If Green Materials Fail, Have We Failed?
When I first read about the Chesapeake Bay Foundation case, I thought of Peter Moonen. Peter is the Leader of the Sustainable Building Coalition for the Canadian Wood Council. He has been extolling the virtues of wood and green buildings for years. Below, we discuss the benefits and pitfalls of parallam and other engineered wood products. If you are interested in a guest post or interview with Green Building Law Update, please contact Kirk Dryer.
Chris: I recently highlighted a lawsuit involving the use of Parallam. Would you consider Parallam a green product?
Peter Moonen: Yes, Chris, I would consider Parallam a greener product relative to it's functional alternatives, and for a number of reasons:
- Wood products are the only structural building material grown by the sun.
- Wood products are renewable, reusable, recyclable, organic, biodegradable and, while growing, remove carbon dioxide and emit oxygen as a byproduct – how cool is that?
- Parallam’s density means exceptional strength per volume and mass;
- Allows for use of material that would not generally be used for structural purposes (i.e. smaller veneer sheets and strips);
- Permits the production of large dimension structural products from smaller trees;
- Permits higher utilization of the forest resource. The recovery efficiency from logs and veneer varies with each mill. Some mills buy peeled veneer, which results in a 95+% plus efficiency, the 5% being used for energy. Others process round logs with a 60-65% recovery. This may reduce the recovery based on veneer, but produces other products as a result -- lumber, chips, sawdust, biomass. Very little of any tree is wasted.
- Zero off-gassing -- no urea formaldehyde resins are used;
- In the South and East US and Eastern Canada, it is usually made from second growth southern yellow pine or yellow poplar. In Western Canada, the wood for Parallam is second-growth Douglas fir.
- Plantation fibre is also suitable;
- Pre-cut sizes reduce waste on site;
- Like heavy timbers and glulam members, a large cross section of Parallam has proven to be resistant to fire.
- As a high density material, Parallam sequesters more carbon than is emitted during its production.
Chris: Does Parallam fail more often compared to standard wood products?
Peter Moonen: Every material has its strengths and its limitations. Designers, architects, engineers and other specifiers need to know what those capabilities and limitations are to ensure appropriate applications.
Like most wood products, parallel strand lumber is susceptible to the vagaries of nature. Water, intense sunlight, and blowing particles will take its toll on any exposed material – be it steel, concrete or wood – unless steps are taken to protect the material from those wearing forces.
When I talk to specifiers about materials I try to point out that no material is inherently bad or good, but how we use the product is what will determine its ability to endure. How materials are designed into a structure is critical to the success of that structure. No responsible designer is going to place untreated steel in proximity to salt water or use concrete in a structural application without rebar. Likewise, wood that is not protected from the elements will not last as long as it could.
Simply put, and aside from manufacturing defects, if a material fails it is generally because WE failed the material. We didn't understand the conditions under which the material should be used.
A colleague of mine does excellent work explaining durability of wood products. He explains there are principally three ways to make a wood product more durable:
- Durability by design (protecting the material from weathering factors by design),
- Durability by nature (choosing naturally durable species of wood for exterior use – like western red cedar) and
- Durability by treatment (or, as I say, durability out of a can) which can be expensive and needs to be done right using the right preservative and process for the use category. A suitable maintenance regime may also be important, especially for surface treatments.
Parallam, like all wood products, was never designed to be ‘bare-assed to the wind’. In fact Parallam, because of its structure, accommodates pressure treatment well, when made with wood species such as southern yellow pine, and effectively treated Parallam has been used in underwater conditions as piling. However, if untreated Parallam is placed in a position to fail, it will, as will any material put under the wrong conditions.
Chris: I have also read that Parallam is an engineered wood product. What are the benefits of engineered wood products?
Peter Moonen: In addition to the renewability and energy benefits of all wood products, the environmental benefits of most engineered wood products have a couple of additional benefits -- they preserve and they perform.
Engineered wood products extend the use of the forest resource by enabling a higher percentage of fibre use. The use of wood from residual sources, non-structural species, plantations and second growth forests reduces the pressure to harvest trees.
As well, engineered products tend to be have higher load carrying ability than solid wood of the same dimension. This is due to more uniform structural properties because any deficiencies in the material (knots, cracks, etc) are either removed or offset by the manufacturing process.
I would have to add that, despite the added embodied energy or resin and heat to cure and process Parallam, it still sequesters a lot of carbon. Most engineered wood products result in a higher density, and therefore carbon intense wood products sequester CO2e and result in a net negative carbon footprint. (CO2e stored minus CO2e to extract and produce)
Photo Credit: pnwra
The Foundation contracted with the architecture firm SmithGroup to design the project in 1998 and Clark Construction Group to build the project in 1999.
