DETAIL Project of the Month — May 2009
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RSS FeedBank of America Tower
Architects: Cook + Fox Architects, New York
Structural engineers: Severud Associates, New York
Mechanical engineers: Jaros, Baum & Bolles, New York
Exterior wall consultant: Israel Berger Associates, New York
Energy consultant: Viridian Energy & Environmental,LLC, New York
LEED consultant: E4, Inc, New York
BOA tenant architect: Gensler, New York
Construction: Tishman Construction Corporation
After the Empire State Building, the nearly completed Bank of America Tower is the second-highest skyscraper in New York. Located close to Times Square, the building is the outcome of many years of collaboration between two powerful instances with common interests. As early as the 1990s, the Bank of America had expressed the wish to create a new iconographic headquarters building in New York. Not only should it manifest its presence visually in Midtown Manhattan; the bank wished to secure the loyalty of members of the staff through the creation of first-class working conditions. In the context of growing environmental and energy awareness in the United States, the financial institution also sought to demonstrate the compatibility of economic and ecological interests with showpiece architecture based on sustainable principles.
Over a period of 40 years, the property developer Durst had bought up small areas of land between Broadway and 42nd Street to form the largest continuous building site in Manhattan (0.8 ha). Here, too, the marketing potential of sustainable construction had been recognized, and experience was gained in the erection of various “Green” buildings. Now, all the available processes and forms of technology were to be applied in a beacon project designed to a really large scale. Richard Cook and Robert Fox, two architects who specialize in sustainable forms of construction and who had collaborated with the Durst family on many occasions previously, were awarded the planning commission in 2003. By the autumn of 2008, the Bank of America Tower, with its fine-sounding address — One Bryant Park — was already half occupied. Construction work to the tip and the plinth should be completed this summer.
With its crystalline form, the structure stands out boldly against the surrounding developments. As a “signature building”, it has a high recognition value as well as the requisite iconographic presence. Over the upper two thirds of its height, the corners are splayed slightly inwards, making the volume appear lighter and more dynamic. This feature also improves the natural lighting and the quality of the air in the street space below, as well as extending the visual axes from the interior, which would normally be restricted by the typical block grid of New York. Tilting the facade slightly towards the sky also means that more daylight enters the offices. The rectangular, seven-storey plinth structure with extensive spaces for traders occupies the entire area of the block. New subway exits and a public “urban garden room” — an extension of Bryant Park diagonally opposite — create many links to the surrounding urban space.
The decision to locate the building in these exceptionally dense surroundings, thereby exploiting local public transport as a means of access, gained points in advance for the desired environmental certification. One Bryant Park is the first office tower in the US to be nominated for LEED Platinum, the highest ecological rating awarded by the American Green Building Council.
Most building projects in Europe that are environmental showpieces make no secret of the architectural and technological measures they incorporate to generate or save energy. In contrast, one of the distinguishing features of the tower at One.
Bryant Park is that its ecological achievements, which are outstanding for American circumstances, are not glaringly evident in the architecture. There are no photovoltaic cells, for example, no multilayer facades or wind rotors, even though there was certainly no lack of familiarity with these forms of technology.
Ten years earlier, the property developer Durst had erected the nearby Condé Nast Tower, a Green structure with photovoltaic panels integrated in the facade. These did not prove so convincing from an economic point of view, however. As a result of this experience, the clients decided to implement only measures that were likely to show an amortization of the additional investment sum (2 per cent of the project costs) within the first five years of use. As long as they observed these parameters, the planners were free to implement their sustainable concepts.
The other important constraint was to keep an eye on the evaluative criteria for the desired LEED certificate, and these focus only marginally on visible material or architectural results. Nearly a quarter of the points to be gained are awarded for criteria that have to do with the site itself. Others are related primarily to the construction process; for example, obtaining materials as far as possible from the surrounding area within a radius of roughly 800 km. This is meant to reduce energy consumption for transport. Further potential for savings lay in the use of 60 per cent recycled steel, something that is quite normal in the US. One innovation was the substitution of recycled material (granulated blast-furnace slag) for cement in nearly half the concrete used in the building (see box left). The list of measures of this kind relating to the actual construction process extends to the reuse of cable drums and certified timber as cladding material.
Recycled Concrete Materials at One Bryant Park
Worldwide, cement manufacturing accounts for approximately five per cent of total carbon dioxide emissions, making this one of the largest sources of greenhouse gas in the building industry. Cement makes up about 15 per cent of any concrete mix. Green buildings can, therefore, reduce the negative impact on the environment by using substitute materials for a portion of the cement in the foundations and superstructure.
Granulated blast-furnace slag (GBFS) is a waste product from the process of smelting steel. Formed from the chemical interaction of lime with minerals found in iron ore, the resulting material is very similar to Portland cement. Together with fly ash, which is a waste product of coal-fired power generation, GBFS can help to achieve significant reductions in CO2 emissions, at a rate of almost one tonne of CO2 for every tonne of cement saved.
It has been shown that substituting GBFS for cement has no negative effect on the performance of the concrete. On the contrary, a denser, more durable material is produced using slag cement. The Helena in New York City, a residential development owned by the Durst organization, was an early project in which a high percentage of slag cement was used. In preparation for this project, the owners commissioned studies that showed that the substitution of GBFS for up to 45 per cent of the cement increases the strength of the concrete by 25 per cent. Contractors were initially sceptical about using such a high percentage of GBFS. This was because the additional strength comes later — after 56 days, instead of 28 days in the case of ordinary concrete — and the initial setting may also be slower. The owners and the design team resisted the contractors’ wish to have more traditional mixes approved as a back-up option. In the end, the finishing and the removal of formwork were no problem, and the use of alternative mixes was not necessary.
In the Bank of America project, GBFS was again substituted for 45 per cent of the cement in all foundations and superstructure concrete. This time, very little resistance was put up by the concrete suppliers and the contractors. Minor problems encountered in pumping some of the higher strength mixes were resolved. With a total concrete volume of nearly 66,000 m3, more than 17,000 tonnes of cement were saved by substituting GBFS. An industrial waste product was thus turned into a valuable material, saving the emission of almost 16,000 tonnes of carbon-dioxide into the atmosphere. In addition to the environmental benefits, the concrete creates stronger shear walls and denser foundations — an important consideration for a building in which the latter are below the groundwater table.
LEED certification
The details listed below are the individual results of preliminary certification as aimed at or expected. They are therefore only provisional. The final certification for LEED Platinum will take place after completion of the building, which is scheduled for the spring of 2010.
The certification process for One Bryant Park is based largely on LEED-CS, version 2.0. The architects are making their submission in accordance with LEED standards for core and shell.
Credit Criteria LEED (Core and Shell v2.0)
Total credits: 51 / 61
(Certified: 24-28, Silver: 29-34, Gold: 35-44, Platinum: 45-61)
(number of credits achieved/maximum number of credits available)
Sustainable Site (11/15)
Erosion & Sedimentation Control (prerequisite), Site Selection (1/1), Development Density (1/1), Brownfield Redevelopment (1/1), Alternative Transportation (2/4), Site Development( 1/2), Stormwater Management (2/2), Reduce Heat Islands (2/2), Light Pollution Reduction (0/1), Tenant Design & Construction Guidelines (1/1)
Water Efficiency (5/5)
Water Efficient Landscaping (2/2), Innovative Wastewater Technologies (1/1), Water Use Reduction (2/2)
Energy + Atmosphere (13/14)
Fundamental Commissioning (prerequisite), Minimum Energy Performance (prerequisite), CFC Reduction in HVAC&R Equipment (prerequisite), Optimize Energy Performance (8/8 points pursued), Renewable Energy, 1% (0/1), Enhanced Commissioning (1/1), Ozone Depletion (1/1), Measurement & Verification (2/2), Green Power (1/1)
Materials + Resources (6/11)
Storage & Collection of Recyclables (prerequisite), Building Reuse (0/3), Construction Waste Management (2/2), Resource Reuse, Specify 1% (0/1), Recycled Content (2/2), Local/Regional Materials (1/1), Certified Wood (1/2)
Indoor Env. Quality (11/11)
Minimum IAQ Performance (prerequisite), Environmental Tobacco Smoke (ETS) Control (prerequisite), Carbon Dioxide (CO2) Monitoring (1/1), Increase Ventilation Effectiveness (1/1), Construction IAQ Management Plan, During Construction (1/1), Low-Emitting Materials, Composite Point Score (3/3), Controllability of Systems, Thermal Comfort (1/1), Indoor Chemical & Pollutant, Source Control (1/1), Thermal Comfort, Comply with ASHRAE 55-2004 (1/1), Daylight & Views (2/2)
Innovation + Design (5/5)
Innovation in Design (4/4), LEED Accredited Professional (1/1)
For more information on DETAIL magazine, please visit DETAIL's Project of the Month page.
This article is an excerpt from DETAIL — Review of Architecture
DETAIL is the international magazine dedicated to the pursuit of excellence in architectural design and engineering. Every issue covers a specific construction topic, illustrated contemporary examples and carefully chosen documented material from architects and trade experts — providing architects and engineers with an invaluable source for design and construction ideas.
From 2009 DETAIL is complemented by two additional issues DETAIL Green — the specialist journal on all aspects of sustainable planning and construction.
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