Framing Lumber from Building Removal: How Do We Best Utilize This Untapped Structural Resource?
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Framing Lumber from building removal: How Do We best Utilize this Untapped structural resource? Authors: robert H. Falk steven cramer James Evans (corresponding author) Professor Mathematical Statistician Research Engineer Department of Civil and USDA Forest Products Laboratory Advanced Housing Research Center Environmental Engineering Madison, WI 53726-2398 USDA Forest Products Laboratory University of Wisconsin [email protected] Madison, WI 53726-2398 Madison, WI 53706 [email protected] [email protected] AbstrAct Compared with other construction materials, wood products are environmentally attractive because they sequester carbon, are renewable, and are low in embodied energy. Lumber salvaged from building removal possesses these same qualities but with additional environmental attributes. In spite of the environmental attractiveness of reclaimed lumber, its widespread acceptance is hampered because it is not formally recognized in our grading or engineering design standards. This causes confusion for consumers, builders, and building officials, both in the marketplace as well as at the jobsite. In this article, possible alternatives for recognizing and accommodating reclaimed lumber in lumber grading and wood engineering design standards are provided. 492 FALK ET AL. INTRODUCTION to reproduce the product new, makes reclaimed The past decade has seen tremendous growth in lumber a leading contender for the greenest of green building practices, and the building design green building materials. and construction industries are paying more In this article, we will discuss the potential attention to reducing a building’s energy and water for reusing lumber in construction, some of the usage, reducing a building’s waste and carbon current barriers to wide-scale reuse, the state footprint, and specifying building materials that of engineering research to quantify its residual are not only sustainable, but that have the lowest properties, and some suggestions on how to move Framing Lumber from building removal: environmental impact. forward to broaden acceptance of reclaimed To this end, the green building community lumber in the marketplace. How Do We best Utilize this Untapped has stressed the use of newly manufactured recycled STATE OF LUMBER REUSE TODAY content building materials or exotic “green” The salvage and reuse of lumber and timber materials (e.g., bamboo flooring, wheatstraw is in many ways nothing new, and as long as structural resource? doors, hempcrete) in building construction wood buildings have been built, some amount projects. Until recently, relatively little attention of salvage has occurred. Some believe that more has been given to reusing the millions of tons building materials were salvaged before World of building materials we already have; that is, War II, and that the associated development of the components and materials salvageable from large construction machinery during and after building removal that would otherwise end up the war allowed rapid mechanical removal of in the landfill. This is surprising because, as the buildings (M. Taubert, Duluth Timber Company, three “R’s” of wise material use (Reduce, Reuse, personal communication, 2000). Also, the Recycle) state, reusing material is higher up the Authors: development of safety regulations that distanced hierarchical ladder than recycling material (or a worker from the materials in a building and a using a material with recycled content). Whereas trend of compressing the time allowed to remove reusing some building materials and components a building and prepare a site for redevelopment, is impractical because they are difficult to take have resulted in a disincentive to salvage building apart and reinstall (such as a concrete beam in a materials. cast-in-place concrete building), other materials, As early as the 1970s, the timber framing robert H. Falk steven cramer James Evans such as framing lumber, in most cases can be industry recognized the value of salvaged wood (corresponding author) Professor Mathematical Statistician easily salvaged and reused. Research Engineer Department of Civil and USDA Forest Products Laboratory and has used larger timbers reclaimed from Advanced Housing Research Center Environmental Engineering Madison, WI 53726-2398 Wood possesses many positive industrial structures for the exposed framing of USDA Forest Products Laboratory University of Wisconsin [email protected] environmental attributes, including renewability, high-end new construction. Framers value not only Madison, WI 53726-2398 Madison, WI 53706 low embodied energy, and the ability to sequester the dry and stable nature of these larger members, [email protected] [email protected] carbon (Falk 2009). Life-cycle analyses, especially but also their unique character, especially the aged those related to the efforts of the Consortium patina and old-growth qualities (see, for example, AbstrAct for Research on Renewable Industrial Materials www.tfguild.org). Compared with other construction materials, wood products are environmentally (CORRIM 2010), have shown the advantage More recently, interest in salvaging attractive because they sequester carbon, are renewable, and are low in embodied wood building materials have over other common and reusing smaller dimension (2-by) framing energy. Lumber salvaged from building removal possesses these same qualities but building materials (e.g., steel, concrete) from an lumber found in most single-family house with additional environmental attributes. In spite of the environmental attractiveness embodied energy and carbon footprint standpoint construction has been growing. Reused building of reclaimed lumber, its widespread acceptance is hampered because it is not formally (Lippke et al. 2004, Perez-Garcia et al. 2005). material businesses have grown rapidly over recognized in our grading or engineering design standards. This causes confusion Recent research points to the added the last 20 years, and many of these businesses for consumers, builders, and building officials, both in the marketplace as well as at environmental benefits of reusing lumber and sell lumber reclaimed from the deconstruction the jobsite. In this article, possible alternatives for recognizing and accommodating its positive impact on reducing carbon footprint (or dismantlement) of wood-framed buildings. reclaimed lumber in lumber grading and wood engineering design standards are (Napier et al. 2007, Bergman et al. 2010). Reusing Habitat for Humanity (HfH) ReStores, which provided. wood materials, and avoiding the upstream energy sell donated and salvaged building materials, FOREST PRODUCTS JOURNAL Vol. 62, No. 7/8 493 now number over 700 in the United States and marketed. For discussion purposes, we will loosely This lack of definition can result in uncer- not. Several of the agencies that do not currently Canada. The first ReStore opened about 20 years define these two groups as “larger timbers” and tainty, especially at the building site, where ap- allow reuse expressed that if definitive standards ago, in 1992. Several hundred non-HfH reused “2-by lumber.” Although grading rules technically proval for reuse of lumber is inconsistently grant- and guidance were available, they would consider building material businesses have also opened in define “timbers” as anything 5 inches and larger in ed. On one hand, a building inspector may judge allowing reuse. the same time period (Building Materials Reuse least dimension, for purposes of this discussion we that a piece of reclaimed lumber is acceptable for WILL RECLAIMED 2-BY LUMBER Association, personal communication, 2012). will define “larger timbers” as anything larger than reuse, justifying approval on the fact that it func- PERFORM STRUCTURALLY? a 2 by 12, the largest solid sawn wood member tioned well in its previous structural application. RESOURCE POTENTIAL A logical question to ask before considering the typically used in single-family house construction. Another inspector, however, may disallow reuse A significant amount of lumber is potentially avail- altogether because there is no guidance available recognition of reclaimed lumber for reuse in con- Larger timbers are typically salvaged from able for future reuse. Since the turn of the 20th cen- that specifically allows reuse. Unfortunately, nei- struction is “Will the reclaimed lumber perform 12 larger industrial buildings and usually end up in tury, more than 3 trillion (3 × 10 ) board feet (7 × ther scenario is ideal, because the first relies to a adequately when reused in a structural applica- 9 3 one of two markets, depending on size and spe- 10 m ) of lumber and timber have been sawn in certain extent on blind faith with no quality control tion?” cies—the timber framing market or the remanufac- the United States, much of it still residing in ex- to assure product performance, and the second re- The authors (with others) attempted to an- tured wood flooring market. The timber framing isting structures (Steer 1948, Howard 2001). As jects out of hand the use of a viable resource be- swer this question by initiating a testing program industry has relied on job-specific grading and en- the building infrastructure in North America ages, cause no guidance is available. to evaluate the residual engineering properties of there will be increasing opportunities to reclaim gineering approval of the timbers used to meet lo- Also, lumber grading agencies in the Unit- 2-by lumber salvaged from different buildings in materials from building removal.