Decarbonization of New York City’s public housing portfolio advanced with one of the Northeast’s largest residential geothermal installations—a $64-million, all-electric system serving 17 buildings. The project replaced centralized fossil-fuel heating and hot-water systems with a closed-loop geothermal network, using borefields drilled 500 ft into bedrock to feed high-efficiency heat pumps delivering year-round domestic hot water. The initiative supports compliance with the city’s Local Law 97, which targets a 40% reduction in carbon emissions by 2030 and 85% by mid-century.

Richard Thomas, vice president–North America region at CSA Group, says inefficient existing infrastructure and undocumented leaks complicated efforts to “right size” the system. After assessing actual hot-water demand and correcting inefficiencies, the team established “reasonable and appropriate usage within the buildings, allowing the design to move quickly forward and resulted in unprecedented performance once installed,” Thomas says.

Photo courtesy Adams European

Encountering additional hidden leaks while tying into legacy piping prompted the team to deploy advanced leak-detection tools and targeted repairs. Customized 30-ton dual-compressor heat pump units were installed to consistently supply water above 140° F. Independent verification confirmed a coefficient of performance roughly double typical efficiency at those temperatures.

Work was carefully phased to maintain access and safety across the fully occupied complex. Borehole drilling and mechanical upgrades were sequenced to minimize noise and vibration, with real-time monitoring and continuous resident coordination led by a dedicated community liaison.

Despite utility coordination challenges—including extensive power upgrade reviews—the project finished ahead of schedule and within budget, completing two years of work with zero recordable incidents.

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