Studies in sustainability

Wood is demonstrating its green credentials by example

fune cAN BE No DouBr today that I. the sustainability movement and green building in pariicular are here to stay. Green building criteria are now codified in numerous building codes and national standards, and increasing numbers of local jurisdictions are adopting green building requirements.

Nor can there remain much doubt-given both the objective dara and a growing body of real world case studies-that wood, and engineered wood in particular, makes an important contribution to the worthy goals of sustainability and green building.

The common sense and scientific support for the green credentials of wood is substantial, long-standing, and well documented.

. Wood's strongest suit is perhaps its most obvious-wood is the only naturally renewable building material. That fact is made all the more compelling by the corollary truth, contrary to common misperception, that forest growth in North America has exceeded forest harvest for decades.

Advancements in wood product manufacturing technology continue to improve wood's sustainability quotient. The industrial output per unit of wood input has increased 40Vo over

By Jack Merry

the past half century. That trend has accelerated with the advent, acceptance and wide use in recent years of modern engineered wood products, which use more of the available resource with less waste and can be produced from fast-growing, underutilized and less expensive wood species.

. Wood products are made from forest resources harvested under a number of internationally recognized certification programs, including the Forest Stewardship Council, Sustainable Forestry Initiative, Canadian Standards Association, and American Tree Farm System. The programs assure that wood fiber resources are sustainably grown and harvested.

Life cycle assessment (LCA) research shows that by a number of "cradle to grave" sustainability measures, wood is substantially more environmentally friendly than alternative construction materials. Wood products, for example, make up 47Vo of all industrial raw materials manufactured in the U.S., yet consume only 4Va of the total energy needed to manufacture all industrial raw materials. Wood products are recyclable, a fact of increasing importance and relevance to carbon sequestering efforts.

Wood can be and today is easily and commonly incorporated into residential and nonresidential buildine designs recognized under a number oT green building rating systems.

Despite all of the above arguments, uninformed bias against the green merits of wood still exists in some quarters. But for skeptics looking for proof, they need not look far.

Take the Environmental Nature Center in Newport Beach, Ca., completed in 2008 for a nonprofit of the same name that serves as its community's foremost authority on ecological responsibility, sustainable practices, and environmental education. The 8,500-sq. ft. mixed use complex contains administrative offices, classrooms, a museum, and gift shop-all protected and aesthetically enhanced by an exposed wood roof system and wood-frame shear walls.

The complex-a main building housing public areas separated from an administrative building by a breezeway-uses Structural I APA Rated exposed plywood roof sheathing, dimensional lumber subpurlins, glulam purlins, and wood l-joist roof framing. Wood shear walls employ dimensional lumber studs and plywood sheathing.

Budget considerations were a factor in many of the design features. The exposed wood roof framing reduced the need for traditional ceiling materials and finishes. In some areas, partial-height wood wall studs also were purposely left exposed to showcase the structure's dedication to design efficiency and low environmental impact. This not only helped lower initial construction costs, but also minimizes ongoing interior maintenance expenses.

The many sustainable features of the center, including the structural wood envelope, are themselves now a highlight of the ENC's educational programming and are identified in signage placed throughout the structure. One exhibit notes the structure's LEED Platinum designation, the highest level of LEED certification and a first in the county. The project earned 55 out of 69 possible LEED certification points, and met or exceeded standards in six LEED categories.

In Annapolis, Md., the Chesapeake Bay Foundation also used wood in pursuit of sustainability goals for its Philip Menill Environmental Center. The foundation, a nonprofit devoted to protecting Chesapeake Bay, wanted a design that supported its sustainability message by minimizing the impact on surrounding habitats.

"Our philosophy is that the greenest building is the least amount of building we truly need, built with the fewest number of materials," said foundation president William Baker.

To that end, a variety of structural- ly efficient engineered wood products was used-plywood subfloors, parallel strand lumber, wood I-joist framing, and structural insulated panels faced on both sides with OSB. Much of the wood is left exposed to both capitalize on the aesthetic qualities of the material and reinforce the "less is more" sustainability message.

Completed in 2000, the 30,000-sq. ft., two-story Philip Menill Environmental Center was the first to receive the LEED Platinum rating and continues today to be recognized as one of the world's greenest buildings. It also was the second highest rated building among a survey of 20000 occupants of 150 buildings for overall building satisfaction, including aesthetics, acoustics, light and air quality.

"The facility is a major recruitment tool," said Mary Tod Winchester, the foundation's v.p. "It has been a mag- net for the audiences whose building projects we want to influence."

Schools, too, are a natural end-use market for wood design because when completed they can themselves be used as dramatic case histories and effective teaching tools for broadening understanding of the sustainability attributes of wood building materials. Gunter Primary School in Gunter, Tx., serves as one such example.

Completed in 2O07 , the 60,000-sq. ft. facility includes classrooms, a computer lab, kitchen, cafeteria, gym and offices. The school's unique design employs wood in both exposed and hidden structural applications. APA Rated wood structural panel sheathing was used to enclose the building's walls. Wood I-joists were used for rafters in combination with glulam timber support beams. And a laminated lumber decking with T&G edges was used in combination APA Rated plywood sheathing for diaphragm strengthening in the roof system.

"I've been in business for 35 years, and I enjoy doing projects with wood," said project superintendent Donald Hampton. "I've put up large buildings before, but with the overall building height and length of spans, it (Gunter Primary) was different. One of the glulam beams is l2 inches wide by 7 ft. deep and 82 ft. long."

Although the project was not certified under a green building program, its abundant use of wood satisfies sustainability goals by several measuresuse of energy efficient materials, quality of indoor environment, durability, low maintenance, and availability of materials regionally produced to lower transport energy consumption.

Gray Middle School in Tacoma, Wa., underscores another way to achieve sustainability through the use of wood-recycled material. In this case, the product was glulam beamsmore than 200 of them-that were salvaged from an old high school that formerly occupied the site. The beams support the primary roof structure for a new commons area, science rooms, and central gallery.

The recyclability of wood is a material attribute likely to assume greater importance as the nation's inventory of residential and nonresidential buildings ages and is replaced. Products that were once relegated to the waste stream are increasingly viewed as viable, valuable elements of sustainable design strategies.

The sustainabilitv of wood con-