Heat Pumps for Mid-Size Multifamily: Session Two of the Heat Pump Solutions Lab

By Jay Fox

This summer, the Reimagine Buildings Collective has produced two sessions as part of the Heat Pump Solutions Lab. The first, held on July 29, covered small buildings and produced a running list of the things that go sideways in single-family Passive Houses, along with the fixes practitioners have already paid for once. The second, on August 12, moved up a weight class to mid-size multifamily and light commercial, where systems grow in size and complexity. As with the first session, the goal is to give experts an opportunity to talk about real-world solutions, give listeners practical and actionable advice, and allow for enough back-and-forth so nobody logs off carrying the same question they arrived with.

If you want to check out our coverage of the first session, you can follow the link here. Below, we’ll run through the presentations and summarize some of the conversations that followed during the Q&A portions of the event. Presenters included:

• Cameron Caja of Positive Energy,

• Galen Staengl of Staengl Engineering,

• Jordan Bonomo of the New York City Housing Authority (NYCHA), and

• Louis Pfundstein of Ice Air.

Each brought a project, and each brought the part of it that did not go according to plan.

Caja noted that part of the reason why air-to-water systems are so compelling is because of their distribution systems. It takes 62.4 BTUs to raise a cubic foot of water one degree and 0.018 BTUs to do the same to a cubic foot of air. The twelve-inch duct you were going to run through a firewall becomes a three-quarter-inch piece of PEX, which is square footage handed back to the occupants and a long list of fire-rating headaches that never gets written. This is only the tip of the iceberg when it comes to the benefits of using AWHPs; more can be found on a slide taken from Caja’s presentation (below).

Bringing Installers on Board

These are sophisticated systems, but they’re not overly complicated or reliant on exotic components. As he explained, Positive Energy has designed AWHP systems in high-performance single-family and mid-size multifamily buildings in the heart of Texas.

However, he said that he frequently faces an uphill battle whenever his firm is working on a project outside of California or the Northeast. When Positive Energy hands the drawings to a contractor outside of one of these areas, the number that comes back is one Caja described as enough to make your mother blush. “They're going to demand half of the project budget just to install this system,” he said.

Positive Energy recognized that these quotes were not meant to be thought of as a real price; they were refusals with a dollar sign attached. What Caja and the folks from Positive Energy didn’t understand was the reason behind the reluctance, so they started interviewing installers, including the ones who said no.

What they found was less technical than cultural. Electrification has been absorbed into the culture war, and for a meaningful share of contractors even dancing around the word triggers a reaction before any system gets described. Leading with low-GWP refrigerants does not open that door; talking about decarbonizing anything only makes it worse; and saying the phrase “climate change” aloud is seen as a direct provocation. To avoid this kind of confrontation or culture war skirmish, it’s best to focus on the other benefits of these systems: occupant comfort, improved performance, and the kind of elegant engineering that people who build things for a living can really appreciate.

Caja noted that political differences represent a common reason why contractors are disinclined to install these systems. There are others. As he explained, the industry runs on high-volume, fixed-fee work, and it is organized to eliminate friction. Changing to a new system means educating the client, coordinating a plumber alongside an HVAC contractor, and running load calculations that much of the industry regards as unnecessary. The installers who say yes, in Caja’s telling, are self-motivated small business owners who intend to be early adopters to give them an edge.

Parity in Perinton

Staengl spoke about Midvale Commons, which was a Round Two winner of the New York State Energy Research and Development Authority’s Buildings of Excellence Competition (note: it originally had the more prosaic name of Baird Road Apartments). Located in Perinton, New York, the building contains 76 units of senior housing and spans just over 76,000 square feet.

The project had a very tight budget, and it unfortunately ran into delays due to funding challenges as the COVID pandemic was wreaking havoc around the world, including on global supply chains. The finished design remained stalled for a year and a half. By the time Christa Construction picked it back up, inflation had eaten whatever cushion the award from NYSERDA had afforded the team. The goal became playing it safe to limit the possibility of cost overruns while still working within a Passive House framework.

One of the largest items on the budgetary chopping block was the heat pump system. The mechanical subcontractor’s first read was that heat pumps would run fifty percent above the gas-fired system they were used to installing. Instead, it landed at parity.

Staengl credits the cost reduction to several factors. As he explained, the team designed around a slim vertical indoor unit set into a thickened wall between the living room and the bedroom of each one-bedroom apartment. This cut down on the amount of ductwork needed and meant that no equipment ended up eating usable floor area. As an added bonus, everything is now serviceable via one access panel.

Another crucial aspect of the design is that the outdoor condenser units were installed on the wall directly outside each apartment rather than up on the roof. Americans generally decline to do this, as Staengl put it, “because we don’t want to look at those things.” The squeamishness is expensive. Wall mounting shortened the refrigerant line sets and spared the owner from running wire and refrigerant upstairs to meter tenant energy use. As an added bonus, it reduces the amount of refrigerant in the building and could be a useful strategy when designing mechanical systems with A2L refrigerants. (As Heather McKinstry of Dattner Architects explained in the previous session, many of the new regulations that make the use of A2L refrigerants more cumbersome only apply when lines cross between floors.)

Another benefit of mounting the units on the exterior is that it spared the project from flattening a section of roof for dunnage. The move almost certainly cut costs, but Staengl said he was not clear if the savings were properly accounted for.

The Promise of Window Units

The number of people living in NYCHA housing is larger than the population of Miami. The portfolio contains approximately 2,400 buildings. Under Local Law 97, NYCHA has to cut portfolio emissions 80 percent by 2050, and 93 percent of its space heat arrives as steam from central plants. There are more than 100,000 occupied apartments, vacancy runs under one percent, and somebody is living in every one of them while the work happens. To add insult to injury, NYCHA has been underfunded for decades and now needs $70 billion in capital improvements.

As one can imagine, retrofitting all these units will require a decades-long and truly herculean effort.

NYCHA’s first move was to industrialize the retrofits through an Energiesprong-style approach that was developed through NYSERDA’s RetrofitNY program, which launched in the late 2010s. This would have involved the use of prefabricated panels to speed up the retrofit process and to minimize tenant disruptions. Unfortunately, the industry was not mature enough to propose cost-effective retrofit solutions at the time, so the idea was scrapped.

NYCHA’s second move was to pilot a full-building VRF conversion on a building in Manhattan’s Upper West Side. The retrofit meant core drilling through occupied floors and long runs of refrigerant. Midway through that job, a rep handed Bonomo an Innova unit (then known as Ephoca) built to go through a wall. NYCHA had no appetite for punching holes through old walls full of hazardous materials, so the team tried a window in the superintendent’s office. They fabricated a plenum that went through the bottom of a double-hung window, watched it leak faster than they could seal it, and finally just put the unit through the window. It worked.

The idea helped to inspire the Clean Heat for All Challenge, issued with the New York Power Authority and NYSERDA in late 2021. They wanted private companies to create what was essentially a saddle heat pump with a low profile that could go through the window, run on 120V, provide 9,000 BTUs, and be installed by unskilled labor within two hours. The units would also need to have internal condensate disposal systems. The reward was serious, Bonomo said. Any firm that met the specs would walk away with a contract for 20,000 units.

Two firms, Midea and Gradient, were awarded the contract.

At Woodside Houses in Queens, in-house maintenance staff pulled the radiators and converted 24 apartments in eight days. In contrast, the split systems NYCHA had been installing were taking roughly eight days per apartment. The energy savings have been substantial (over eighty percent), and the pilot is reporting cost savings on heating of more than fifty percent (see Clean Heat for All, Woodside Houses Pilot). Those savings were achieved without upgrades to the envelope. Additionally, the tenants no longer have to rely on outdated window air conditioners for cooling, and they have some control over their indoor environment in the winter. Prior to the upgrades, their only option was having the radiator on or off and the window open or closed.

According to Bonomo, the next generation of units is installed within an INTUS triple-pane casement window. The units have a custom gasketed sleeve at the bottom, so the resident can open and close the window above the heat pump without disturbing the seal.

Bonomo noted that there are some issues still to address. The new units have pushed some rooms out of compliance with New York State’s light-and-air minimums. Another challenge is that maintenance staff will need to be trained to service these systems. Relatedly, maintenance scheduling and access will need to be altered. Rather than fixing a central steam plant, staff will need to regularly enter apartments to clean air and condensate filters.

Sealing the Gap

Passive House construction and packaged terminal heat pumps (PTHPs) do not sound like an ideal pair, especially in multifamily buildings. Beyond a robust enclosure and continuous insulation, Passive House construction demands an exceptional level of airtightness. Meanwhile, PTHPs need direct access to the exterior, necessarily requiring numerous holes to be poked in the enclosure.

However, Ice Air, an original equipment manufacturer with a line of PTHPs, recognized the writing on the wall several years ago. Passive House was growing and continues to grow in popularity, and their standard PTHP needs a wall opening 42 inches by 16 inches. Without major changes, anyone working on a project where airtightness was a priority, let alone a Passive House project, was not going to want to work with them.

To solve the problem, Ice Air started by insulating the chassis, which they had already done to cut sound transfer for buildings near the elevated trains in Queens, and then set to work improving their airtightness. They worked with Stephen Winter Associates and kept testing units in the shop and coming back short. However, after upgrading every gasket and seal, including around the electrical passing through the firewall between the indoor and outdoor sections, they finally designed a product that could hit airtightness goals in ideal settings.

The next hurdle was taking the units out of the lab and learning how to install them in the real world. These challenges were addressed at two projects in Brooklyn: Clarkson Estates and Livonia C3. The former is pursuing Passive House certification. The latter is a winner of Round Three of the Buildings of Excellence Competition that has been Phius design certified. The lessons learned from the field give Ice Air the kind of practical knowledge they need to smooth out installations going forward.

The Road Ahead

The third and final installment of the Heat Pump Solutions Lab on August 26 takes on large buildings and high-rises, and the three sessions together will shape the program for the public Heat Pump Solutions Summit that Passive House Accelerator will host in October. Sessions are open to any Collective member, and slides, recordings, and transcripts can be found in the Heat Pump Solutions Lab space within the Reimagine Buildings Collective.

What made this session worth the two hours was not the slides. It was the conversations between speakers and audience, the active chat, and the community’s willingness to come together to solve problems. As we’ve seen time and time again at the Accelerator and especially in the Collective, if you have a problem, someone else in the community has likely encountered it and figured out an answer.