Section 2: Individual LEED Credit Reviews
LEED Credit WE-1.2:
Basis for Cost Assumption
Water-Efficient
For the purposes of this study, Credit WE-1.2 was
pursued only in the Courthouse model--the scope
Landscaping -
of the Office building modernization does not
No Potable Use or
include site work.
No Irrigation
As noted in credit WE-1.1, a "GSA Base Case" of
site planting assumptions was developed for the
Courthouse model, based on a review of several
current GSA Courthouse projects. The general
Intent
planting assumptions for the model (based on
Limit or eliminate the use of potable water for
approximately 34,600 square feet of planting area)
landscape irrigation.
were as follows:
Turf grass: 15 percent of the planting area
Requirement
Mixed vegetation (shrubs, groundcovers,
Use only captured rain or recycled site water to
perennials, understory trees): 40 percent of the
eliminate all potable water use for site irrigation
planting area
(except for initial watering to establish plants),
Groundcovers only: 40 percent of the planting
OR do not install permanent landscape irrigation
area
systems.
Street trees: 5 percent of the planting area.
(1 point)
Since GSA's P100 already encourages the selection
of plant species to minimize supplemental
watering, the assumption made for this credit is
Cost Impact = 2
that, in some projects, plantings can be specified
that eliminate the need for an irrigation system.
1
2
3
4
5
Representative plant selections were made based
on a Washington, DC site location. The following
GSA
No
Low
Moderate
High
planting list is similar to the one from credit WE-
Standard
premium,
premium
premium
premium
(no cost)
psble svgs
(<50K)
(50-150K)
(>150K)
1.1; however, some of the undercover trees and
shrubs have been changed to reflect lower water
Practical Applications
use species:
Street trees: Honeylocust and Japanese Zelkova
The simplest and least expensive means of
Understory trees in planting beds: Mix of Crepe
achieving this credit is to select native and/or
Myrtle, Virginia Pine, and Eastern Red Cedar
adapted landscape plantings that eliminate the need
for a permanent irrigation system. Well-integrated
Shrubs in "barrier gardens": Mix of Wax Myrtle,
landscape designs may include additional Low
Maple-leaved Viburnum, and American Holly
Impact Development strategies, such as rain
Shrubs and perennials in planter areas: Mix of Wax
gardens or vegetated swales, to both eliminate
Myrtle with various perennials (New England
irrigation and retain stormwater runoff on-site.
Aster, Wild Bergamont, Blue False Indigo,
Early Coneflower, Black-eyed Susan and
Systems that collect, store, and recycle greywater or
others)
stormwater can also be used to achieve this credit;
Groundcovers: Mix of Leadwort, Striped
however, these technologies are considered
Wintergreen, Fragrant Sumac, and Mountain
unlikely for most GSA projects.
Stonecrop
Turf grass: Fescue blend sod
GSA LEED COST STUDY
58
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