While designing a building, the professional has myriad questions to consider:
- Is it a good idea to install a roof garden or to add additional insulation to boost the exterior wall's insulation R-factor?
- Does a building in Florida have the same green goals as a similar building in the Pacific Northwest?
- Who or what is the most knowledgeable green information source to help us facilitate our green goals decisions?
To answer these questions and others, the
USGBC devised a priorities list of environmental impact categories in LEED and an associated matrix to help.
Evaluating a building according to its green attributes is one of LEED's lifelong goals. As such, the USGBC combined scientific and market expertise to formulate tools that make assessing green attributes easier, reproducible and transparent. A list of prioritized environmental categories and a Weightings Tool matrix work in tandem to help professionals make well-calculated goals for green building projects.Priorities List
The categories in the priorities list come from the U.S. Environmental Protection Agency's (EPA) TRACI computer software program. The EPA uses TRACI to analyze impacts assessments for their environmental programs, such as lifecycle assessments, industrial ecology, process design and pollution prevention.
The USGBC thought it made sense to use TRACI categories because they have proven helpful to the EPA. In addition to the TRACI categories, the USGBC also used impact weightings research and information from the National Institute of Standards and Technology (NIST) to put the categories in a ranked listing, with the first having the most positive impact potential:
1. Climate Change
2. Indoor Environmental Quality
3. Resource Depletion
4. Human Health Criteria
5. Water Intake
6. Human Health - Cancerous
7. Eco-toxicity
8. Entrophication
9. Habitat Alteration
10. Human Health - Noncancerous
11. Smog Formation
12. Ozone Depletion
13. Acidification
This new priorities list is truly revolutionary because it dispels the idea that "any green building attribute is equal to another." Any efforts invested in sustainability are rewarded, but some measures are more effective than others in helping building owners reach not just their desired level of LEED certification, but also a level of environmental efficiency that guarantees the best green dollar value per square foot.
Weightings Tool Matrix
Perhaps the biggest change in the latest LEED Rating System release is the Weightings Tool Matrix, a pre-programmed and technically complex Excel spreadsheet that recalculates the amount of points awarded for meeting each credit. "Credit re-weighting ... is the redistribution of the available points in LEED so that a given credit's point value more accurately reflects its potential to either mitigate the negative environmental impacts of a building or promote positive impacts." (1)
The Weightings Tool can also be used on a case-by-case basis to decide which credits are most beneficial for any particular green project. The downloadable Excel spreadsheets can be downloaded from the USGBC website. These spreadsheets are still somewhat rudimentary, but the USGBC plans to further refine and develop them for more powerful use.
Credit Weightings Examples
Because the priorities list puts the greatest emphasis on energy efficiency and the reduction of CO2 emissions, it makes sense that the number of possible credits in LEED's energy and atmosphere (EA) category was increased from 30 points in V2.2 to 35 points in 2009 V3. The energy efficiency credit itself, within the EA category, also increased from 15 to 18 points. By investing in renewable energy, a project is now eligible for two more points, which raises the total to six.
Additional examples, as cited on usgbc.org, are listed below (2):
- For credit 4.1 of Sustainable Sites: The proximity of a building to public transportation allows for building occupants to utilize alternative transportation methods which in turn has impacts associated with fossil fuel depletion, land use, acidification, ozone depletion, smog formation, ecotoxicity and overall human health effects caused by reducing single-occupant vehicle use. It also affects a large component of the building's environmental impact - its carbon footprint associated with transportation to and from the building. LEED for New Construction 2009 has increased the point value of this credit.
- For the Water Efficiency Credit Category: Reduction in water use associated with irrigation outside the building and fixture/fittings use inside the building has impacts on resource depletion and water shortages leading to agricultural, human, plant, and animal effects. While the impacts of these credits were primarily in water use, the benefits of water reduction are heavily emphasized in LEED for New Construction 2009.
- For credit 2 of Energy and Atmosphere: Utilizing renewable energy for a building's energy needs reduces the dependency on less environmentally sound energy sources, which have a variety of impacts on the environment and human health. Using renewable energy impacts a building's carbon footprint, contribution to fossil fuel depletion, ozone depletion and rate of particulates (which can lead to chronic and acute respiratory symptoms).
An Age of Thinking and Adjustment
Even with the leaps and bounds LEED has made in its research and rating system revisions, V3 2009 still represents a period of "thinking" that holds a powerful presence on the green building front. It will take time and deliberation to develop a working understanding of how to design a building that delivers the best possible positive impact on its surrounding environment and proximate human health.
To find out more about the LEED V3 2009 credit weightings,click here, or visit http://www.usgbc.org/DisplayPage.aspx?CMSPageID=1971#weightings
