Regional Sourcing - Helping the Carbon-neutral Balance

Regionally sourced hardwoods can make a real contribution to a project's sustainability. LEED grants green points for regional sourcing - those products extracted, processed and manufactured within 500 miles of the construction site. Local sourcing means that transportation costs are minimized, which saves money and petroleum resources, and creates less air pollution. Further, by purchasing local or regional American hardwood products, markets are created for hardwood trees, which in turn encourages landowners to manage their forestland in a sustainable way.

The LEED-Platinum, carbon-neutral Aldo Leopold Legacy Center is a prime example of effective regional sourcing. "Forest health was the foremost standard in planning and conducting the hardwood harvest at the Leopold Center. Most hardwoods came from a 20-acre oak woodland on the Leopold Memorial Reserve about two miles from the site," says Ecologist Steve Swenson of the Aldo Leopold Foundation, noting that the two major uses of American hardwoods in the Leopold Center were flooring and siding.

Architects specified some 8,000 board feet of exterior oak siding. The inch-thick boards are untreated. When exposed to the elements, oak typically weathers at a rate of about a quarter inch per century, according to the U.S. Forest Service's Forest Products Lab. Natural weathering has already begun to grey the exterior of the new building, reflecting the weathered look of the famous Leopold "shack." In addition, two porches were built using black locust for both the decking and railing. "Black locust is a non-native species in this part of the country, and it's naturally rot resistant, so we removed it from our native hardwood stand and eliminated a need for treated lumber," says Swenson.

Some 1,500 feet of cherry flooring was used in the formal meeting hall. The tongue-and-groove cherry flooring is 3/4-inch thick and 3/4-inches wide. "The cherry has the rich colors and wild whorls that the species is renowned for, and the rich shade of the cherry floor continues to deepen as it oxidizes," says Swenson, explaining that more durable white oak was used in the foyer, which is approximately 800 square feet. The tongue-and-groove oak flooring is 3/4-inch thick and 5 1/4-inches wide. "This oak has great grain, swirling around many knots, reminding us that these were smaller trees harvested to open up the forest canopy around older, larger oaks."

Local oak was harvested for the Drobish's traditional Pennsylvania barn. Photo courtesy of Hugh Lofting Timber Framing

 

The hardwoods also were used in tables made with white oak, bookcases and interior doors made with cherry, two counter tops made with thick slabs of cherry, which actually retain the curves of the trees, as well as Windsor chairs made from red maple and cherry, and exterior doors made from white oak. The diversity of uses made it possible to utilize the "whole tree," Swenson notes. The best, clearest, most stable, knot-free wood is on the outside of the log, in this case used for oak furniture, and cherry veneer, furniture, and flooring. Center material provided oak flooring and cherry for the core material of interior doors. To produce these materials and the finished products, the architects worked with a local sawmill, a local cabinet maker, and two local furniture makers.

Regional sourcing also was important for the Drobish family of Kennett Square, Pennsylvania, who wanted a traditional Pennsylvania barn. The project, which made ample use of oak from a local Pennsylvania forest, started with shop drawings in August 2005. The raising took about a month and was finished in January 2006 by Hugh Lofting Timber Framing, which crafts timber frame structures, including architectural trusses, great room additions, whole home timber frames, commercial inns, pavilions and barns. Downstairs, oak in the Drobish barn totaled 11,500 board feet; upstairs, an additional 15,741 board feet. "The Drobish family selected green oak for their barn for a number of reasons but, most importantly, because it is strong, long lasting, and of local provenance," said Hugh Lofting, who is one of a handful of woodworkers in the country responsible for the revival of the art of timber framing in the United States. Hugh studied timber framing methods across cultures, and his work is influenced by European, Asian and American techniques. "We have made a commitment to operate our company in a sustainable manner, and we encourage our clients to think about sustainable-building practices as they design their new homes and structures," adds Lofting.

Why Hardwood is Carbon Neutral

Environmentalists generally agree that hardwood is a carbon-neutral substance. While living, trees sequester and store carbon in their cellular structure. In fact, nearly 50 percent of the dry weight of a tree is carbon. Because hardwoods grow to be large trees, they lock in substantial amounts of carbon. However, as the tree becomes overly mature it start to release carbon, thus sustained harvesting and processing of mature trees sequesters carbon as finished wood products and start the sequestration of carbon in the form of new trees.

So conversion of wood into products such as structural beams, window frames, furniture, and doors, contributes to the long-term removal of carbon dioxide from the atmosphere, helping to reduce global warming. Long-term management of U.S. hardwood forests for sustainable timber production makes a significant contribution to carbon sequestration. Each year for the last 50 years, American hardwood forests stored around 110 million tons of carbon dioxide (excluding all harvested material). This direct contribution of America's hardwood forests to carbon sequestration excludes the carbon held in long-term storage as a component of American hardwood products. With useful lives spanning generations, furniture, flooring, cabinetry and trim crafted of American hardwoods act as an additional carbon store for many decades.

Once dead, wood left in the elements rots and becomes a fire hazard. Whether in a fireplace or decomposing in the forest, burning wood releases a significant amount of carbon dioxide - the greenhouse gas also released by fossil fuels - that is reabsorbed by growing trees. Hypothetically, this cycle can be repeated indefinitely. There is no similar claim that can be made for fossil fuel.