beautiful this new construction can be,” Wright said. The resulting four-room house with a shed roof has a broad front porch and ample windows.
In spring 2014, the students began building a full-scale mockup of part of the house frame for their presentation in Washington, DC. “There were some scary points,” Wright said. “We had to build it at our fabrications laboratory, but later we would disassemble it, ship it to the competition, and build it once again. There were times when we stripped a screw, or tightened something that might not come untightened.” As the deadline neared, nights in the lab ran into the wee hours of the morning.
In April, two vans loaded with the mockup and other presentation materials headed to Washington to compete against teams from thirty-four other universities for the next round of EPA P3 funding. After three days of reconstructing the mockup, setting up models and drawings, and explaining their work, the team faced judgment day.
First, the project won the Student’s Choice award. Next came verdicts from the judges, a panel of experts from the American Association for the Advancement of Science. The hard work and late nights paid off when the Green Oak Project was named one of seven winners and awarded $90,000 in grant funding for further development.
Although Shelton is the project leader, he credits the students with the win. “The students really took this on and made it happen. It was a joy working with them because of their level of investment.”
In fall 2014, civil engineering students working with lecturer Jenny Retherford will tackle Green Oak as their senior design project. In the spring of 2015, Green Oak will return to the architecture students, and the goal is to have a finished house by the summer of 2016.
Turning their concept into a building holds many challenges, including negotiating codes and regulations to get permits for a new kind of building material. “But if we can walk down that path first and say yes, there’s a way—we’ve monitored it, we’ve measured it, we’ve shown that it’s viable, here it is—then we can pave the way for professionals to build with the same materials later,” Shelton said.
An inspiring precedent is UT’s New Norris House, which won the EPA contest in 2008 and went on to become one of the most sustainable houses in Tennessee while prompting changes in state building policies and applications.
“For us in the architecture school, any time we get to build is exciting,” Shelton said. “We get to go out there and translate our ideas into the physical world.”
Will the students be able to rescue stockpiles of this beautiful wood from the mundane fate of being crafted into shipping pallets? “We honestly don’t know,” Taylor said. “It’s a new idea and it’s local and sustainable. A progressive university and motivated young people are the right combination to explore whether or not this can work.”