Advertising supplement provided by The Hardwood Council
Each hardwood board has a unique life story. During the approximately 60 years it takes for an American hardwood to mature, each tree develops a unique grain pattern and texture. Even boards from the same hardwood tree will show significant variation in color.
Wood Anatomy and Characteristics
The tree's newest wood, closest to the bark, is known as sapwood; it is lighter in color and without knots or other character markings. This is the highest grade and most expensive lumber. The oldest wood toward the center of the tree is the heartwood. The heartwood is more character-marked than clear wood; it is darker and denser. As the tree grows, knots mark the points where branches joined the trunk.
Both clear and character-marked wood have value in the built environment, and eco-effective designs make fullest use of the resource and reflect the tree's entire history. By specifying only wood that is free of knots and other visible marks, architects can either miss opportunities for rich visual qualities or ways to reduce costs.
Grain pattern or figure is created when the log is sawn into lumber; it not only affects aesthetics and budget, but also is an important consideration in green and sustainable design.
In flat- or plain-sawn hardwood boards, growth rings are parallel to the board's surface and create the distinctive flame-shaped, arch or cathedral grain pattern. Flat-sawing, representing 95 percent of all commercial U.S. hardwood lumber, produces the most lumber and the widest cuts at the lowest cost.
In quarter-sawn lumber, the growth rings are perpendicular to the board's broad face, producing a vertical and uniform grain pattern. Quarter-sawing yields fewer, narrower boards per log than flat-sawing, adding to the cost. Structurally, quarter-sawn pieces have good dimensional stability, but not necessarily better than properly kiln-dried flat-sawn lumber. Quarter-sawn boards are popular for decorative applications such as cabinet faces or wainscoting and many species display a striking ray-like pattern.
Rift-sawing at a 30-degree or greater angle to the growth rings produces narrow boards with accentuated vertical or “straight” grain patterns. With their straight grain, quarter-sawn and rift-sawn flooring expand and contract vertically, as opposed to flat-sawn boards which expand horizontally. Nonetheless, all hardwood products will expand and contract as they reach balance with the relative humidity of their surroundings.
Combinations of Woods
Hardwood species and grain patterns are often used in combination to impressive visual effect.
In the Lewis and Clark Building, BNIM used solid quarter-sawn ash to build the fixed window units and the decorative trim. All office doors in the facility are made of solid ash, while locally-sourced ash veneer was applied over a non-formaldehyde substrate in cabinetry, wall panel and casework applications.
“Since we used two species of oak for flooring applications, the ash really complemented the aesthetics of the other materials that were specified,” notes Hickson. “We were especially excited about the ash wall panels because it creates a much different atmosphere than if they were made from drywall.”
The Future of Environmental Design
In coming years, it is likely that evidence-based and patient- or occupant-centered design will gain momentum and inform the practice of green and healthy design. Across the board, architects and clients are moving toward healthy and green design in buildings of all types.
Architect Paula Baker-Laporte notes, “There is still some confusion surrounding the topic of healthy design, but I definitely see a merger with green design occurring. Healthy design is clearly registering on people’s radar. When I first started looking into the topic, it was really only for people with chemical sensitivities. What I have seen recently is a tremendous shift from sick people to healthy people wanting to remain healthy.”
Anjali Joseph, of the Center for Health Design, observes, “In a health care environment that’s well-designed and attractive, if there are green elements and natural materials, it’s very difficult to say if it’s attractive because of the biophilia–attraction toward nature–or if it’s because it’s a well-designed environment.” She predicts that in coming years, more researchers will be exploring the benefits of natural materials in the built environment because, “We’re all in the early stages of learning about these issues.”