Section 3: Synergistic Credits
Basis for Cost Assumption
Courthouse: Credit SN-2
The cost premiums for Credit SN-2 are based on
the installation of 30,550 SF of vegetated roof area
Combines:
(3,700 SF on the roof above the 2nd floor), plus the
Credit SS-6.1
PV panel area (6,000 SF) and electrical distribution
costs defined in the individual credit estimate EA-
Stormwater Management, Rate and
2.1.
Quantity
Summary of First Cost Impacts
Credit SS-7.2
Heat Island Effect, Roof
Credit EA-2.1
Individual Credit Costs
Renewable Energy, 5%
Credit SS-6.1b ........................................... 8,170
Credit SS-7.2b ........................................... 5,353
Credit EA-2.1 ............................................ 7,586
Description
Synergistic Credit SN-2
Credit SN-2 identifies the synergies available
through a vegetated roof installation. The
Total Credit Cost ...................................
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,378,943
synergistic credit scenario is based on a 4-inch-
Cost Impact ($/GSF)............................26/GSF
deep (extensive) vegetated roof covering 65
Cost Impact (%) ............................................2.40%
percent of the overall roof area of the Courthouse
(approximately 30,550 square feet). The vegetated
roof results in a reduction in site imperviousness of
Applicable Scenarios
25.8 percent, meeting the stormwater criteria of
SS-6.1 (25 percent decrease in the rate and quantity
Credit SN-2 is used in the Courthouse scenario 6A
of stormwater runoff). At the same time, it also
(Gold).
meets the heat island reduction criteria of credit
SS-7.2 (vegetated roof for at least 50 percent of the
roof area).
For the purposes of the study, credit EA-2.1
(Renewable Energy, 5%) is also included in this
synergistic credit combination. This is because the
30,550 SF of vegetated roof area, together with the
6,000 SF of photovoltaic panels needed to achieve
credit EA-2.1 (supply at least 5 percent of the
building's total energy use through on-site
renewable systems), requires an overall roof area
that is greater than the upper roof of the
Courthouse (assuming cooling towers, access areas,
etc.). To compensate, the lower roof over the
second floor also becomes a vegetated roof system.
Three LEED credits are achieved with credit
SN-2.
GSA LEED COST STUDY
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