Page 129 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers
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LEED W ater Ef ficiency 109
Water Efficiency Prerequisite
WE Prerequisite 1: Water Use Reduction Required
This prerequisite is new to LEED 2009 and is essentially what was worth one point
under water use reduction in LEED 2.2. It requires that the design water use for the
building, not including irrigation, is 20 percent less than a baseline. The calculations are
different for commercial uses and residential uses and include only the following
fixtures or fixture fittings, if included in the project: water closets, urinals, lavatory
faucets, showers, kitchen sink faucets, and prerinse spray valves.
The values to use for the baseline and the applicable calculations are in the section
of this book entitled 3.3 WE Credit Subcategory 3: Water Use Reduction.
3.1 WE Credit Subcategory 1: Water Efficient Landscaping
The intention of this credit subcategory is to reduce the use of potable water or natural
surface waters or natural groundwater for outdoor irrigation. In LEED 2.2, WEc1.1 was
worth one point, and WEc1.2 was worth one point in addition to the point for WEc1.1. In
LEED 2009, these two are combined into a single WEc1 subcategory worth either two
points or four points depending on the extent of compliance.
Potable water is water that is assumed to be acceptable for human consumption.
Strategies include using more drought-tolerant plants in landscape beds near pavements
and buildings, keeping native vegetation when possible, and using recycled waters for
irrigation. Figure 3.1.1 shows a landscape bed where several drought-tolerant species
FIGURE 3.1.1 Landscape bed in a subdivision in Columbia, S.C., where several drought-tolerant
species reduce irrigation needs. (Photograph taken July 14, 2007.)