commentDesign development began for this 55-story skyscraper in Midtown Manhattan way back in the green-building dark ages of 2003. Nine years later we have our first look at the building's actual energy performance, which confirm prior expectations that One Bryant Park (November 2010) is not, by any stretch, an energy-efficient building. But the full story is not as simple as that. The findings in a nutshell: Actual performance closely matches predicted energy use; site energy use is very high; on-site cogeneration and ice storage are effective at reducing source energy use and energy cost.
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Because the model required for LEED certification assumed perfect construction and operations, the engineers created a second design model to reflect more realistic assumptions. Actual performance beat that second model slightly.
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KEY PARAMETERS
LOCATION New York, New York (Manhattan Island)
Gross area 2.2 million ft2 (204,385 m2)
Cost $1 billion
Completed May 2010
Program Commercial space, trading floors, theater
TEAM & SOURCES
ARCHITECTS Cook + Fox Architects (design); Adamson Associates Architects (executive)
Owners The Durst Organization and Bank of America
Project developer The Durst Organization
Energy use in so-called high-performance buildings is sometimes dramatically different from predictions, but in this case the predictions were pretty good. The design team was able to forecast actual energy use well in part because so much of the energy load runs the bank's data center and trading floor, and those were known during the design process.
Site energy use, measured in terms of Btus consumed in the building, is extremely high for several reasons: The data center and trading floor use lots of energy; the building has long hours of operation; the team invested in cogeneration and ice-storage technologies that reduce energy cost at the expense of higher site energy use; and the designers opted for the aesthetics and daylighting benefits of an inefficient glass curtain-wall system over a more energy-efficient envelope.
By making ice at night and melting that ice to cool the building during the day, the ice-storage system is working well to reduce demand charges and shift cooling load to off-peak hours with lower tariffs, even as it increases overall energy use slightly.
The gas-turbine cogeneration system is a classic "fuel-switching" technology. It consumes natural gas to reduce the amount of electricity purchased. That choice reduces cost because gas is much cheaper than electricity. The system is working more or less as designed to provide nearly all the heat the building needs and about half the electricity, although a failed data cable caused it to go down for two weeks recently. There are hidden costs that muddy the return on investment, however: "We pay over $1 million for a standby connection with Con Edison, but we use almost no steam," complains Don Winston, VP of technical services for the Durst Organization.
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