Luxury Manhattan Condo Saves $150,000 With System Tweaks

Condo unit-owners in the luxury glass skyscraper at 252 East 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 in 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 building beyond 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 facing 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.

The building is part condo and part 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 are equipped with four-pipe fan coil units for heating and cooling at any time. This is important when the sun in winter shines through the curved glass facade, heating some of the apartments to 85 °F. “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. 

Lin, the lead engineer tasked with reducing the building’s emissions, says the savings were largely driven by maximizing evaporative over mechanical cooling. Evaporative cooling, known as free cooling, uses outdoor temperatures via the cooling tower to reject heat from the water in the system, which uses 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 kW, which is significant,” Lin says. 

Another area of savings came from modifying the building’s make-up 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 make-up 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. 

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 (VFDs) that heated water automatically based on demand.

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.