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Retrofitting Residential

Multi-Family Homes Best Place To Start Efficiency Upgrades

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Open windows in January are a just one sign of the energy inefficiencies that plague many multifamily buildings in urban areas.

Studies of multi-family structures show wide variations in energy consumption per square foot with the least efficient buildings using seven times more energy than the most efficient. “These wide fluctuations mean many buildings are candidates for energy efficiency upgrades that can reduce costs and improve cash flow,” explains Andrew Padian, vice president for energy initiatives, The Community Preservation Corporation, New York.

At Jennings Hall at 260 Powers Street in Brooklyn, a steam boiler supplied steam to the 54-unit west wing and hot water to the newer 100-unit east wing via a heat exchanger. The heating plants for the two wings were separated by getting an unused, existing 90 hp steam boiler up and running again to make hot water for the east wing. The original boiler now only supplies the west wing.
Photo courtesy of Steven Winter Associates
At Jennings Hall at 260 Powers Street in Brooklyn, a steam boiler supplied steam to the 54-unit west wing and hot water to the newer 100-unit east wing via a heat exchanger. The heating plants for the two wings were separated by getting an unused, existing 90 hp steam boiler up and running again to make hot water for the east wing. The original boiler now only supplies the west wing.
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Energy audits of multifamily buildings, now mandated in New York City for structures over 50,000-sq.-ft., typically identify a common set of cost-effective retrofits and operational modifications to reduce energy consumption. “This not about green roofs and solar panels,” Padian says. “It is about taking an existing building and making it work right.”

Basic Retrofit Strategies Air sealing tops everyone’s list of retrofits with a quick payback. “We go into buildings and see a tremendous amount of air leakage,” says Alex von Braun, senior commissioning engineer, Viridan Energy & Environmental, New York. “The taller the building, the bigger is the problem.”

During cold weather, rising warm air draws in cold air through cracks and holes. Sources of leaks include windows, doors and pipe penetrations. “On a cold day you can feel air flowing in and that is money flowing out of the building,” von Braun says.

Air leaking through cracks and holes can result in as much heat loss in a building as the combined effects of heat loss through walls, windows and roofs, explains Marc Zuluaga, senior engineer, Steven Winter Associates, Norwalk, Conn.

At the nine-story, 99-unit Echo Apartments at 1050 Amsterdam Avenue, New York, air sealing focused on leaks around lower level bulkhead and entrance doors and at the top of the building. “The top of the stairwell is vented per fire code, so there is basically a big hole,” Zuluaga says. The vent was retrofitted with a motorized damper that opens only with a signal from the building’s smoke detector system, otherwise it stays closed.

Heating SystemsHeat distribution problems, common in multifamily buildings, are often corrected with heating controls.

Echo Apartments retrofitted all its units with thermostatic radiator valves (TRV) to control the hot water distribution system. A TRV (costing $300-400) turns off water flow to the apartment once it reaches a specified temperature. Locking pins prevent tenants from tampering with TRV temperature settings.

Employing TRVs with two pipe steam is more expensive. “With hot water you have one valve per apartment because the baseboards are in series,” Zuluaga says. “With steam you usually need one valve per radiator.”

Another option for two pipe steam, orifice plates, was installed by Gifford Fuel Savings, New York, at the 54-unit west wing of Jennings Hall at 260 Power Street, Brooklyn. The orifices regulate and balance the systems so that the risers fill with steam instantly, allowing steam to flow into all radiators simultaneously.

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