A decision to use wood as the primary framing system in a building allows designers to minimize environmental impacts while achieving the lowest financial burden on owners. Wood is the only primary structural material that grows naturally and is renewable. Long before solar panels, wind turbines and geo-thermal heat exchangers made their way into our construction lexicon, wood was the original renewable resource. Haynes et al1 (2000) projected that by 2050, the demand for softwood products will increase by 38 percent, while softwood timber inventory (standing timber) will grow by 58 percent. Owners and their designers can therefore feel confident that the wood products they specify come from forests that are in abundant and sustainable supply.
Evaluating Environmental Performance
Historically, there have been few tools available to evaluate the environmental performance of buildings. For many years, there was only the US Green Building Council’s LEED rating system. However, during the past decade there has been a wave of new green building rating systems that compete with LEED and have a different view on how wood should be evaluated and rewarded for use in non-residential and residential construction. These include ASHRAE 189.1 Standard for the Design of High-Performance Green Buildings, the Green Building Assessment Protocol for Commercial Buildings (an approved American National Standard), and most recently, the International Green Construction Code (IGCC), completing a trio of robust rating systems that are readily available.
What these later systems have in common is recognition of the role life-cycle assessment (LCA) can play as a means to evaluate and select building materials. LCA provides a well-established, science-based approach that quantitatively measures key environmental impacts for specific products, assemblies and whole buildings. Typical environmental measures evaluated through LCA include embodied energy, global warming potential, and effects on land, air and water. In LCA, environmental measures are assessed over the life of the product, beginning with extraction, and continuing through manufacturing, transportation, installation, and end-of-life disposal or reuse. This is commonly referred to as “cradle to grave” analysis.
For the International Green Construction Code, an important option available to project developers and architects is compliance with a performance, rather than a prescriptive path in satisfying IGCC requirements, covering areas including site, materials, energy, water and indoor environment. The performance measurements for these categories are potentially applicable to almost every commercial building project, including additions and repairs. LCA is a great tool for measurement, as the option provides powerful insights into environmental impacts of project design and materials selection decisions.
If the LCA measurement pathway is not chosen, the material resource section of the IGCC requires that at least 55 percent of materials (based on mass, volume, or cost) be:
- used or recycled (at least 25 percent combined post-consumer and pre-consumer recovered content);
- and/or indigenous (locally sourced).
Referred to as the “55 percent rule,” the requirement–much like LCA–recognizes and credits sustainably sourced wood in building designs.
Environmental Product Declarations
An Environmental Product Declaration (EPD) is a document that provides, in a user-friendly format, the environmental impacts, energy usage and other information that results from a science-based LCA of a product. EPD development is guided by a set of international standards which call for initial creation of a product category rule (PCR) that defines the processes to be used when evaluating some or all of a product's life-cycle stages.
The North American wood products industry recently released industry-wide EPDs for structural products–softwood lumber, softwood plywood, oriented strand board, and glue-laminated timber. Development and verification of the EPDs was jointly sponsored by the American Wood Council and the Canadian Wood Council, referred to in the EPDs as the Declaration Holder. All four EPDs have been verified by UL Environment (ULE), as the “Program Operator.” The EPDs are available for viewing or download at AWC’s EPD website, which was launched May 7, 2013. Two additional EPDs for Laminated Veneer Lumber (LVL) and I-joists are scheduled for release by mid-2013.
Although none of the current green codes or standards recognize environmental product declarations, they are becoming more common for building products, as either company-product specific or representing industry averages broadly. In fact, a number of the green standards now under revision include recognition of EPDs in their current drafts.
Forest Certification and Carbon Neutrality
Further, wood is the only primary structural material having third-party certification programs in place to verify that products originate from a sustainably-managed resource. Where LEED awards points for wood certified by only one forest certification program, the other building rating systems (such as the IGCC) recognize the three leading programs commonly used in North America–Sustainable Forestry Initiative (SFI), American Tree Farm System (ATFS), Forest Stewardship Council (FSC) and Canadian Standards Association (CSA). At the end of 2011, SFI had 196 million acres of forests certified in North America2, the largest of any of the certification systems. Building rating systems that reward all credible forest certification systems are ensuring that future generations will inherit healthy, sustainable and valued forests.
Further, responsible forest management–and the resulting forest products–play a critical role in helping to tackle climate change and reduce greenhouse gases. Wood offers the desirable characteristic of storing or sequestering carbon, which results from trees absorbing atmospheric carbon dioxide in the growing process while releasing oxygen to the air through photosynthesis. Using wood products that store carbon and responsibly managing forests in a way that balances harvesting and replanting can minimize our carbon footprint over the long term.
The introduction of newer and more robust green building rating systems such as the International Green Construction Code has created the opportunity to recognize the real environmental benefits of building with wood. Wood is a renewable and responsible resource that helps reduce the environmental footprint of construction while providing a complete building solution. Accordingly, wood buildings offer safe, durable and affordable solutions for your next facility.
1 Projections of The U.S. Timber Supply And Demand Situation To 2050-Draft Findings From The USDA Forest Service 2000 RPA Timber Assessment. Richard Haynes et al
2 SFI 2012 Progress Report