Designing with American Hardwoods: A Sustainable, Versatile Material Choice

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WORKING WITH NATURE, INNOVATIVELY

Design professionals should know how to judge the sustainability of American hardwoods compared to other materials. When hardwoods are selected for a project, their natural properties and variations distinguish them from predictable, mass-produced materials. Architects who understand these natural processes and manufacturing methods often discover aesthetic and economic opportunities in the choices of species and lumber grades. Three green design principles can be helpful.

  • Work with nature in every respect.
  • Juxtapose hardwoods with other materials.
  • Accommodate hardwoods' natural properties during design and specifications.

Work with nature in every respect. Hardwood-savvy architects understand that some species are more abundant than others. As climate and soil vary, each combination of growing conditions favors a different palette of species. This holds true for various forests and regions across the U.S. Hackberry grows in Louisiana, for example, but not in Vermont; hard maple thrives in Wisconsin, but not in Georgia. This affects the commercial availability and relative affordability of each species. Making the most of this diversity, many architects first consider all the hardwoods native to a region before settling on a solution.

According to Chris Klehm, LEED AP, president of Clearview Construction Services in Pittsburgh, hardwood flooring was used for the 14,200-square-foot Eberly Family Learning Center at the Girl Scouts of Southwestern Pennsylvania's Camp Roy Weller, in Bruceton Mills, WV, where he was the general contractor. "Local West Virginia white oak was selected because it's durable," he says.

This hardwood choice also works effectively with the building's radiant heating system and its heat source, an energy-efficient geothermal system. The client, Denise Fowler of the Girl Scouts, says, "The Girl Scouts are extremely happy with the hardwood flooring over radiant heat. We have three geothermal boilers that make for efficient temperature control. This method significantly lowers our heating costs and promotes sustainability to our youth at the same time."

Klehm adds, "There are two reasons why I select hardwoods. First, they support the sustainable forestry efforts of farmers, as well as the process of creating oxygen for the atmosphere naturally, and second, they are beautiful. Few other products create value and beauty through the aging process."

Juxtapose with other materials. Peter Bohlin, FAIA, president of Bohlin Cywinski Jackson, Wilkes-Barre, PA, frequently juxtaposes multiple hardwood species, staining techniques, and contrasting materials. In a 2004 interview appearing in Material Matters, Bohlin says, "We've been using hardwoods for windows, particularly where we're wrapping [window frames] with copper." For the design and construction of a Utah mountain residence, he notes, "We've used maple or cherry for the basic wood frame that's visible on the inside, and a copper sheathing on the outside. Where we're at high altitudes... that is quite a sustainable strategy. Obviously, there's interplay between [the materials], but also it is really taking the same attitude to all of them, of going after those almost inevitable extensions of those materials and their natures... sort of expressing the spirit of the particular material."

London's Haberdashers' Hall, completed in 2002 and designed by Sir Michael Hopkins, of London-based Michael Hopkins and Partners, combines modern architecture with traditional materials and building skills to form a 21st century high-quality venue. Hopkins, who with his wife and partner, Patty Hopkins, won the 1994 Royal Institute of British Architects Royal Gold Medal, is known for his innovative approaches to construction and energy-efficient design. For Haberdasher's Hall, he chose stainless steel ties, rather than timber trusses, as bracing elements for the roof clad in American white oak. At each intersection of the lattice, four stainless steel shoes are glued to the wood, and bolted to a stainless steel node connecting to steel ties that brace the structure. The result is a light, open, elegant and unobstructed wood pattern.

Accommodate natural properties. Even when applications are innovative, hardwoods are far from experimental materials. They exhibit characteristic and predictable behavior in any application. All wood will reach equilibrium with its surroundings, as the internal moisture content, usually ranging from six to eight percent, adapts to the ambient relative humidity. Traditional techniques address this slight expansion and contraction when installing trim, molding, millwork, flooring or built-ins. On the job site, materials should be kept dry and indoors several days before installation, after the space is climate-controlled. This allows the wood to adjust to relative humidity levels.

Aldo Leopold was a powerful 20th century advocate for conservation and "intelligent consumption." In an article in American Forest magazine, "The Home Builder Conserves," he questioned "our universal insistence on clear hardwoods for furniture and interior woodwork.... Consider that the greater part of our enormous hardwood waste occurs in the process of trimming out knots. Is it too much to hope that fashion may some day lift the ban against them?"

Little has changed since Leopold made his plea in 1928. Hardwoods with character markings usually are seen only in rustic settings. The clear high-grade wood that makes up only a small part of the tree is the norm for flooring and architectural millwork in commercial or residential applications. Sustainable use of more of each tree remains a design challenge.

Few design professionals take advantage of the full range of natural visual effects possible with hardwoods.

 

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Originally published in Architectural Record.
Originally published in October 2005

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