If you have ever been part of a project team seeking LEED certification for a building, you know how critical it is to gain each and every point that was identified by the project team at the start of the project. However, while searching for those points, have you ever considered what is behind the credits and why some are worth one point while others are worth multiple points?
Evolution of LEED
In the early days of LEED, all credits were worth one point. As the rating system evolved, the weighting related to the points associated with credits changed from one credit being worth one point to a credit being worth more than one point. This approach changed because the rating system and categories within were becoming too complex, and the U.S. Green Building Council (USGBC) wanted to create a point allocation process that served as a simplified guide to navigate through LEED’s complex and competing issues. This new approach, also known as credit weighting, has become an important issue as the green building industry has expanded.
In the past, LEED points were arbitrarily allocated by various Technical Advisory Committees–made up by industry professionals-for each of the main categories (Sustainable Sites, Water Efficiency, Energy Efficiency, Materials and Indoor Environmental Quality). Today’s rating system provides a framework to measure a building’s sustainability, and offers flexibility so teams can pick and choose which voluntary credits are most applicable to their projects.
Every version of the rating system has led to an increased sophistication of LEED. When LEED 2009 was introduced, the USGBC felt the earlier versions of LEED did not adequately evaluate the environmental and human benefit-including the building’s indoor air quality, carbon footprint, water use and fossil fuel depletion-of each LEED credit. By weighting certain credits, negative environmental impacts could be mitigated, while positive impacts could be celebrated and promoted.
As part of the enhancement to the rating system, the USGBC implemented impact categories in LEED 2009. These categories stemmed from a computer software tool developed by the Environmental Protection Agency, known as TRACI (Tool for the Reduction and Assessment of Chemicals and other environmental Impacts). The categories include:
- Ozone depletion
- Global warming
- Acidification
- Eutrophication
- Photochemical oxidation (smog)
- Ecotoxicity
- Human health: criteria air pollutants
- Human health: carcinogenic
- Human health: non-carcinogenic
- Fossil fuel depletion
- Land use
- Water use
These categories aimed to evaluating individual materials, not whole buildings. Additionally, they failed to fully represent a holistic look at sustainability. The USGBC’s advisory group noted that the new categories did not address the goals of the organization, and recommended that LEED be further revised.
LEED V4
When the current rating system–LEED v4–was subsequently developed a few years ago, a more transparent analytical framework was added to focus attention to systems performance. The categories were expanded to focus on human health and were ranked based on how the specifically applied to the built environment. The seven categories were defined as:
- Climate change
- Human health
- Water resources
- Biodiversity
- Material resources
- Greener economy
- Community
A related set of new impact categories, focused on the social, environmental and economic goals of LEED were established, and each strategy was measured on its ability to meet those goals, were established. While LEED 2009 focused on environmental problems and how they can be reduced, LEED v4 expanded the categories to emphasize what each LEED certified building should accomplish. The expanded categories are as follows:
- Reverse contribution to global climate change
- Enhance individual human health and wellbeing
- Protect and restore water resources
- Protect, enhance and restore biodiversity and ecosystem services
- Promote sustainable and regenerative material resources cycles
- Build a greener economy
- Enhance social equity, environmental justice and community quality of life
The new credit weightings allow for detailed associations to be made for each credit and enables statistical analysis of the results. This approach results in greater analytical consistency, while also providing a better understanding of the system’s performance through measureable results. This information allows the USGBC to know when goals are being met (both at the Impact Category and strategy level), and how to further refine the system down the line.
The credits and their associated points in LEED v4 have been arranged to motivate project teams to pursue strategies that most effectively address the social, environmental and economic outcomes identified by USGBC. The organization awards more points to the projects that go further in accomplishing the system goals of the seven impact categories.
The issue of credit weighting has become increasingly important as the LEED rating system has evolved. The USGBC’s focus on improving credit weighting throughout every version of LEED is an indication of its commitment to the continuing evolution of the built environment. The LEED rating system, and its various categories and associated points, can be difficult to navigate, but many projects and the communities where they are built are benefiting from the fairly new social impact categories.
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Thomas Taylor, a 30-year veteran of the construction industry and noted expert on sustainability, is a principal and co-founder of St. Louis-based Vertegy. To learn more about Vertegy or Taylor, visit www.vertegyconsultants.com.