On its own, wood is a renewable resource. But the list benefits continues to grow when it undergoes the process to become an engineered wood product.
Here, Peter Moonen of the Canadian Wood Council explains how engineered wood products can enhance the performance of a building, and what makes it a sustainable building material.
What is engineered wood and how is it made?
Engineered wood products (EWPs) have been around for generations. Plywood and glulaminated timber were two of the first commonly used EWPs. Structural EWPs are typically made of the same species of wood as solid wood construction products, but some, such as the oriented strand board, can be manufactured using non-structural species like aspen.
EWPs are made from solid wood, veneers, chips or individual fibres. They are then reconstituted using different resins and manufacturing processes. This produces products that perform better, or cost less, than the same dimension of solid wood.
There are a wide variety of EWPs for both structural (e.g. beams) and non-structural uses (e.g. flooring). Major structural products include parallel strand lumber and laminated veneer lumber. Some non-structural EWPs include hardboard or fibreboard, cladding and acoustic panels.
What are the benefits — structurally and environmentally — of using an engineered wood?
Wood’s foremost environmental benefit is its source — trees. Simply put, trees are solar-powered, carbon dioxide-sucking machines that store energy in a renewable building material.
EWPs tend to perform better as they have higher load-carrying abilities compared to solid wood of the same dimension. This is because EWPs have more uniform and predictable structural properties, as the usual deficiencies in the wood (like knots and cracks) are either removed or offset by the manufacturing process.
The resins used in structural products are stable in use and do not produce gas. Despite added energy needed to produce the product, as well as the resin and heat needed to cure and process it, EWPs sequester a lot of carbon. As most EWPs result in a higher density, carbon-intense wood products sequester equivalent carbon dioxide, resulting in a net negative carbon footprint.
Additionally, engineered products preserve or extend the use of the forest resource by using a higher percentage of fibre, which previously was burned or left to rot. The use of wood from residual sources, plantations and second-growth forests reduces the pressure to harvest more forest area.
There are concerns about using a wood as a primary material due to fire hazards. What should building developers know about engineered wood technology in regards to these concerns?
Designers and users need to understand both the strengths and weaknesses of every material they use.
As exposed, unprotected wood can burn, designers and builders must ensure certain construction practices are in place. But there is a distinction between construction fires and fires in occupied buildings.
During construction, buildings may not yet have fire protection or suppression systems in place. At this point, light frame wood buildings may be more susceptible to fire. However, national and provincial building codes ensure that all buildings, regardless of material meet the same safety and fire standards.
Heavy timber buildings, where the use of EWPs is common, react differently in fire. The mass of the product can make the building less susceptible and more predictable in a fire. As wood combusts, a char layer forms that reduces the amount of oxygen reaching the wood, thereby slowing the burn.
Wood’s natural thermal properties prevent heat from penetrating as rapidly as it can for other, denser materials. Heavy timber products and massive panels are difficult to burn. Ever tried to light a log with a match?
How can using engineered wood affect the sustainability of a building?
In addition to the benefits of wood as a renewable material, a building using EWPs sequesters carbon and can enhance the performance of the building, especially in energy use. Wood has natural thermal properties, which greatly reduce heat transfer. While many materials transmit heat easily, wood does not due to its structure. Imagine looking at a box of straws from the end — that is what wood looks like when magnified about 200 times. These hollow cellulose straws both reduce the wood’s density and provide insulation properties.
Peter Moonen is the sustainability co-ordinator for the Canadian Wood Council and has worked in the forest sector for almost 30 years. He provides design teams and regulators with technical support on wood products.