Section 2: Individual LEED Credit Reviews
LEED Credit WE-1.1:
these technologies are considered unlikely for most
GSA projects.
Water-Efficient
Basis for Cost Assumption
Landscaping -
Reduce by 50%
For the purposes of this study, Credit WE-1.1 was
pursued only in the Courthouse model--the scope
of the Office building modernization does not
include site work.
Intent
For the Courthouse, calculations were performed
Limit or eliminate the use of potable water for
(using the procedures developed in the LEED
landscape irrigation.
Version 2.1 Reference Guide) to determine
measures that would achieve a 50 percent
Requirement
reduction in irrigation water use. Details of the
Use high efficiency irrigation technology, OR
calculation procedures are included in the
use captured rain or recycled site water to reduce
"Supporting Calculations" section below.
potable water consumption for irrigation by 50%
The calculations revealed that the credit could be
over conventional means.
achieved using the following combination of
(1 point)
strategies:
Limit turf grass to 15 percent of the site's total
planting area. This was already the default
Cost Impact = 2
assumption for the Courthouse site; therefore
there was no cost impact.
Employ timer and rain sensor controls for the
1
2
3
4
5
pop-up sprinkler irrigation system (the sprinkler
GSA
No
Low
Moderate
High
system extends to all planting areas on the site
Standard
premium,
premium
premium
premium
other than street trees). GSA's P100 requires
(no cost)
psble svgs
(<50K)
(50-150K)
(>150K)
these types of irrigation controls, so no cost
premium is included.
Practical Applications
Specify groundcovers with low water
consumption needs (classified as having a low
Irrigation systems are commonly installed in GSA
"species factor" in the LEED calculations).
projects. Strategies for reducing irrigation water by
Low-water use groundcover species are
50 percent include the following:
available in most areas at no cost premium;
therefore this measure was not assumed to
Select native and adapted plant species that
impact costs. GSA's P100 also encourages plant
require minimal (or no) supplemental watering
species selection to minimize the need for
after establishment. Limit turf grass areas.
supplemental watering.
Employ automatic irrigation system controls,
particularly for sprinkler systems. Controls
The credit was therefore considered to be
include timers, rain sensors, and soil moisture
achievable with no cost impact.
sensors.
Employ drip irrigation systems in lieu of
For the purposes of the study, planting selections
sprinkler systems for non-turf planting areas.
were based on a Washington, DC site location. The
representative plantings assumed for this credit are
A combination of the above strategies will typically
listed as follows:
be required to meet the 50 percent water reduction
threshold.
Street trees: Honeylocust and Japanese Zelkova
Understory trees in planting beds: Mix of Eastern
The use of greywater and/or captured stormwater
Redbud, Flowering Dogwood, Bald Cypress
can also be used to achieve this credit. However,
GSA LEED COST STUDY
53
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