By Jay Fox

When finished later this year, Vienna House will bring 123 units of affordable housing to Vancouver’s Kensington – Cedar Cottage neighborhood. As its name suggests, one of the things that makes the project unique for Vancouver is that its design and construction were influenced by housing projects from Austria’s capital city. In addition to emulating some of the practices common in that city, Vienna House was also designed to be more prosocial than the typical multifamily building. As the project team learned from extreme weather events that occurred in 2021, encouraging more socialization among residents not only improves quality of life; it can also save lives.

What’s in a Name?

Vienna has become a magnet for Passive House construction, with the number of projects certified by the Passive House Institute within the city ballooning within the last twelve years. The surge in Passive House construction follows the certification of the world’s first Passive House office tower (RHW.2) in 2013, and includes multiple large-scale multifamily projects, including the Eurogate district, which has already created over 800 units of PHI-certified housing through its initial phase, with future phases set to bring more than 1,000 additional units.

On top of building more sustainably, Vienna also stands apart because the city has managed to remain affordable while other cities in Europe and North America have seen rents shoot into the stratosphere. Data from May 2023 found that the monthly rent for a one-bedroom apartment in Vienna was approximately half the cost of a comparable apartment in Berlin and less than 25% of the rent for a similar apartment in New York City. Largely due to the city’s four-pillar approach, which considers social sustainability, architecture, ecology, and economy, while also keeping rent within the range of 20-25% of tenants’ monthly incomes, Vienna has succeeded in taming rent prices.

The same cannot be said for Vancouver. Housing costs have been rising in the city for many years, making Vancouver one of the least affordable cities in Canada. This unfortunate distinction motivated a Vancouver City Councilor to look for international solutions, and they eventually met with representatives from Vienna. Their talks resulted in the signing of a Memorandum of Cooperation in 2018 with the goal of sharing best practices to create innovative, low-carbon, and affordable housing, and several years of collaboration.

These kinds of agreements are relatively common and don’t always lead to major developments, but the partnership between the two cities led to a series of workshops and meetings that ultimately produced two multifamily buildings that each contains more than 100 units of housing: the Vancouver House in Vienna and the Vienna House in Vancouver. In addition to building large-scale affordable housing buildings in each city (which is already an achievement), the two project teams also prioritized broader goals, including:

• Providing occupants with a strong sense of community,

• Making the buildings more resilient to the stresses of climate change,

• Major reductions in operational carbon realized through PHI certification,

• The use of more sustainable materials to reduce embodied carbon,

• Developing methods to accelerate development and construction times.

On account of these priorities, both projects opted to utilize prefabricated, mass-timber components. However, given space constraints, this article will focus solely on how these priorities were realized during the design and construction of Vienna House.

The goal of community cohesion is typically presented as a quality-of-life issue, even if there is no clear metric to measure it and its benefits are often difficult to quantify. Being on friendly terms with one’s neighbors just seems intuitively desirable, especially if it means that neighbors are socializing together and feel as though they can rely on one another in times of need for mutual aid.

When the design phase began in spring 2021, the design team, which was being led by Vancouver-based Public Architecture + Design, was already committed to creating this kind of atmosphere in the building. However, the team recognized just how vital this kind of community building could be for vulnerable populations in the early summer of 2021.

Between June 25 and July 1, an atmospheric phenomenon known as a heat dome caused temperatures across B.C., Washington, and Oregon to skyrocket, and they remained consistently 20°C or 30°F above their seasonal average for the entire week. The unrelenting intensity of the heat is believed to have directly caused 619 deaths across the province, making it the deadliest weather event in Canadian history.

As is so often the case with fatalities due to extreme heat, seniors were disproportionately impacted. However, there were two additional factors that exacerbated the tragedy. First, many individuals in the Pacific Northwest, especially in B.C., did not have active cooling systems. Historically, they have not needed them and even many buildings that have been constructed within the last decade do not come equipped with the kinds of air conditioning systems that are commonplace in other parts of North America.

Second, many seniors were still sheltering in place due to COVID-19 restrictions and were living in isolation. It should be noted that isolation among seniors was not a new phenomenon by any means. There is a tremendous amount of literature on isolation among seniors in general, as well as the connection between social isolation and increased mortality rates among seniors during extreme weather events. However, the more intensive isolation due to COVID-19 made matters worse.

According to Public Architecture Founding Partner John Wall, the recognition of just how deadly social isolation can be for vulnerable populations motivated the team to consider social cohesion as a form of resiliency, and so they set their minds to finding novel ways to make the future residents of Vienna House feel like they were part of a larger community. In particular, the team looked into how massing and floor layout can influence socialization and if there is a notable difference in how much neighbors interact when living in a building with typical double-loaded corridors compared to a courtyard scheme.

Through the use of the FLUID Sociability platform, a 3D digital modeling tool that simulates predicted interactions within a given layout, the team was able to determine that the courtyard option was superior with respect to encounters and greetings. (Within this context, an “encounter” is defined as an interaction where a resident sees another person and there is an opportunity for eye contact or vocal acknowledgement. A “greeting” is defined as a slightly more interactive engagement between residents that may involve eye contact, vocal acknowledgement, or a short wave.) According to the software, the likelihood of encounters and greetings in the courtyard model increased by 57% and 35%, respectively.

Wall notes that the software’s predictions matched More Than a Roof’s observations: that properties with courtyards tend to be more social than buildings without them. Given the breakdown of the units in Vienna House—which contains 54% studio and one-bedroom units, compared to 46% “family units” that include two-bedroom, three-bedroom, and even four-bedroom units—the hope is that the intermingling between tenants will create a more cohesive atmosphere, as well as intergenerational relationships between families and senior residents. According to Wall, More Than a Roof intends to further encourage a prosocial environment within the courtyard area or other community spaces by holding numerous events that include social dinners, book clubs, and even resume writing clubs.

Unlike a double-loaded corridor, the courtyard layout will ensure that occupants can always open at least one window without hearing either car or train traffic. Tenants can also open windows on opposite sides of their units to create a cross-breeze and boost ventilation. As the PHI-certified windows and exterior doors are triple-pane Defender 88PH+ PRO by Innotech Windows + Doors, closing the windows means virtually eliminating outdoor noise, including the train. In case of smoke events, the high-performance windows and doors, as well as the airtight wall assemblies and mechanical ventilation, ensure that occupants remain thermally comfortable and are provided with a continuous source of fresh, filtered air.

The design team has made excellent use of passive cooling elements. The fixed shading from walkway overhangs along the courtyard and from balconies on the exterior side of the building have been strategically placed to prevent overheating. Additionally, the southern- and western-facing windows have been outfitted with adjustable exterior solar shades supplied by MHZ North America. Wall notes that they can be mechanically raised or lowered by the occupant.

Given the courtyard layout, which facilitates natural ventilation, as well as the focus on high-performance fenestration and passive shading elements, the design team found that they could dramatically downsize the active cooling system for the building when compared to what they would have needed for a double-corridor building. The reduction in complexity reduced costs, helping to offset the premium associated with building a courtyard. Given these savings, Wall estimates that the premium for the courtyard will be only around 5% of the project’s final costs, though this figure is a bit hazy due to market fluctuations due to the pandemic.

The active cooling system for the building relies on centrally located ERV units manufactured by Oxygen8 that have been outfitted with cooling coils. Wall notes that apartments are not fully air conditioned, as the building was designed to keep the units at a comfortable temperature of around 20°C (68°F) but may occasionally reach 25°C (77°F) when outdoor temperatures are at their absolute highest, which may only happen a few days out of the year. Occupants can rely on mechanical ventilation alone during cooler months, or the system can operate in ‘mixed mode’ which combines natural ventilation with mechanical ventilation when the weather is more temperate. On the hottest days, occupants should close the windows and rely solely on mechanical ventilation. Should any of the more vulnerable or heat-sensitive residents want a cooler room, there will be a fully air-conditioned amenity room on the ground floor.

Heating is provided by all-electric baseboards. The domestic hot water system is also all-electric (the Sanden SANCO2 model, which uses carbon dioxide as a refrigerant), and the water tanks are located in a penthouse on the roof. For a more detailed discussion of the building's mechanical systems, check out the videos below, as well as the episode of the Passive House Podcast with Project Architect and Certified Passive House Designer Jamie Harte of Public.

The interior walls also come to the site prefabricated and are similarly hoisted into place, and then they are installed by workers onsite by Seagate Mass Timber. Unlike many other prefab buildings, the interior walls are loadbearing, which eliminates the need for steel support columns. In fact, even the elevator core is made of CLT, though they do have steel cores for the stairs and walkways due to code. Due to the courtyard layout, neither the elevators nor the stairs are within the Passive House envelope.

The floor structure relies on CLT panels manufactured by Kalesnikoff Mass Timber, which is based in Castlegar, BC. These are also hoisted into place before being secured by workers from Seagate, as well. In terms of sequencing, Seagate installed the interior load bearing walls before the exterior wall panels and then installed the floor above.

Wall notes that the team worked with acoustic consultants to ensure all units are quiet, so on top of each floor panel is a 12-mm acoustic mat, a 38-mm concrete topping, and then vinyl flooring. This is for the living areas, where the CLT panels are exposed in the ceiling. In the bedrooms, there is also a small drop with gypsum board in the ceiling. “The idea there is it helps deal with flanking noise between units,” Wall notes. Though the aesthetics of the unit interiors are shaped by the CLT panels, the cladding system on the building’s exterior is prefinished steel siding, courtyard’s façade is a white, cementitious panels.

Though the building is seven stories in height, it appears to be only six stories from the street. Those six stories are all made from mass timber and light wood framing. The lowest level is made of concrete, including the foundation. Because the site is steeply sloped to one side, about two-thirds of the lowest floor is used for parking, bike storage, and mechanicals. The remaining one-third can accommodate a bank of six apartment units that looks out to the north side of the property and the SkyTrain. As Wall notes, the foundation is a rather conventional slab on grade system with both strip and pad footings and insulation beneath the conditioned space.

Given the different purposes the floor serves, the detailing is a bit more complex, though the foundation has an average USI value of 0.134 (R-value: 42.4). While the residential units are within the Passive House envelope, the mechanical rooms and parking garage are not.

The roof will be outfitted with a PV array, though the exact size is still being determined. Installing onsite batteries to further enhance resilience is currently under consideration at this time. Like the floors throughout the upper levels, the roof is comprised of CLT panel with additional insulation and a membrane on top of that, which has a USI-0.068 clear field value (R-value: 83.5). Wall says that one of the benefits of working with CLT for the roof assembly is that it helped to mitigate thermal bridging. “The nice thing about CLT is you have a nice, simple substrate to anchor things to,” Wall says. “You can screw down into them.”

Occupancy is expected later this year.

Lessons Learned

Without question, Vienna House is a landmark project. By lowering both embodied and operational carbon, while also including onsite renewable energy generation, it is demonstrating how cities can meet even the most ambitious climate goals. Meanwhile, its use of technologies to create a more prosocial environment not only improves individual occupant resilience during times of crisis; it also plants the seed for the creation of a genuine sense of community.

Accomplishing all this was no easy task, and it would not have been possible without a strong and experienced team capable of working collectively. When working at this scale, Wall recommends that the team should include an external and experienced Passive House consultant, Introba. While Project Architect Jamie Harte is a CPHD, it is helpful to have an additional expert on-board dedicated solely to this key project aspect.

While prefabrication helped accelerate the construction timeline, it was also compatible with building information modeling/management (BIM) systems. By using BIM, teams can create data-rich and 3D representations of the building model that can be digitally accessed by team members, including prefabrication manufacturers. Wall has found that BIM helped ensure structural and the mechanical, electrical, and plumbing engineers remain on the same page as the architects. This ultimately helped to reduce conflicts and to optimize coordination. It also gives the trades clear instructions when they are doing their shop drawing work.

“The more coordination you can get, the tighter your structure will be and the fewer conflicts you’ll have on site,” Wall says. This translates into a project that stays on schedule, remains on budget, and meets performance targets.