By Jay Fox

Michael Browne was leaving Leefort Terrace one afternoon when rain began to fall on Salem. The sun was still out, and he knew what Mother Nature had in store for him if he was patient. He made his way around Collins Cove, past tidal mud flats wet enough to pass for open water, and caught sight of what he’d set out to capture: a rainbow. It seemed to land on the roof of the recently completed building. Behind the building rose the stacks of the natural gas plant a few blocks away. RDH Building Science, where Browne works as a HERS Rater and Certified Phius Verifier, later ran the photo as a full-page ad in the program for the building's NESEA Pro Tour.

The picture he still intends to capture will be harder to time. The cranes that service offshore wind turbines work out of the same harbor, and from the right angle their barges stand taller than the gas plant’s stack. Browne imagines all of it in one frame: the cranes towering over the gas plant, then Leefort Terrace, and then the flats, ideally at high tide, with the water rising toward the building’s edge. Even for someone unfamiliar with the area, the theme behind both compositions is transformation and the ascendancy of cleaner, greener technologies.

Both images also speak to Massachusetts’ success in making scenes like this commonplace, particularly with respect to high-performance buildings. The industry has shifted dramatically in just a few years, and the principles of Passive House have ceased to be exotic to architects, GCs, and other people within the construction industry. As a result, Massachusetts is now leading the country in Passive House construction.

Leefort Terrace: Reframing Business as Usual

The Salem Housing Authority (SHA) issued a Request for Proposal (RFP) for the redevelopment of Leefort Terrace in early 2020. At the time, the 3.2-acre site at the base of Salem Neck contained 50 one-bedroom apartments for seniors and individuals with disabilities. The garden-style buildings dated to the late 1950s. None of the units were accessible or adaptable, none of the buildings were elevated despite sitting in a coastal floodplain, and the buildings were considered too obsolete for a deep energy retrofit.

Beacon Communities was selected as the development partner later that year, and they secured a 99-year ground lease from the SHA. Demolition followed tenant relocation in 2023, and construction officially began in 2024. Construction wrapped up in April 2026. Approximately two-thirds of the seniors have since returned and taken up residence in the new and improved Leefort Terrace.

The new 124-unit building is four stories tall and includes 1-, 2-, and 3-bedroom units, with a majority of one-bedrooms to accommodate the returning seniors. The additional units are truly affordable, as they are restricted to households earning 50% or less of the area median income. In keeping with passive principles, the design relies on a relatively simple geometry and a modest window-to-wall ratio. The building is U-shaped and organized around a south-facing courtyard with community gardens. It has no balconies, and the only exterior door above grade is roof access for maintenance, because every Passive House–rated door adds cost and another detail to get right.

To better accommodate the senior residents, the new Leefort Terrace has a wellness center with space for visiting care providers, and each floor has its own color palette so residents can tell at a glance whether they've stepped off the elevator on the right level. Even the corridor lighting was tuned for the seniors: occupancy sensors that dim gently instead of plunging into darkness, which can be disorienting.

For all intents and purposes, it is a normal new building in Massachusetts. Hidden beneath that normalcy is more than 15 years of lessons learned, policy initiatives, and upskilling.

Following the Learning Curve

Michelle Apigian, Director of ESG (Environmental, Social, Governance) at ICON Architecture, remembers when nothing about Passive House or even high-performance building was considered routine. Around 2010, a developer came to ICON and said he wanted to build a Passive House on the site of a former rum distillery in South Boston. He had already gone through several architects looking for one who would do it. The team at ICON was curious, Apigian says. “So, we learned together with him.”

Their tutor was a German guidebook with details that looked nothing like anything that was being built in the United States, and their initial design followed what the book said to a T. Then the estimate came in. “It was a couple million dollars over budget,” Apigian recalls.

The project was put on hold as the team reconsidered their approach. During this time, the owner went to a conference where he happened to meet Adam Cohen, a design-build Passive House contractor, and the team brought him on as a consultant. With Cohen’s help, the team redesigned the building to reflect the way Americans actually build: 2x6 framing, with the appropriate amount of continuous exterior insulation (two inches in this case), a rainscreen, and nothing exotic. Cohen modeled it in WUFI and kept telling them the thinner assembly would work. He was ultimately right, and the Distillery North would go on to become the first certified Passive House multifamily building in Massachusetts. Those modest upgrades were enough to reach Passive House cost-effectively, and the result reshaped how ICON talked to clients about the standard. “It’s science,” Apigian says. “It’s math. We can model it.”

ICON’s next project was Finch Cambridge, a 98-unit affordable building constructed for Homeowners Rehab, Inc. Apigian says ICON designed it to Passive House principles with no plan to certify. That changed when the Massachusetts Clean Energy Center (MassCEC) launched its Passive House Design Challenge in 2018. Finch was one of eight funded projects (another was Harbor Village, ICON's third Passive House project), and the incentive covered enough of the testing and verification to make certification possible.

Crucially, MassCEC also required every team to report its cost premium. The results came in between 1.5% and 5%, and both of ICON's projects were under 2%. Once those numbers were public, the state's housing agency (the Executive Office of Housing and Livable Communities) added points to its 2020-2021 Qualified Allocation Plan (QAP) for Passive House. “From that day forward,” Apigian says, “I would bet you that over 75% of the affordable projects in the state are Passive House.”

Since the introduction of Massachusetts’ new stretch code and specialized opt-in code in 2023, which has been adopted on a town-by-town basis, the number of Passive House buildings in the state has skyrocketed. “There’s no multifamily new construction project that isn’t expecting to be a Passive House project,” Apigian says, whether or not the owner plans to certify.

The construction side has also adapted alongside the policy. On Finch, the team worried so much about trades puncturing the air barrier that they posted a large sign at the site: a blue balloon surrounded by saws and nails, with the words Don’t pop the balloon. Apigian admits she has no idea whether it did anything. What did work was using the contractor’s three-week lookahead to identify where Passive House details were about to meet the schedule and then sitting down with the three or four trades involved before the work started to walk through the sequence. This kind of collaboration has become far more common as teams throughout the state have realized you can’t build a Passive House when design and construction remain in separate silos.

From the training side, Browne says he’s noticed that people retain lessons when they understand the intent behind what they’re being asked to do. He starts every trades session by asking who's at the table and what they've done before, and then he explains the reasoning behind a detail rather than just the prescription. Browne has also noticed that more and more Massachusetts builders arrive at that table with Phius Certified Builder credentials already. They understand the intent behind the details. The team then uses their experience on previous buildings to collaborate and to dream up new ways of meeting the intent.

“When you get people thinking that way,” he says, “you end up with a better product for less cost.”

Windows Without Worry

Sourcing high-performance components has become far easier since Apigian’s experience with Distillery North, in part because the market has seen a surge in suppliers. Windows in particular used to cause significant consternation among teams designing high-performance buildings because options were limited and because mistakes could be very costly. In the past, lead times were also exceptionally long. Apigian remembers previous projects where a window supplier's follow-through gave the team real headaches. “They take a really long time, and you have to review the shop drawings months and months before they arrive,” she says.

For Leefort Terrace, the team ultimately decided on INTUS Windows for several reasons. Reliability and customer service were at the top of the list for Apigian. She has confidence that they will deliver on time and show up when challenges arise. They also wanted to use polymer (uPVC) windows to reduce costs without sacrificing performance and went with Supera CW, which are tilt-turn units with a U-value of 0.15.

From a design perspective, the most interesting decision was how the windows went into the wall. Apigian’s preference is to set a window in the rough opening with the frame flush with the outside face of the sheathing, then wrap the air barrier tightly around it, followed by the exterior insulation and the rainscreen. “That’s how I like it,” she says.

Callahan Construction Managers, the general contractor, preferred flanged windows. Apigian agreed on one condition: the flange had to be integral to the frame, not added on, so the connection stayed airtight. The cost of that choice is largely aesthetic. While there can be a modest performance impact, a flanged unit sits farther out in the wall assembly, which leaves a shallower reveal and less shadow line on the façade. “You can do it well either way,” she says.

When asked if he remembers any problems with the windows, Browne responds with a shrug and a laugh. “When someone’s using INTUS, it’s like an afterthought from there,” he says. “I’m like, ‘Oh, good. Let’s talk about other things.’”

Keep It Simple Salem

“A simple, almost code-built envelope can be Passive House when you make it airtight and when you deal with thermal bridges,” Browne says. Leefort Terrace is proof. The building consists of a Type I concrete-and-steel podium beneath three Type V wood-framed residential floors. The assemblies are 2x6 framing filled with wood-fiber insulation from TimberHP, then sheathing, the air barrier, two inches of continuous rigid insulation, and pressure-treated furring for the rainscreen. The team had hoped to use TimberHP's new board insulation for the exterior layer, but it wasn't available in time, so they used the lowest-GWP rigid product they could get. The average R-value for the wall is 28 (see Figure 1 for details). The roof is also a standard assembly (see Figure 2) and has an R-value of 48.

The challenges the team encountered ultimately had less to do with hitting performance metrics and more to do with resiliency measures, as the building is very close to the water. The ground floor is open parking plus a lobby and community spaces designed to get wet someday and dry out without growing mold, with the homes elevated above the 2070 flood projections. The usual way to insulate a podium is to wrap its underside, fighting around steel beams and concrete from below. At Leefort Terrace, the team put all of the podium's insulation on top of the concrete deck, beneath the flooring of the first residential level. Browne knows of only one other project that has done it. “It’s hard to do it underneath,” he says. “It’s relatively easy to do it on top.”

Proximity to the coast shaped the mechanical systems as well. The team studied ground-source heat pumps, but they ultimately dropped the idea because groundwater chemistry near the shore raises the corrosion risk. Instead, the all-electric building uses Mitsubishi VRF for heating and cooling, a central Trane ERV for ventilation, and a rooftop bank of Sanden heat pump water heaters that use CO2 as the refrigerant. From the roof, Browne says, the water heaters look like a row of ordinary condensing units, and the system stages as many of them as the load needs. The footprint for the heat pump water heaters is small enough that the team managed to fit a 146.3-kW PV-array on the roof.

In principle, Passive House is not complicated, and on this point Apigian and Browne, interviewed separately, said nearly the same thing. “Passive House is actually quite simple,” Apigian says. “Seal the box. Then you have to get the ventilation in.”

Heating and cooling are also quite simple. “No one's having a hard time with that,” Apigian says.

Ventilation is another matter. Distribution, testing, and balancing all present problems that are still being debated (see "The Damper Divide” below), though the debate centers less on whether a system can keep a Passive House ventilated than on how much margin for error teams should accept in their design.

These are the kinds of disagreements that arise once the big-picture questions are settled, and this is a point Apigian returns to. Asked what she'd tell a team starting its first large Passive House project, Apigian doesn't talk about windows, podiums, or damper settings. She remembers the early days, when every detail felt like a totally unique situation, and she recommends a more principled approach centered on one question: What sits inside the envelope and what sits outside it? The job is drawing the line that separates the inside from the outside, first around a rectangle on a site plan, then through a wall section, and eventually through smaller and smaller details until you’re dealing with single window jambs.

“It's continuity,” she says. “It's still continuity. It's just at a different scale. It's just, how are you continuing the line?”

The Damper Divide

A constant airflow regulator (CAR) is a passive plastic valve that sits in a duct and adjusts itself as pressure changes throughout the year so that each register delivers the flow it's set for. In theory, that means the system doesn't need constant rebalancing. Aldes, now on the third generation of the product, rates the CAR3 at plus or minus 10% of its setting.

How far to trust those devices, and how much margin to build in above the required minimum, is an active debate among the engineers, CPHCs, and verifiers who design and test these systems. Leefort went through a version of this debate. The engineer on the project, Galen Staengl, founder and principal of Staengl Engineering, started with CAR dampers in his design. Browne argued against them and they were removed. Physical constraints in the design brought them back.

Browne’s concern is a matter of compounding error rates. There is some margin for error in measuring airflow rates (cubic feet per minute [cfm]), perhaps 10% even when done well. A system set to operate at 20 cfm will still be considered acceptable if a verifier measures a rate of 22 cfm or 18 cfm. Both figures fall within that 10% range. CARs add another 10% in variation. If the design flow is set at exactly the ASHRAE minimum, say 20 cfm, a verifier's measurement could land anywhere from 16 to 24 cfm and  a significant number of measurements will show that the project failed to meet the ASHRAE minimum requirement.  Adjusting a system that has multiple failures due to these margins of error in the damper flow rates and the measurement tools can take a lot of time when the building is otherwise ready for occupancy! It can result in the system being forced to operate at a much higher static pressure in order to try to achieve the minimum verified flow rates everywhere—and this can waste energy which the final Phius model needs to include based on the verifier’s final power consumption measurements of the balanced ventilation equipment.

This is not a minor issue, particularly in very airtight buildings. Ventilation rates have to hit a certain threshold to adequately reduce the risk of moisture and health issues within a specific space. Of course, moving the air and providing ventilation requires more energy and potentially larger equipment. This creates some tension between those who want more margin built in and those who want to keep fan energy and equipment size down. Ultimately, the goal is to reach a compromise that balances the two priorities, and this is what happened at Leefort Terrace. Because a CAR's setpoint can be dialed up, the balancers used the settings as an adjustment knob and measured with the same instruments RDH used, which removed one source of disagreement. Where a register came in short, they raised the setting, from 20 cfm to 25 or 30, until the measured flow met the target.

That kind of fine-tuning doesn't happen on every project, so Browne's question stands. That ambiguity cuts against the whole point of verification. “Do you want us verifying so that we can say conclusively we met the minimum requirement,” he asks, “or verifying in a way so we say that we might have—we really can’t tell?” The solution to streamlined final verification is to design a buffer which meets and slightly exceed the compounded error of the balancing process and the verification measurement. “We recommend using 25 cfm for the design value when you need 20 cfm at a minimum, and 30 cfm as the design value when you need 25 cfm,” Browne says.