Wood: The Material of choice

November 2012 » Features » WOOD-BUILDING SOLUTIONS
New solutions with wood are more sustainable, affordable, better looking and withstand hazardous conditions better than alternative materials.
Christina M. Zweig
The Kebony Boat House in Oslo, Norway, uses a new variety of wood that tolerates harsh climates and acquires an attractive patina on exposure to the sun and natural elements.

The aesthetic value and intrinsic benefits of wood are numerous. Architects and engineers are using wood for structural purposes on buildings of all types – from healthcare facilities to schools, from residences to bridges.

Research has concluded that the use of wood helps reduce the environmental impact of buildings. Wood lowers a building's carbon footprint by continuing to store carbon absorbed during the tree's growing cycle, keeping it out of the atmosphere for the lifetime of the building. Wood processing is less fossil fuel-intensive than the manufacturing of steel and concrete, which means fewer greenhouse gas emissions. According to the APA—€”The Engineered Wood Association, wood also has inherent characteristics that make it an ideal material for construction in areas prone to earthquakes and hurricanes. Weight and flexibility allow a wood-framed building to absorb and resist these forces.

Innovative roof
A recent WoodWorks case study details a 6,000-square-foot rooftop addition onto a 1950s-era brick and concrete warehouse in Culver City, Calif., that took wood to new heights with curved and beveled glulam beams forming an innovative roof.

"We made our decision for 3555 Hayden based on what was the best, most economical way to create this design. Wood was the clear answer," said Dolan Daggett, project director for Eric Owen Moss Architects, the project architect. Englekirk Partners Consulting Structural Engineers, Inc. were the structural engineers.

Daggett said the firm never considered the option to use steel. Design work for this structure began in 2004. The use of wood was essential to create the undulating roofline design.

"From a design perspective, we wanted the roof to do more for this building. In order to exaggerate the form and construct a more exuberant design element, we needed a pliable, shapeable structural material," Daggett said.

The architects also wanted to have exposed wood elements on the interior of the space and wood was touted for having the unique ability to follow the shape of the building and a "warm" look and feel.

The architect formed the complex roof structure with 22 glulam beams, ranging in length from 16 to 52 feet. The manufacturer finished the Douglas fir beams, sized from 5-1/8 to 6-3/4 inches wide and 9 to 30 inches deep, to an architectural appearance. The arched beams were manufactured with specific curvatures, then a computer numerically controlled machine cut a continuous bevel on the beam's top edge to form the compound slopes.

"The roof structure went together like a kit of parts, pieced together at the job site," Daggett said in the WoodWorks case study. "All fabrication was done before materials arrived at the job site, and our contractor, Samitaur Constructs, just had to put it together."

Wood offered other benefits and met the required structural properties. The Hayden project was built in compliance with 2001 Title 24, Part 2 of the California Building Code, and was additionally designed to meet the requirements of a 70 mph design wind speed with exposure B in seismic zone 4. The project went on to win the WoodWorks California 2012 Commercial Wood Design Award and the AIACC Achievement Award, 2008.

Wooden schools
Another WoodWorks case study detailed how the design team for a new high school saved $2.7 million with the choice to use wood framing – and created a beautiful and functional space.

Interior and exterior views of the Kebony Boat House.

El Dorado High School was one of the first schools in Arkansas to make extensive use of wood following a change in state policy that had previously prohibited wood in school construction. In 2008, the Arkansas School Facilities Manual was modified to reflect the International Building Code, which allows the use of wood in a wide range of building types. Technical information provided by the American Wood Council, APA and Anthony Forest Products, which demonstrated wood's safety and performance capabilities, were large factors in the decision.

The new 322,500-square-foot high school was finished in 2011, landing on its target price of $134/square foot. During the design phase, project architects, CADM Architecture, Inc. worked with construction managers Baldwin & Shell to evaluate various systems.

"Originally, the project was designed in steel and masonry, which is common for a building of this size," said J. Richard Brown, P.E., principal engineer with the project's structural engineering firm, Engineering Consultants, Inc. in Little Rock. "But the budget was too high. So our response was to look at other framing types. That's where we found considerable savings."

The facility was built as Type III-A construction, fully sprinklered. It has one-hour fire ratings for the structural frame, interior bearing walls, second floor construction and roof construction. Because of the building's size, the design team specified fire-retardant-treated wood studs and plywood for the exterior walls. At the time it was built, El Dorado's new high school was the largest wood-frame school in Arkansas.

Always new
New things are being done with the same old material. Kebony AS, a Norwegian technology company, has patented a process called "kebonization" that enhances wood properties so it becomes harder and more stable, with improved durability, by using a bio-based liquid, which enhances the cell structure.

The company was the winner of the British Best Business Award for Innovation in 2012.

Kebony's patented modification methods are the result of many years of research and development in Norway, Sweden and Canada. They are also based on collaborations with universities and institutes in Germany, the Netherlands, the U.S. and South Africa, including the Norwegian Institute of Wood Technology, the Norwegian Forest and Landscape Institute, the SP Technical Research Institute of Sweden, SHR Timber Research in the Netherlands, and the University of New Brunswick and Woodtech in Canada.

Several wood types are suitable for kebonization. Currently Kebony products are produced from various pines and maple. This new variety of wood tolerates harsh climates and acquires an attractive patina on exposure to the sun and natural elements. Its areas of application range from roofs, wall claddings to floors, furniture, kitchens, even docks and yacht decking.

A recent project featuring the technology is the Kebony Boat House, a traditional yet eye-catching landmark in the heart of Oslo Harbour.

As part of Kebony's ongoing partnership with TreStykker 2012, an independent workshop involving students from three of Norway's most prestigious architecture and design schools, the Kebony Boat House is the latest of three high-profile collaborative projects between the two parties.

Kebony's impressive durability and long lifespan in harsh climates made this wood material the right choice for the new harbor-side landmark.

In recognition of its revolutionary approach, Kebony was acknowledged as one of the world's most promising clean technology companies in the highly competitive Global Cleantech 100 in 2010 and 2011.

Christina M. Zweig is a contributing editor. She can be contacted at christinaz@zweigwhite.com.

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