Page 124 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

CHAPTER 3

LEED Water Efficiency

he Water Efficiency (WE) category of the U.S. Green Building Council (USGBC)
rating system for new construction version 2.2 (LEED-NC 2.2) and version 2009
T(LEED-NC 2009) consist of three credit subcategories which together may earn a
possible five points in version 2.2 and 10 points in version 2009 maximum, not including
exemplary performance (EP) points. New to version 2009 is the WE prerequisite 1: Water
Use Reduction Required. The notation format for the credits is, for example, WEc1 for
Water Efficiency credit 1. Also, in this chapter, to facilitate easier cross-referencing
between this text and the USGBC rating system, the second digit in a section heading,
equation, table, or figure number represents the credit subcategory number for sections
that deal directly with a USGBC LEED-NC 2.2 or 2009 credit subcategory.
The Water Efficiency portion deals with issues that reduce the use of potable water at the
site and the discharge of wastewater from the site. This will help limit the amounts of
freshwater drawn from our water bodies and aquifers, and then treated for distribution and
use, which strain our freshwater supplies and our water infrastructure. It will also serve to
reduce the wastewater volumes discharged to these receiving bodies. Although several of
the credits in Water Efficiency might include a capital cost investment, all provide a means to
potentially reduce the associated utility costs over the life of the building.
The three subcategories are Water Efficient Landscaping (WE credits 1.1 and 1.2 in
version 2.2 and WE credit 1 in version 2009), Innovative Wastewater Technologies (WE
credit 2 in both versions), and Water Use Reduction (WE credits 3.1 and 3.2 in version
2.2 and WE credit 3 in version 2009). Basically, the first credit subcategory limits the use
of potable water for outdoor uses, the second limits the production or discharge of
wastewaters (black), and the third limits the use of potable water for indoor uses, as
does the new LEED 2009 WEp1. The points for the credits in the Water Efficiency category
are not necessarily individually related to a specific credit. Table 3.0.0 is a summary of
the prerequisites and credits in both versions (2.2 and 2009) with a comparison of the
points available and a summary of many of the major differences.
The prerequisite and credit subcategories available in the Water Efficiency category
are as follows:

• WE Prerequisite 1 (WEp1): Water Use Reduction Required (no previous versions
to LEED 2009)
• WE Credit 1 (WEc1): Water Efficient Landscaping (previously referred to as Water
Efficient Landscaping: Reduce by 50% in LEED-NC 2.2 or 50% Reduction in
LEED-NC 2.1 and also No Potable Water Use or No Irrigation in these earlier
versions and labeled as WEc1.1 and WEc1.2)
• WE Credit 2 (WEc2): Innovative Wastewater Technologies

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