GUEST COLUMN: Earn Green Points by Building Multifamily with Wood

By David Helmers, iLevel by WeyerhaeuserFor economic and structural reasons, wood has long been the preferred building material for low-rise multi-family housing. Now, with sustainability an increasingly important factor in construction, multi-family builders are also choosing wood for its environmental benefits.  Under the National Association of Home Builder’s (NAHB) National Green Building Standard™, builders can use certified lumber, engineered wood products (EWPs) and advanced wood framing methods to earn points toward a green building rating.Green attributes of woodWood offers multiple environmental advantages, including that it comes from a renewable, natural resource that helps reduce carbon dioxide (CO2) in the atmosphere. As trees grow, they absorb large amounts of CO2 during photosynthesis and when harvested, the carbon remains stored in the wood products indefinitely.Unlike other structural framing materials, wood is also a good insulator. According to the Canadian Wood Council, steel conducts heat much faster than wood, and this leads to higher energy usage and the need for additional insulation above what is required for wood framing. Wood also requires less energy to manufacture, transport, construct and maintain than steel or concrete, helping to reduce fossil fuel consumption and greenhouse gas emissions.EWPs further expand wood’s environmental advantages by allowing for efficient use of trees. The manufacturing processes use virtually every portion of every log to produce strong and consistent framing members. EWPs can also be designed to do more work with fewer materials. For example, wood I-joists have a structurally efficient shape that can carry loads using less material than a rectangular joist.It is important to know if lumber and engineered wood products you are using came from sustainably managed forests. Certification by independent third parties, such as the Sustainable Forestry Initiative (SFI), provides the assurance that the wood was grown and harvested in environmentally responsible ways.  Check for a certification label or ask the dealer for more information about certified products.  Taking green construction a step further, by using ready-to-install materials—from pre-cut, bundled and labeled products to pre-built framing components—builders can optimize the use of both lumber and EWPs, while reducing jobsite wood waste and construction cycle time. Earning points in the National Green Building StandardThe National Green Building Standard defines green building for single and multifamily homes, residential remodeling projects and site development projects, while still allowing for the flexibility required for regionally appropriate best green practices. To make it easier for builders to identify qualified products, the NAHB Research Center recently introduced its new “Green Approved” Products Seal of Approval. The mark is intended to provide third-party evidence that building products meet specific scoring criteria.The National Green Building Standard consists of six areas that builders can earn points within:• Energy efficiency• Water efficiency• Resource efficiency• Lot design, preparation and development• Indoor environmental quality• Building owner educationOf these areas, wood structural framing can earn credit under resource efficiency and indoor environmental quality.  Under resource efficiency, certified lumber and EWPs can potentially earn points in the bio-based product category. The standard recognizes certified wood products from a number of credible programs, including SFI. Companies with qualifying environmental management systems can also potentially earn points.Due to its low embodied energy, wood framing can potentially earn points for materials from renewable energy sources, resource efficient materials (notably engineered wood products), and life cycle analysis. Depending on the risk level of termite infestation, choosing treated lumber or EWPs for structural frame components can earn points for the termite-resistant materials category.The various types of ready-to-install framing can contribute to several categories, including optimized materials use, reduced material cuts and waste, detailed framing plans and on-site cut lists, pre-cut or pre-assembled components, and construction waste management.Additionally, using materials that originate within 500 miles of the construction site is eligible for points under the regional materials category.Under indoor environmental quality, given the very low formaldehyde emissions from EWPs, oriented strand board, laminated strand lumber and parallel strand lumber can fit in the low emitting materials category.David Helmers is a structural frame expert for iLevel by Weyerhaeuser