A tower to admire

From breaking new ground on Third Avenue in the 1950s to installing fuel cells in buildings in the 1990s, The Durst Organization has consistently been one of New York City’s boldest real estate developers.

The Bank of America Tower at One Bryant Park, in the heart of Midtown Manhattan, is the latest example of how Durst’s innovation continues to reshape the city’s skyline. Magnificent design goes hand in hand with cutting-edge technology to produce advanced environmental benefits.

The tower is built from recycled steel and a concrete mix containing about 45 percent slag and fly ash, which are by-products of steel production. Durst’s ambition during construction was to obtain as much of the material as possible from within a range of 800 kilometres (500 miles). This allowed for the builders to cut greenhouse gas emissions by limiting transport distances as well as by reducing heavy concrete production and other material refining processes.“This is ‘Ice Stone’,” says Jordan Barowitz, director of external affairs at Durst, touching a surface on the front desk. “It’s made out of recycled glass, and we used this material in the lavatories as well, in place of what would have otherwise been stone.” The material is manufactured in Brooklyn, just across the East River from Manhattan.

Barowitz and his colleague Don Winston, vice president of technical services, point out other “green” features in an office space on the 49th floor. “The floor and the ceiling are bamboo, which is rapidly renewable, unlike hardwood floors from old-growth forests,” Winston says. “The carpets are made from recycled materials.” 

But it is 50 floors down that the real savings are made. Three stories below ground, the building features some of the most sophisticated heating, ventilation and air-conditioning equipment in the world. There, Alfa Laval plate heat exchangers are used in parallel with the building chillers to save energy. During the four to five months of the year when ambient temperatures are low enough, outside air and a cooling tower are used to produce chilled water in the plate heat exchangers. This reduces or eliminates the need for mechanical refrigeration and dramatically cuts the use of electricity to cool the building. Appropriately, the system is called “free cooling”.

But even in the height of summer, One Bryant Park can save energy through the use of ice thermal storage in the basement. “We have a chiller that is dedicated to ice making,” Winston says. “It’s part of a closed loop system where an ethylene glycol solution circulates through the chiller and a coil of plastic tubing in the ice storage tanks. The cold glycol solution produced in the chiller simply freezes the water surrounding the coils in the tanks.”

All this happens at night, when the cost of electricity to run the chiller is at its lowest. At 8 am, when the cost of electricity climbs, the cycle is reversed and the ice melts.

“That’s when the glycol solution is circulated between the ice tanks and the Alfa Laval plate heat exchangers, which then essentially act as a chiller,” Winston says. The glycol is between –8 and –3 degrees Celsius (17.6 and 26.6 Fahrenheit), depending on the point in the ice-melting cycle.

But cooling with ice to limit the use of peak-hour electricity isn’t the only energy-saving measure The Durst Organization has taken. The building is also equipped with a cogeneration plant that employs more Alfa Laval heat exchangers and generates 4.6 megawatts of electricity, or 75 percent of the annual electrical energy consumed by the building. “The exhaust gas from the engine goes through a heat-recovery boiler and produces steam,” Winston says. “The steam is then used to heat the building in the winter and to run a smaller absorption chiller during the summer. We use somewhere around 70 percent of the total energy in the natural gas we use as fuel, instead of about 30 percent that is used at a utility power plant.”

That saves money and also cuts carbon dioxide emissions, but Durst is still rolling out its full operating protocol. Some construction remains, even though the tower already houses Bank of America’s New York headquarters.

Among the eco-friendly features that will be up and running soon is a system to collect rainfall and reuse other water. The water will ultimately be used as make-up water in the building’s cooling towers and for toilet flushing. The total water conservation programme, including waterless urinals, will save some 38 million litres (10 million gallons) a year.

“We had to think about everything,” Winston says. “It’s hard to build something with so much glass and still be energy-efficient. It harvests a lot of daylight, but it also comes with challenges in thermal comfort. Regarding the green part of this, that’s just how The Durst Organization is doing it. The green commitment is our way.”

“From a leasing perspective it’s also a compelling selling point,” Barowitz adds. He says tenants such as banks and law firms are happy about lower energy costs, but they also see a value in investing in their people. Ample light and clean air make the employees happier and more productive.

“Building like this is more challenging, but you have to take risks in development,” Barowitz says. “Not everyone has the stomach for it, but Durst has always been in the vanguard, all the way from the 1950s.”

Since the building is brand new and not all the systems are up and running yet, there are not enough data to say for sure how One Bryant Park will measure up to other skyscrapers in terms of environmental savings. But the structure is heavily instrumented, and the goal is to make numbers public in 2011.

“We’re absolutely satisfied so far,” Winston says. “There are many areas, especially from a technical perspective, where we have exceeded any building I’ve ever been involved with.”