How much do things seen in LEED (recycled content, local sourcing, etc.) matter?
Author: Kelly Roberts; Contributors: Martha VanGeem, John Anderson, Rebecca Jones
Author: Kelly Roberts; Contributors: Martha VanGeem, John Anderson, Rebecca Jones
In the current version of LEED, LEED 2009, the two main credits that structural engineers tend to focus on are the regional and recycled content material credits. These are also the two credits in the Materials and Resources category that are overwhelmingly most often pursued and won, as demonstrated by the bar graph below. However, recycled content and regional content in LEED 2009 and previous versions are single attribute criteria that do not take into account a full life-cycle assessment (LCA) of materials and can therefore sometimes misrepresent the actual environmental impact of the project materials.
Figure 1: Breakdown of LEED Materials and resources points awarded (The Institution of Structural Engineers 2012)
Before looking further into the recycled and regional content credits, it is important to recognize that there are some credits within LEED 2009 that do better at considering life-cycle impacts. MR credit 1, Building Reuse, awards points to project teams that reuse existing buildings and nonstructural elements. Although not always recognized as such, this credit may have one of the largest embodied environmental benefits of all of the material credits. Humbert et al (2007) conclude: “The initial credits of materials & resources (aiming at reusing the structure of the building) provide high benefits, whereas the rest have low benefits.” Unfortunately this is one of least pursued credits within the Materials and Resources category. However, since an actual life-cycle assessment is not part of LEED 2009, any quantifiable environmental benefits for each credit are generally unknown to project teams.
The recycled content credit, MR Credit 4, states, “The recycled content value of a material assembly is determined by weight. The recycled fraction of the assembly is then multiplied by the cost of assembly to determine the recycled content value.” Since the focus of this credit is on cost, project teams can focus on purchasing big ticket items with high levels of recycled content in order to achieve the credit. However, as Scheuer and Keoleian (2013) have noted, this approach does not accurately reflect the material environmental impact nor ensure the greatest environmental benefit to the project. In fact, in many cases, this credit can be achieved by only using standard construction materials and techniques. For example, structural steel is a commonly used and highly recycled material. For many commercial buildings, both points for this credit can be achieved by considering the recycled content value of the steel alone since steel is both a high cost (because the high quantity used) and highly recycled (Scheuer and Keoleian 2013). In addition, some recycled materials, such as ceramic tile, may have a greater environmental impact than their virgin counterparts (Scheuer and Keoleian 2013).
In some cases, specifying a certain recycled content coupled with a failure to appropriately weigh accurate environmental impacts can result in unintended negative impacts. Anderson and Silman (2009) point out that since there are many variables in environmental impacts, proper metrics and weighting should be used in lieu of simplifications. For example, in the case of specifying high recycled steel content, the authors point out, “The mature scrap market for steel, a highly valued material, already results in recycling rates of 85% for the construction industry. The specification of a minimum recycled content, or completely recycled materials, causes rerouting of materials that would have already been recycled, thus creating additional environmental burdens associated with transportation”.
The regional content credit, MR Credit 5, states, “use building materials or products that have been extracted, harvested or recovered, as well as manufactured, within 500 miles of the project site for a minimum 10% or 20%, based on cost, of the total materials value. Since this credit is again, based on cost, there are similar environmental pitfalls with this credit as with the recycled content credit. The credit can promote a false impression that materials of low mass that have been chosen due to their proximity to the project site have a smaller environmental impact which, within the boundaries of a case study by Scheuer and Keoleian (2013), does not appear to have merit. This credit largely addresses the transportation portion of the material life cycle. Since building construction requires large volumes of materials to be delivered to a single project site, the environmental impact due to transportation and the consumption of fossil fuels can be significant (Scheuer and Keoleian 2013) . While this credit intends to promote local economies, since the 500 mile radius can extend over several municipalities, states and regions, it is questionable whether the credit actually achieves this goal.
The proposed next version of LEED, LEED v4, is scheduled for member ballot in the summer of 2013. In its current form, the Materials and Resources section of LEED v4 will see a major overhaul with several additions and changes to the credits. As proposed, the new Materials and Resources section will focus on supporting a life-cycle approach to material selection, at both the whole-building and the product level. In previous versions of LEED, the Materials and Resources section focused on single attributes of materials such as regional sourcing or recycled content. With this move toward incorporating life-cycle assessments for the whole building and products, LEED is attempting to take a more holistic approach to determining the environmental impact of materials and resources.
The first Materials and Resources credit in the current LEED v4 draft, “MRc1: Building life-cycle impact reduction”, is intended to “encourage adaptive reuse and optimize the environmental performance of products and materials” and aims to look at the life-cycle impact at the whole-building level. This credit rewards the most points to project teams that are able to reuse or renovate an existing building with an emphasis on reusing a historic, abandoned, or blighted building. Points are also awarded to project teams that perform a whole-building life-cycle assessment and can demonstrate a 10% reduction across various environmental impact measures versus a reference building.
The next three credits included in the LEED v4 Materials and Resources section are different variations of “Building product disclosure and optimization”. The first intent of all of these credits is to “encourage the use of products and materials for which life-cycle information is available and that have environmentally, economically, and socially preferable life-cycle impacts”. The first of these credits, MRc2, focuses on environmental product declarations (EPDs) and aims to encourage project teams to select products that have a verified EPD. The next credit, MRc3, targets the sourcing of raw materials and serves to encourage the use of products that have been extracted or sourced in a sustainably-focused manner. Finally, MRc4, is intended to reward teams that select products that have inventoried ingredients and/or that are known to not be harmful to human health and safety.
LEED v4 has been touted by its supporters to “paint a more complete picture of materials and products, enabling project teams to make more informed decisions that will have greater overall benefit for the environment, human health and our communities, while also encouraging manufacturers to improve their products through innovation” (Todd 2013). However, the changes have been met with some resistance from building professionals. Nadav Malin, a materials and sustainability specialist at Building Green, wrote in September 2012, “building professionals don't necessarily disagree with the direction of the new credits, but are wary of changing the system so radically all at once, and concerned that tools and resources needed to meet the new credits are not yet available”.
There is no doubt that these proposed credits will have a significant impact on project teams pursuing LEED certification; these credits may also impact the role of the structural engineer during the LEED planning process. A sixth comment period was scheduled in March 2013 and the ballot is planned for June 1, 2013.
ReferencesAnderson, J., Silman, R. (2009). “A Life Cycle Inventory of Structural Engineering Design Strategies for Greenhouse Gas Reduction,” Structural Engineering International.
Humbert, S., H. Abeck, N. Bali and A. Horvath. (2007). "Leadership in Energy and Environmental Design (LEED): A Critical Evaluation by LCA and Recommendations for Improvement," International Journal of Life Cycle Assessment, Vol. 12, Special Issue 1, pp. 46-57.
LEED Reference Guide for Green Building Design and Construction v4 Draft. USGBC.
Malin, Nadav. (2012). “A Material Issue”. Green Source Magazine.
Scheuer, C.W., Keoleian, G. A. (2013). Evaluation of LEED Using Life Cycle Assessment Methods, NIST GCR 02-836, 2002.
Todd, Joel Ann. (2012). "Life Cycle and LEED". EDC Magazine.
The Institution of Structural Engineers. (2012). “The Value of Structural Engineering to Sustainable Construction”.