Pilot light: HDFC co-op pioneers a new strategy for air-source heat pumps

To replace the boiler, or not replace the boiler — that was the ques­tion, for the share­holders of the ten units of a 1926 walkup building on the Upper West Side of Manhattan back in 2017 and 2018.

Their #2 heating oil-fired boiler had sent steam rattling and hissing up to cast-iron radi­a­tors in the apart­ments on the building’s five floors for 40 years, leaving resi­dents without the ability to control the temper­a­ture in their own spaces. A consul­tant hired to do a capital needs assess­ment for the building had recom­mended it be retired. 

Some share­holders, worried that the boiler could give out at any moment, thought the co-op should imme­di­ately get a new gas-fired boiler. But Lisa Harrison, a third-floor resi­dent and an envi­ron­mental activist who had fought the buildout of gas pipelines in New York State, was opposed to an expen­sive invest­ment that would lock the building into fossil fuels for years to come. If the share­holders were going to make a change, Harrison felt it should be ​“future-oriented.”

Her search for a climate-friendly alter­na­tive to the status quo led her to Tom Sahagian, an expert in multi­family energy effi­ciency who happened to be looking for a building for a pilot project that would show­case the prac­tical bene­fits of heat pumps. They joined forces and, working with a manu­fac­turer that spon­sored the pilot, the share­holders had heat pumps installed in 2020.

The pilot was a stroke of good luck for the low-to-moderate income share­holders, but over the project’s two years, they also devel­oped their own resourceful solu­tions and became experts along the way. In every­thing from the place­ment of equip­ment like air pump units to the elec­trical power of the building, Sahagian and the resi­dents worked together to develop home-grown solu­tions that managed to increase comfort while cutting expenses and lowering carbon emissions.

Now, ​“Everyone loves the heat pumps,” Harrison said.

The Challenge

There’s a reason Harrison and her fellow share­holders leaped at the chance to partic­i­pate in the pilot project: Their building is one of the 1,100+ Housing Development Fund Corporation (HDFC) coop­er­a­tives for low- and moderate-income New Yorkers, and they had only modest resources at their disposal. 

The HDFC program, which orig­i­nated in the 1970s, essen­tially let tenants in certain City-owned build­ings buy their apart­ments for as little as $250 each, on the condi­tion that they work together to main­tain and improve the build­ings through ​“sweat equity.” 

Harrison wasn’t living in her building when it became an HDFC co-op in 1983 — she moved into her 820-square-foot, two-bedroom rail­road flat with her then-6-year-old son in 1998. But she seems to possess some of the scrappy, can-do spirit of the early HDFC tenants. When the boiler ques­tion came up, she was trea­surer of the co-op, and had recently retired from a job as a tech­nical writer for a company in the banking industry.

Harrison and her fellow share­holders had already been working to increase energy effi­ciency and lower building costs. They had swapped out incan­des­cent and fluo­res­cent lighting for LEDs with motion sensors in the public areas of the building and installed new windows. Shareholders paid for that project with money from their reserve fund and then replen­ished the fund by levying an assess­ment on them­selves. But replacing the boiler would be a much more expen­sive under­taking, and would require the building to take out a loan, trig­gering yet another assess­ment. Heat pumps also held out the possi­bility of giving tenants control over the temper­a­ture in their own living spaces. Along with the energy savings and the possi­bility of not needing window air condi­tioners, ​“comfort was a driving issue,” Harrison said.

The Roadmap

Through their social networks, Harrison got put in touch with Sahagian, who was looking for a building to test the pilot idea he had cooked up with a friend named Ian Shapiro. Shapiro is the founder of an engi­neering company in Ithaca, N.Y. called Taitem, which stands for ​“Technology As If The Earth Mattered.” They felt it would be easier to convince multi­family build­ings to give heat pumps a shot if they could prove that the elec­trical devices worked well during New York’s cold winters, and still offered all the other bene­fits that heat pumps regu­larly tout: reducing green­house gas emis­sions, enhancing the comfort of the building, and, ideally, saving people money.

“There were no exam­ples out there that anyone could point to that say, ​‘these people did this, it cost this, they saved that,’” Sahagian said.

All they needed was a building, and Harrison’s walkup seemed to fit the bill because it is typical of much of New York’s housing stock: A pre-war, brick building with an oil-fired boiler that provides space heat and hot water. (Residents used their own window ACs to cool their apart­ments in summer.)

Sahagian and Taitem had already brought Daikin U.S. Corporation, a leading HVAC manu­fac­turer, onto the project. Daikin agreed to donate ten air-source, multi-split heat pumps, one per apart­ment. Daikin would also cover the costs of project design (by Taitem) and instal­la­tion (by a contractor) — esti­mated at a total cost of about $20,000 per apart­ment before incen­tives, said Jon Hacker, then Daikin’s Energy Efficiency Business Development Manager.

Some share­holders didn’t know much about heat pumps, but the idea of a single system that would both heat and cool their apart­ments was appealing. The share­holders agreed to a pilot that would last for two years, allowing ample time for moni­toring after the heat pumps were installed.

Sahagian and Shapiro lined up one last partic­i­pant in the pilot: They wanted rigorous moni­toring of the project, so they obtained grant funding from the New York State Energy Research & Development Authority (NYSERDA). With that extra funding, Taitem could install elec­tricity moni­tors in the building and gather pre- and post-project data for analysis. 

The Project

The pilot was designed to show that air-source heat pumps can func­tion in New York’s climate, that they can work for a variety of building types, and that they can be installed at moderate cost.

Even with below-freezing temper­a­tures during New York’s cold winters, air-source heat pumps work by extracting heat from the air outside a building and moving it inside. In the summer, the system works in reverse, taking the thermal energy that has built up inside a building and moving it outside.

Each heat pump consists of a boxy outdoor unit that pulls in heat from the outdoor air and a handful of indoor units to transfer heat to the apart­ments indoors. The project designers’ initial assump­tion was that the outdoor units all had to go on the roof, which is how heat pumps are usually installed — but this would have required a pricey instal­la­tion of supportive infra­struc­ture. Harrison’s building ended up placing only four of the ten units on the roof, while four others were hung on the lower, stone-and-mortar portion of the side walls, and two in the middle of the rear wall, next to the fire escape. The pilot showed that it’s possible for heat pumps to be placed in any number of loca­tions along a building’s exte­rior, depending on its archi­tec­ture, avail­able space, and prox­imity to neigh­boring buildings. 

Meanwhile, power and refrig­erant lines snake from the outdoor units through small holes drilled in exte­rior walls to the indoor units. Some of the lines are enclosed in flat­tened, white plastic tubing called ​“line hide,” which is visible on the rear and one side of the building. ​“Sometimes saving the planet is ugly,” Sahagian says of the setup. But nothing mars the building’s digni­fied façade.

Another common assump­tion about heat pumps that the pilot dispelled is that elec­trical rewiring is a prereq­ui­site. ​“This building is living proof that it’s not always true,” Sahagian said.

The co-op was also able to avoid a costly rewiring. The 40-amp breakers on the elec­trical meters in the base­ment were swapped out for 50-amp breakers, which can carry more elec­tricity. But Sahagian deemed the building’s existing #8 elec­trical wires suffi­cient to handle the added elec­trical load from the heat pumps — and an outside engi­neer brought in to make an inde­pen­dent assess­ment agreed. ​“In the four and a half years we’ve had this system, I don’t think we’ve popped a breaker once,” Sahagian said.

Installation took place in summer 2020, with the contractor tack­ling one apart­ment at a time. Shareholders opted to move out for two or three days during instal­la­tion. Sahagian, whom Taitem paid a modest fee to keep tabs on every­thing, hunkered down at Harrison’s farm-style dining table prac­ti­cally daily, trou­bleshooting when needed.

When the dust was all vacu­umed up and kinks in the system worked out, the heat pumps worked as promised. And there was a bonus: With the noise from radi­a­tors and window ACs gone, the building became a more peaceful place. 

The share­holders never did replace the old boiler, which is still used to produce the building’s hot water. But because the boiler doesn’t have to work so hard anymore, oil consump­tion fell from 4,000 gallons per year to about 1,700 gallons. 

Meanwhile, the building’s green­house gas (GHG) emis­sions declined 58 percent for heat and hot water (and 48 percent for the building as a whole, taking into account things like lighting and plug-in appli­ances), according to data Taitem gath­ered. Energy costs for heat and hot water dropped nearly 11 percent, from about $11,900 annu­ally to about $10,600.

There was a shift, however, in how energy expenses are felt. Shareholders’ monthly Consolidated Edison bills have gone up, since they are each paying directly for their own elec­tricity-powered heating now, and because of Con Ed rate hikes. The share­holders initially had ​“sticker shock” when they saw their Con Ed bills, Harrison says, but people have adjusted to the new normal by now.

Because they now pay for their own heat, the share­holders could have reduced their monthly main­te­nance fees to compen­sate for their higher Con Ed bills. Instead, they decided to sock away the extra money to build up their reserve fund for future projects — the roof needs work, and one day, Harrison hopes, the building will have a heat pump for the hot water.

The walkup’s square footage is far below the threshold that trig­gers Local Law 97 (LL97) require­ments. But even so, the building has a head start on embracing a clean energy future.

“We are way ahead of the curve,” Harrison said.