By Jay Fox

Last week’s Reimagine Buildings: Multifamily brought together hundreds of folks from the architecture, engineering, and construction (AEC) industry and beyond to learn about the advances of Passive House strategies as they apply to multifamily construction. The four-hour virtual conference featured practitioners and researchers who provided real-world expertise and actionable tips for designing and building multifamily projects that meet Passive House standards, as well as some of the new technologies that are helping to decarbonize these buildings.

Multifamily Housing By the Numbers

Multifamily housing includes 45 million condos, apartments, and townhouses across the nation. As Passive House Accelerator Director Zack Semke noted during the first hour of last week’s event, that translates into roughly one-third of the United States’ housing stock.

No surprise, each region and even each state has a unique housing stock, with some having significantly more multifamily housing than others. Multifamily housing is a significant part of building stock in Northeast states like New York (52.8%), Massachusetts (42.8%), and Rhode Island (39.7%), but is only a fraction of that in rural states like West Virginia (14.6%), Idaho (17.0%), and Mississippi (17.1%). At the national level, multifamily building has historically played a secondary role when compared to detached single-family housing, as shown in Figure 1.

Figure 1 also shows that this is changing. The share of new housing units authorized in multifamily structures has trended generally upwards since hitting a nadir in the early 1990s. Between 2009 and 2015, the share of new housing authorizations for multifamily units rose from 24.3% to 41.1% and has been on a bit of a rollercoaster ride ever since (see Figure 2). As of 2025, the rate was 36.2%.

Unsurprisingly, many states are leading the way and authorizing more housing units in multifamily structures than in single family. In 2025, the share was over 50% in six states, including New York (77.5%), Connecticut (64.1%), Massachusetts (60.8%), New Jersey (57.6%), Alaska (56.8%), and Rhode Island (53%). As Figure 3 shows, most states without major urban centers produced far fewer multifamily units, though some notable outliers include Nebraska (46%), South Dakota (45.9%), and Montana (43.4%).

Quiet Buildings, Healthy Buildings

All that out of the way, it’s time to get to the event. The first hour launched into an in-depth look at two major multifamily projects pursuing Passive House certification: Magnolia Gardens in New York City and Bunker Hill Housing Development in Boston.

Urban Architectural Initiatives Partner Jorge Chang described the former, which is an 89,000-ft² development steps from Downtown Flushing that has recently opened and creates 90 units of transitional housing for families experiencing housing instability. Co-developed by Asian Americans for Equality and Urban Resource Institute, two non-profits that have a long history of assisting New York City’s Asian American community, the project takes into account cultural considerations while also being heavily influenced by trauma-informed design (TID).

A key component of TID is creating a sense of autonomy and control. The design team quickly recognized that giving occupants the ability to reclaim that sense of control was going to be difficult, however, because of noise. New York City is not known for being peaceful, of course, but the site is in a particularly congested part of Queens that is not only close to Downtown Flushing but also major transit hubs like the terminus of the 7 line, the Long Island Railroad’s Flushing – Main Street station, and LaGuardia Airport.

Building to Passive House standards resolved this issue because passive buildings are airtight, well-insulated, and outfitted with high-performance windows. Consequently, they mitigate external noise, creating serene indoor spaces even in the midst of New York City. Passive House also provides a steady stream of fresh and filtered air with mechanical ventilation. Consequently, occupants of Magnolia House will have a quiet, peaceful, and healthy space to call home.

Chang’s presentation was followed by Leggat McCall Properties Senior Project Manager Nick Nigro, who described the redevelopment of Bunker Hill, a sprawling, seven-acre development located in Boston’s oldest neighborhood, Charlestown. Since being built in the 1940s, Bunker Hill has consisted of just over 1,000 units spread across 42 three-story walkups. Those buildings will be torn down, and in their place will arise 15 larger buildings ranging from six to ten stories that contain a total of approximately 2,700 units. Far more impressively, each building will be built to Passive House standards and be made from prefabricated cross laminated timber (CLT) components.

The first building, known as Stellata, was recently completed in just 16 months and holds 102 affordable units within 120,000 gross square feet. While an article by Andrew Steingiser published on the Accelerator delves into some of the technical details, Nigro was able to talk about the construction of the project, which was only just beginning when Steingiser’s article was published in early 2025. Nigro noted that vertical erection took only four months from the time the foundation was completed until they topped out. "Another neat stat," Nigro notes, "is that the entire building was erected by only six carpenters plus the crane operator."

The reduced onsite labor force is part of the reason why Nigro and Leggat McCall believes that this kind of construction, even when built to Passive House standards, will compete at the same cost level of a five over one stick construction.

While this is good news, what makes the project so monumental is that the team will only get better at assembling the prefabricated CLT components. “You don’t know what you don’t know until you try to put it together,” Nigro said. Consequently, Leggat McCall anticipates seeing a steady decline in costs as the team becomes more accustomed to assembling the prefabricated pieces and gets more opportunities to troubleshoot in the real world.

Earlier Is Better

While the first hour of the event looked at specific projects, cohost and Dattner Architects Director of Sustainability and Associate Principal Shefali Sanghvi explained that the focus of the second hour was on the practical decisions that shape buildings. The hour included sessions by speakers:

• Kia Weatherspoon (Determined by Design, Founder and President)

• Shannon Pendelton (Sanderson Sustainable Design, Principal CPHC)

• Ryan Abendroth (Build Zero Consulting, Co-Founder)

• Stefan Goebel (Build Zero Consulting, Co-Founder & Principal)

• Galen Staengl (Staengl Engineering, President)

• Ed May (BLDGTYP, Partner)

If there is a lesson that project teams repeatedly say they’ve learned after going through the challenges of certifying through Phius or the Passive House Institute, it is to assemble the team early and to have that team meet often. This includes the architect, MEP and structural engineers, GC, interior designer, and consultants responsible for energy modeling, building enclosure, and Passive House certification. More than creating team cohesion, bringing more firms on at an earlier point in the project can save money and prevent delays. After all, every decision that needs to be revised becomes harder and more expensive to revisit as time goes on. If an architect has not left sufficient room for ductwork or failed to consider how the maintenance team will access equipment, it is far easier and cheaper to make amendments on paper rather than once the drywall is up.

As Witherspoon said, getting perspective from the interior designer is crucial, too. The idea of creating something beautiful can take a backseat to the need to hit performance goals or comply with building codes or consider the durability of a material, but these priorities are rarely fighting against one another. Moreover, as Witherspoon memorably said, “Beauty is a part of wellness and joy.” Thoughtful and empathetic design deserves a seat at the table.

Unfortunately, the results of ignoring aesthetics can result in long-term issues that will ultimately affect residents’ ability to fully enjoy their home. As an example, Witherspoon noted that a project in Boston may have had lovely fixtures and finishes, but the corridors were 7.5 feet tall. While this is above the minimum height for both habitable and non-habitable spaces, it can still feel constrictive. An interior designer would have known to look for that issue and, had they been brought in early enough, they would have been able to propose a cost-effective solution.

Whether due to an engineering issue or an aesthetic one, reactive design is always more difficult and expensive.

Spotlight on NYSERDA and the UK

Hour three included two sessions. In the first, Passive House Accelerator Founder and Ingui Architecture President Michael Ingui had a chat with Magnuson Architecture and Planning Associate Principal & Director of Sustainability Sara Bayer. Bayer discussed how participation in the New York State Energy Research and Development Authority (NYSERDA) Buildings of Excellence Early Design Support Program has aided their research into high-performance buildings, particularly at Carmen Villegas & Casita Park Apartments and Sol on Park. More than just gaining the ability to perform feasibility studies for individual projects, Bayer noted that NYSERDA has allowed medium-size firms like MAP to build capacity and to better understand the costs and logistics of decarbonization in new construction.

The numbers are impressive. Callow said that his team alone is currently working on 9,500 Passive House units, which are either under construction or in varying stages of design. This is equivalent to 5% of the total units that will be completed in the U.K. this year.

“I cannot emphasize enough what a complete transformation that is,” he said.

The State of Passive House in North America

The final hour was a panel led by RDH Principal, Passive House Specialist, and Service Lead Marine Sanchez. She was later joined by co-moderator New York Passive House Executive Director and ZAZNRG Founder and Principal Carmel Pratt. Panelists included:

• Michelle Apigian (ICON Architecture, Managing Principal)

• Heather McKinstry (Dattner Architects, Senior Associate and Studio Director)

• Jessica Morrissey (NEI General Contracting, Associate Director of Preconstruction Services)

• Crystal Ng (Curtis + Ginsberg Architects, Senior Associate and Director of Sustainability)

There was no shortage of wisdom shared by the panel members, and their invaluable advice tended to center of practical steps to make the Passive House journey less arduous. As Sanchez noted, Passive House is no longer about vision; it’s about execution, and success comes as a result of teamwork and cooperation. For example, both Sanchez and Morrissey advised getting the entire team, including the trades, up to speed on what Passive House means to avoid scope gaps.

Apigian added that this collaborative effort extends to the maintenance crews once the building is complete. One of her pieces of advice was to have maintenance workers regularly check if the ERVs are functioning as intended because occupants will notice if their heating or cooling systems aren’t working right but may not recognize a lack of adequate ventilation. "The fresh air is much more subtle," she said.

One of the most enduring discussions from the panel concerned the challenge of getting others who are lukewarm on Passive House to take the plunge. True, passive buildings are more durable, healthy, comfortable, and valuable than buildings that just meet code, but developers and owners often scoff at the additional upfront costs. Meanwhile, GCs in regions where Passive House has yet to catch on often upcharge by huge amounts because they simply have no idea what they’re getting into.

McKinstry recommended having them speak with others who have built or overseen the construction of a Passive House. She also recommended they visit one to experience it. Apigian noted that this will allow either GCs or developers to understand the level of quality and durability they are paying for.

These pieces of advice also serve as a reminder of something that Emily Mottram said during an AMA with Michael Ingui at the end of 2025. Deciding against high-performance building is not cost savings; it’s cost deferment, she said. You will eventually have to build to a higher standard, you will have to replace components with limited durability, you will watch your utility bills inch higher as your buildings systems degrade. Building to Passive House standards avoids those problems and ensures residents live in a healthy, comfortable, and resilient home.

For multifamily owners, it's an investment that results in a less problematic and more valuable building.

Top image of Parkview at Terwilliger Plaza in Portland, Oregon. Courtesy of David Papazian Photography