Page 151 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

LEED W ater Ef ficiency 131

In like manner, two, three, or four points for WE credit 3 are obtained if the following
are also true, respectively:

IWUD ≤ . 070 or ≤ 0.65 or ≤ 0.60 for no reuse waters or rainwaters (GW)
IWUB used in residential indoor fi xtures (3.3.17)
Special Circumstances and Exemplary Performance
If there are special circumstances for these credits, a narrative must be submitted
describing these circumstances.
In LEED 2.2, there were two different Innovation and Design (ID) points which
could be obtained related to the WE credit 3 subcategory. One was an EP point, and the
other was based on non-EPAct regulated fixtures.
The EP point available in the ID category for Water Use Reduction as per LEED-NC 2.2
may be awarded by decreasing the water usages as defined in LEED 2.2 WEc3.1 (20 percent)
and LEED 2.2 WEc3.2 (30 percent) by 40 percent. It is related to the overall subcategory and
brings the total LEED 2.2 points available for overall indoor potable water use reduction of
the EPAct regulated fixtures to three if the following inequality is true:
−
IWUD GW
≤ .60 LEED 2.2 (3.3.18)
0
IWUB
In LEED 2.2, project teams were also encouraged to earn an ID credit for reduction of
water usage in non-EPAct regulated and/or process water (non-EPAct) consuming
fixtures. These might include dishwashers and clothes washers for residential or
applicable retail and commercial uses, or cooling towers for applicable uses. There are
still some options available in LEED 2009 for schools. The criterion for LEED 2.2 was
based on a reduction from these changes to non-EPAct regulated or process water
consuming fixtures, which is at least equal to 10 percent of the total design regulated
water use (10 percent of IWUD). Therefore, for the applicable non-EPAct fixtures
involved, the baseline water usage (non-EPActB) and the design water usage (non-
EPActD) should be calculated. An additional LEED 2.2 ID credit might have been
obtained if the following was true:

non-EPActB − non EPActD
-
≥ .010 LEED 2.2 (3.3.19)
IWUD
LEED 2009 grants an EP point for WEc3 if the following is true:
−
IWUD GW
≤ .055 (3.3.20)
IWUB

3.4 Discussion and Overview
Care should be taken to evaluate the site area for the project for the WEc1 credit subcategory
and many of the Sustainable Sites subcategories. Maximizing naturally vegetated open
spaces and designing the project around them can aid in stormwater management,
reducing irrigation needs, lowering urban heat island impacts, and encouraging ecological
diversity and sustainability. In addition, full-time, transient, and design occupancies are
important in the calculations for the WEc2, WEc3, and SSc4 subcategories. These should
be established early in the project phase and used consistently throughout.