Greenbrae Apartments: Affordable and Passive House

Repurposing the Commons in Lake Oswego

Greenbrae Apartments at Marylhurst Commons did not begin as a Passive House project. A partnership between the Sisters of the Holy Names of Jesus and Mary and Mercy Housing Northwest, the 100-unit and 100% affordable apartment building in Lake Oswego, Oregon, was always intended to be high-performance, but the decision to pursue Phius certification occurred only after design development had started. The unorthodox move may have caused some sleepless nights for the team, but it did not prevent them from passing their final blower door test.

As rigorous as Passive House standards are when compared to code minimums and as much as the pursuit of certification may seem daunting to those who are not experienced with passive principles and methodologies, the success of this project should be an inspiration. It highlights that a team with a strong foundation in high-performance building and willing partners can overcome the challenges associated with changing course midstream. Once it receives its final certification, Greenbrae will be one of the largest Passive House projects on the West Coast.

The Sisters and Marylhurst

Greenbrae Apartments are located on the former site of Marylhurst University. A steady decline in enrollment that started in the late 2000s led the university to close in 2018, and ownership of the 4.3-acre campus reverted back to the school’s original founders, the Sisters of the Holy Names of Jesus and Mary, who have owned that property and the surrounding area since 1906. In total, the religious organization’s holdings in their corner of Lake Oswego amount to 63 acres.

The property surrounding the university did not remain undeveloped over those years. The Sisters have created a thriving community that encapsulates their mission of education, social justice, and the empowerment of disenfranchised people. They have built educational residences and offices for members of the religious organization, as well as an expansive retirement community (Mary’s Woods), several schools, and a Franciscan prayer center. Creating deeply affordable housing seemed like a natural progression on the former site of two of the university’s student residences and a common building, given the Sisters’ commitment to serving marginalized communities and the Portland metropolitan area’s dire need for more affordable housing. As the three buildings were beyond repair and could not be salvaged, the Sisters decided to demolish them and erect a new one in their place.

For help with the development, the Sisters turned to Mercy Housing, with whom they entered into a ground lease in 2022. Originally founded by six communities of Catholic sisters in the early 1980s, Mercy currently develops, manages, and owns affordable housing complexes across 41 states. Mercy Housing Management Group, its property management division, is responsible for over 300 properties and more than 22,000 units. Its northwest division, Mercy Housing Northwest, owns and operates 52 properties across Idaho, Washington, and Oregon.

Despite its footprint in the region, Mercy was not familiar with the affordable housing landscape in Portland and did not have a project architect in mind as they began to build their team. For assistance, they reached out to Walsh Construction Co. with whom they have have worked together on at least a dozen affordable projects, the majority in the Seattle/Tacoma region, and have a strong and established relationship.

Walsh directed them to Carleton Hart Architecture (CHA), a certified B Corporation and Just label firm based in Portland with a similar commitment to social justice as the Sisters and Mercy.

Rethinking What Affordable Can Mean

“We were part of a young industry that was trying to change the way we think about affordable housing,” Carleton Hart Architecture Principal Brian Carleton says of the firm’s early years. Even before the Great Recession, CHA recognized that affordable multifamily housing could be sustainable, efficient, innovative, and even beautiful, defying the prevailing wisdom at the time, which was that the typology needed to be utilitarian.

“These projects are important parts of our community,” Carleton says. “They really add to and diversify neighborhoods, so it’s important that they’re built right.”

The city government and the people of Lake Oswego agreed with this assessment, as well as CHA’s design, and approved the project at the end of 2020. While CHA’s philosophy helped to warm the suburban community to the promise of affordable housing, Carleton personally credits CHA Project Manager Melissa Soots, who presented the team’s vision during design review, for the success. “They came to an understanding that they really do need more affordable housing in the city—and, with the right team, that it can be done well,” Carleton says.

Carleton acknowledges that even with supportive communities and development teams, there have been limitations to what can be built. “I think our effort in sustainability and innovation always comes with a healthy dose of concern for what’s feasible—what we can really do with the dollars at hand,” he says. Consequently, they had regularly been able to pursue certification through Earth Advantage (an independent, third-party verifier of green buildings based in Oregon), but had yet to attempt Passive House certification.

However, the question of doing a passive project had long seemed less like an “if” and more like a “when” for the firm, as several individuals at CHA are certified Passive House professionals. It was no surprise that the topic came up repeatedly during pre-design with Greenbrae. Even when Walsh officially signed on during the concept design phase in May 2020, it continued to seem like a possibility.

“We are always asking how we can push our sustainability goals beyond code in a way that promotes health and wellness,” Mercy Housing Northwest Vice President of Real Estate Development Colin Morgan-Cross explains. “At the end of the day, families deserve a comfortable, safe, and healthy place to raise their children.” 

Morgan-Cross adds that the improved indoor air quality, thermal comfort, and noise control in Passive House buildings have been some of the primary motivators in Mercy’s interest in the standard. Optimizing performance and providing tenants with a healthy and comfortable home shouldn’t be an either/or decision, Morgan-Cross observes, though the upfront costs to do so can push budgets beyond their limits.

“We knew that Mercy Housing had strong sustainability goals and Walsh has experience with Phius,” Soots adds. “The Sisters of the Holy Names really wanted to push sustainability, as well.”

Unfortunately, as the project progressed, it seemed more and more like Phius certification was simply beyond budget limitations. Once the team entered into design development, CHA and Walsh assumed that the matter was settled.

Rethinking Passive House

According to Morgan-Cross, the Sisters have always seen themselves as the long-term stewards of the land, and they take both resiliency and durability very seriously. “They’re thinking about what this property will be like in 200 years,” he says.

As a result, they decided to make a significant philanthropic contribution to the project that largely covered the upfront costs of Phius certification. Additional funding sources came from Oregon Housing and Community Services, Metro, and the Clackamas County Housing Authority.

The decision occurred about a month into design development. The design team was excited, of course, but they also knew that this would require rethinking many of the building’s details.

The good news was that there were several factors working in their favor. First and foremost was Walsh’s experience with the nuances of Passive House construction and the process of certification. “I think the greatest benefit that Walsh brought to the table was just the confidence of having done it before,” Carleton says. “It is really, really helpful to have at least one member of the team who has gone through it,” he emphasizes.

This confidence translated into clear performance and cost comparisons that helped CHA determine if certain aspects of its original designs could remain in place or if they needed modification. Walsh Quality Director Sharon Libby Eyerly notes that CHA has a “collaborative spirit”, and that their willingness to work together made the process a lot easier.

Eyerly and her department are experts in collaboration and sharing information, and they have been instrumental in making sure that the lessons learned by Walsh as a company are shared out to their field crews. “Since our quality department and our quality managers touch every project, we have a really great way of disseminating that information and recycling what we learned back into the next project,” she says.

Beyond their collaborative spirit, CHA had already adopted many passive building techniques as part of their standard practice even before they began working on Greenbrae. As one example, they have long relied on building orientation to optimize solar gains in the winter and use existing trees and passive shading elements to limit these gains in the summer. Another example clearly illustrated by Greenbrae’s massing is the firm’s use of simplified form factors. The four-story, U-shaped building is accented by a pair of setbacks on the fourth floor, which are each only about 2,500 square feet. The design decision may have been unintentional from the perspective of achieving Passive House performance when it occurred during schematic design, but it turned out to be serendipitous once the team decided to pursue Phius certification. According to Soots, Walsh’s coaching was most helpful for the team as they figured out how to detail the enhanced air sealing techniques necessary for Passive House, resulting in some unique assemblies.

Collaborating on Campus

The design became significantly more complicated following the decision to pursue Phius certification, but the team managed to weave the continuous air barrier through the various assemblies, as shown in the details. According to Nate Latigue, a job captain for CHA, the assembly of the sloped portion of the roof contains an air and vapor barrier sandwiched between the roof deck and a Hunter panel system, which provides rigid roof insulation. Specifically, the Hunter Panels product used is the Cool-Vent, which is a vented nailbase product that provides ventilation under the secondary layer of plywood and asphalt shingle roofing. The portion of the roof that is flat consists of plywood, the air and vapor barrier, polyisocyanurate rigid insulation, cover board, and then thermoplastic polyolefin (TPO) on top of that.

Throughout construction, air sealing continued to be one of the more intimidating and nerve-racking aspects of shooting for Passive House certification. However, the team from CHA felt that Walsh’s confidence both during design and on the jobsite helped to calm their anxieties. As Carleton says, “It’s wonderful having your site superintendent just say, ‘If we do it this way, we’re going to pass those tests. Do not worry about it.’”

Another element of the building that proved daunting was the installation of the all-electric domestic hot water system. Even before deciding to strive for Phius certification, one of the initial sustainability requirements for the Sisters and Mercy was that the building be all-electric, and the team accepted the challenge. As a result, Greenbrae is one of the first multifamily buildings in North America to be equipped with Mitsubishi’s domestic hot water heat pump system.

Meanwhile, heating, cooling, humidity control, and ventilation for the building are provided by a centralized dedicated outdoor air system (DOAS). The normal settings for the system will be able to keep occupants comfortable for the vast majority of the year, especially given the mild climate of the Portland area and the building’s well-insulated envelope. For excessively hot days, the team worked with ColeBreit Engineering, the mechanical and plumbing engineers on the project, to devise a way to add more cooling capacity to the HVAC system. The energy recovery units have heat pump coils that utilize refrigerant to cool (and heat) the air further to provide ventilation air at a tempered, comfortable temperature to the apartment units and common areas. 

Maintaining a steady temperature in the shared laundry room is also a concern, as it sits within the Passive House envelope. To prevent overheating in summer or overcooling in winter, the makeup air louver actuator has been designed to respond to dryer operation. Soots notes that the space is cozy and that the best place for the actuator turned out to be nestled beneath the window. Rather than sacrifice this space to the mechanical system, the team instead created a small window seat in this space with a vent beneath it. As a result, residents can enjoy the view of the former Marylhurst campus as they wait for their laundry.

Rethinking What Community Can Mean

Construction on Greenbrae was completed in spring of 2024. As noted earlier, the project passed its final blower door test with a score of 0.049 cfm/sf @75Pa (0.041 cfm/sf @50Pa), recently received designed certification, and can most certainly be deemed a success by any standard.

It’s also a success for Lake Oswego.

The city is not known for building a lot of affordable housing. Like many suburban communities, it has long eschewed multifamily housing of all types, including affordable housing. However, this is changing, and positive experiences with the teams like the one behind Greenbrae will only accelerate the push to build more affordable—and passive—housing in the Pacific Northwest.

“With the right partners, it is possible to do both,” says Morgan-Cross.

(Read complete article by Jay Fox on Passive House Accelerator: Repurposing the Commons in Lake Oswego | Passive House Accelerator)