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Energy Efficiency Upgrades Save $150,000 in Luxury Condo Tower

Condo unit-owners in the luxury glass skyscraper at 252 E. 57th St. in Sutton Place enjoy some enviable perks, but until recently, the building’s energy efficiency was not one of them. However, over the past year, the building has saved $150,000 on its energy bills, thanks largely to a partnership with Parity, a company that helps fine-tune building systems for optimum efficiency. The work has also eliminated Local Law 97 penalties for the condo in 2030.

When the sponsor finished construction of the tower in 2016, the mechanical systems, including heating and cooling, were “running wild,” says Dan Donnelly, a resident of the 65-story tower and an energy consultant. “In terms of energy we were performing in the bottom 5% of New York City buildings.” Saddled with a D energy grade and annual emission penalties estimated at $65,000 in 2030, the board set up an energy committee, led by Donnelly, to figure out how to reduce the building’s carbon footprint.

Part condo, part rental. The buildng contains condo and rental units, which have different mechanical systems. The rentals use heat pumps, but the condo apartments use four gas-fired boilers for heating and compressors to operate chillers for cooling. Each of the 95 condo units is equipped with four-pipe fan coil units for heating and cooling at any time. This is important in the winter, when the sun shines through the curved glass facade and heats some of the apartments to 85 degrees Fahrenheit. “The building experiences intense solar gain, resulting in huge cooling loads even in the dead of winter,” says Kevin Lin, the director of systems integration at Parity. 

Switching to free cooling. Lin, the lead engineer tasked with reducing the building’s emissions, says the savings were largely driven by maximizing evaporative cooling instead of mechanical cooling. Evaporative cooling, also known as free cooling, uses outdoor temperatures via the cooling tower to reject heat from the water in the system. This requires less energy than using the compressors to operate a chiller. “When the system was designed, it was relying a lot more on the chiller,” Lin explains. The resident manager was then tasked with manually switching to free cooling when outdoor conditions allowed, something that could easily be overlooked. With the new system, the transition to free cooling takes place automatically. “Last December we were able to reduce peak demand by 300 to 400 kilowatts, which is significant,” Lin says. 

Modifying makeup air units. Another area of savings came from modifying the building’s makeup air units, which replace air that is ventilated from apartments with exhaust fans. The condo apartments also have high-end kitchen range hoods that remove a large volume of air. The makeup air units were working at the maximum, even though the range hoods were not in use all day. “We were able to adjust the airflow so the load met the demand,” Lin says. 

Variable frequency drives. Similarly, the domestic hot water preheating system wasn’t set up to be energy efficient. Water was being preheated 24/7, even during the day, when demand was low. “A lot of times the pump was just moving water when there was no water on the other side that needed to be preheated,” Lin says. This was achieved by a combination of variable frequency drives that heated water automatically based on demand.

Sum of all the parts. The building’s energy-efficiency upgrades received NYSERDA incentives of around $190,000, reducing the project cost to around $135,000. Parity, which guarantees annual savings, projected that the building would save at least $90,000; thanks to the new system, it saved an additional $60,000 in the past year. Donnelly says a big part of its success was Parity’s on-site training for building staff and residents. “Now we are running the building in a very different way,” he says. Parity also monitors maintenance of the system to make sure there are no problems that might affect energy efficiency if failures go undetected.

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