Section 2: Individual LEED Credit Reviews
New Courthouse
chillers) in the baseline model meet the minimum
The GSA energy use target for this building is
ASHRAE performance requirements. For the
45,00050,000 BTU/GSF/year, based on a
cooling plant, GSA's P100 requires at least three
Washington, DC location. The baseline
chillers when the building load is over 500 tons.
Courthouse model--defined in the Reference Cost
Because of this, the Courthouse model includes
Estimates of Appendix K--includes a number of
two 325-ton water-cooled centrifugal chillers and
specific building and mechanical, electrical, and
one 130-ton water-cooled screw chiller, as
plumbing (MEP) system features to meet the
compared to two 390-ton centrifugal chillers in the
target. These include:
ASHRAE case (a more typical approach). This
results in different load management strategies
High-Performance Glazings (Ucenter of glass =
between the two cases, which are reflected in the
0.32, Solar Heat Gain Coefficient = 0.30,
energy model.
Visible Transmittance = 57 percent)
Opaque Walls with overall R values of 8.4 on
Overall, the baseline building has a calculated
the lower two floors and 15.2 on floors 3-5
annual energy use of 47,800 BTU/GSF/year.
(R-values include air films)
Using the ASHRAE Energy Cost Budget Method,
the baseline building's annual energy cost was
Roofs with overall R values of 23.8 (R-values
calculated to be 16.9 percent less than a "code-
include air films)
compliant" energy model that meets the minimal
Lighting power densities of 1.1. watts/SF for
requirements of ASHRAE 90.11999. This results
offices, jury rooms, and judges chambers
in 1 LEED energy point, which is achieved at no
Underfloor air distribution Because this
additional cost to the project (since it is a GSA
system uses a displacement ventilation
requirement and is included in the baseline costs).
approach, the zone air temperatures for
cooling are assumed to be, on average, 1.5
Two additional energy-efficiency scenarios were
degrees higher than in the ASHRAE 90.1
created to earn 3 and 5 LEED energy points,
case, which assumes overhead supply and
respectively. The additional EEMs required to
return.
achieve the points are identified in Table EA1-1. A
Variable speed drive fans at air handlers
description of the cost impact assumptions for the
Variable speed drive pumps (30 percent
individual EEMs follows.
minimum part load ratio)
Waterside economizer at cooling towers
Wetbulb reset at cooling towers
Carbon monoxide control of garage
ventilation fans
GSA LEED COST STUDY
74
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