Manhattan Co-op Addresses Radiator Noise and Achieves Energy Savings in One Move

A Manhattan co-op has solved two problems in one stroke by taking steps to silence its noisy steam radiators and, in the process, reap savings on its energy bills. And shareholders long frustrated by the banging and clanging are breathing a sigh of relief.

“The building’s steam heat system was very very old,” says Ramez Afify, principal of E4P Consulting Engineering, the firm brought in to figure out how to reduce the radiator noise. The eight-story, eight-unit co-op has an oil-fired boiler with steam distributed in a two-pipe system. This means steam is delivered to radiators in one pipe and the condensed water returns to the boiler in another pipe. 

Two-pipe systems have steam traps on the radiators to discharge the liquid that condenses in the pipes. They are necessary to prevent banging, which can occur when the heat starts up and the steam hits the liquid condensate. What surprised Afify was that the co-op had a two-pipe system but no steam traps, which meant the condensate wasn’t being discharged. “The building’s steam system was installed before the invention of steam traps,” he says. 

Renovations in individual apartments had contributed to the noise problem, because some contractors who noticed the two-pipe system added the missing steam traps. Others had seen the absence of steam traps, assumed it was a one-pipe system and had cut or sealed the second pipe on the radiator. This lack of consistency throughout the building made the banging worse. “It sounds like metal against metal every few seconds,” Afify says. 

The first step in reducing the radiator noise was to convert the system into a two-pipe system with steam traps. Steam traps had, at one point, been added near the boiler in the basement, but it was clear they were not working and needed to be replaced. Steam traps were also needed on individual radiators. Because each radiator had two valves — the twisting mechanism that allows you to control how much heat you want your radiator to give out — one of the valves was replaced with a steam trap.

The next step was to remove the radiator air vents and have a central vent near the boiler. The old system had air vents on each radiator, which is in fact a characteristic of a one-pipe system. Air in a steam system can slow the flow of steam and create noise. “Removing the vents from each radiator allows the system to operate as a true two-pipe system and avoids confusing future contractors as to what type of steam system is in the building,” Afify explains.

At that point, co-op residents could only hear “acceptable sounds of water flowing,” Afify says. But having achieved this much, shareholders wanted to make the system even quieter. It turns out the boiler was not operating at optimum pressure: It was functioning at 5 psi (pounds per square inch) and the goal was to get it under 3 psi. “The pressure in a steam boiler is similar to blood pressure in the body,” Afify says. “It’s better for the system to operate at lower pressure, which is more efficient, and less noise is produced and more energy saved.” The pressure was lowered in phases, with adjustments made using a pressuretrol, a control that sets when the boiler should begin and end firing based on stream pressure, until it was below 3 psi.

The co-op tapped into reserve funds to pay for the $50,000 project. However, budget constraints meant the radiator repairs were only carried out on apartments at the front of the building, where shareholders had the most noise complaints. When the co-op has the money, work will be carried out in the back of the building. When completed, the retooling is expected to generate winter savings of between 10-15% for the building.