Section 2: Individual LEED Credit Reviews
Office Building Modernization
Office Building models associated with
increased zone air temperatures.
The GSA energy use target for this building is
50,00055,000 BTU/GSF/year, based on a
As with the Courthouse, the baseline heating and
Washington, D.C. location.
cooling plants in the Office Building models are
assumed to meet the minimum ASHRAE
As previously noted, two variants of the Office
performance requirements. For the cooling plant,
Building modernization are tracked in the study--
the GSA reference includes two 330-ton water-
one which includes a minimal faade renovation
cooled centrifugal chillers and one 135-ton water-
(window replacements and cleaning/recaulking of
cooled screw chiller, as compared to two 397.5-ton
the exterior facade); and one that includes a full
centrifugal chillers in the ASHRAE case. This
faade renovation (new windows, new precast
results in different load management strategies
concrete panels for floors 39, reduced glazing
between the two cases, which are reflected in the
areas on floors 39). The baseline models of both
energy model.
of these scenarios--defined in the Reference Cost
Overall, the minimal faade renovation baseline
Estimates of Appendices L and M--include a
has a calculated annual energy use of 49,200
number of specific building and MEP system
BTU/GSF/year. Using the ASHRAE Energy Cost
features to meet the energy use target. Most of the
Budget Method, the building's annual energy cost
key building features in the Office Building models
was calculated to be 14.4 percent less than a "code
are identical to those described in the Courthouse
compliant" energy model that meets the minimal
baseline. The common features include:
requirements of ASHRAE 90.11999. This results
High-Performance Glazings (Ucenter of glass =
in 2 LEED energy points using the "Existing
0.32, Solar Heat Gain Coefficient = 0.30,
Buildings" point scale. For the purposes of the
Visible Transmittance = 57 percent)
study, all of the "minimal faade" Office Building
Efficient Lighting (1.1. watts/SF for office
scenarios have added additional EEMs in order to
areas)
achieve 3, 5, or 7 energy points respectively, as
shown in Table EA1-2.
Variable speed drive fans at air handlers
Variable speed drive pumps (30 percent
The full faade renovation baseline has a calculated
minimum part load ratio)
annual energy use of 47,600 BTU/GSF/year. The
Waterside economizer at cooling towers
lower energy use is primarily attributable to the
Wetbulb reset at cooling towers
reduced area of glazing in the full facade scenario
Carbon monoxide control of garage
(40 percent of the overall wall area vs. 60 percent
ventilation fans
in the minimal faade case). Using the Energy Cost
Budget Method, the building's annual energy cost
Differences include the following:
was calculated to be 18 percent less than the 90.1
model. This results in 3 LEED energy points using
The opaque walls in the minimal faade
the "Existing Buildings" point scale. For the
renovation scenarios have an overall R-value
purposes of the study, all of the "full faade"
of 10 (R-values include air films). The opaque
Office Building scenarios have added additional
walls in the full faade renovation scenarios
EEMs in order to achieve 5 or 8 energy points
have an overall R-value of 10 on the lower
respectively, as shown in Table EA1-2.
two floors and 15.2 on floors 39 (R-values
include air films).
The roofs have an overall R-value of 16.1 (R-
values include air films). This meets the
minimum ASHRAE requirement.
The office buildings use overhead air
distribution systems (as opposed to the
underfloor air distribution system in the
Courthouse). There are no savings in the
GSA LEED COST STUDY
76
Previous Page
