252 East 57th Street

252 East 57th Street is a luxury NYC high-rise building in Manhattan. The building is part condo and part rental – they have different HVAC 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.

Their HVAC systems were “running wild,” according to former board president Dan Donnelly. “In terms of energy, we were performing in the bottom 5% of New York City buildings.” The building has a D energy grade and faced LL97 penalties estimated at $65,000 in 2030.

The board set up an energy committee, led by Dan Donnelly, to figure out how to reduce the building’s carbon footprint.

Gene, the former Resident Manager, referred Parity to Dan for a high-level and technical Parity overview. Dan was already well-informed about LL97 and building/HVAC efficiency. He was very keen on automation and understood he took the building as far as he could with the existing building staff and Building Management System (BMS) in place.

The large limitation and problem at 252 was with the operation of their HVAC systems. Parity was able to fill in that gap with our control optimization software. The project also included a large upgrade to their BMS.

We projected that we would save 252 East 57th Street at least $90,000 in utility costs during the first year. We over delivered and saved the building $165,917.

Our 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 the compressors to operate a chiller. “When the system was designed, it was relying a lot more on the chiller,” Kevin 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,” Kevin 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,” Kevin 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,” Kevin says. This was achieved by a combination of variable frequency drives (VFDs) that heated water automatically based on demand.

Dan 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. We also monitor the maintenance of the system to make sure there are no problems that might affect energy efficiency if failures go undetected.