Key lessons on modular housing from across Canada

As modular housing becomes more popular across Canada, many developers, municipalities and housing organizations are asking how it be best delivered – and made affordable. With support from the National Housing Strategy’s Demonstrations Initiative, RDH Building Science undertook a study of 3 modular housing projects and has brought forward a variety of findings.

Project scope and expected outcomes

“We hear from clients across Canada now,” says Elyse Henderson, Energy and Sustainability Consultant at RDH Building Science, Inc. “From First Nation communities in British Columbia, an architect working with an affordable housing organization in Montreal, provincial and territorial governments, housing organizations and campuses looking to build both permanent and temporary multi-unit residential housing.”

Elyse is referring to a growing demand for modular housing – essentially, a way of prefabricating housing units in a factory setting, then shipping them and assembling them at the construction site. The uses of modular housing are as varied as the clientele, and the market is just beginning to understand how it might take advantage of modular housing, and what its limits are.

CMHC reaches out

RDH is a consulting firm that provides science-based advice on energy efficiency and design choices for new construction, existing buildings and heritage buildings. Founded in Vancouver in 1997, RDH has since expanded across Canada and into the United States. It has worked on numerous modular housing projects in North America and even around the world.

CMHC recognizes that modular housing could help to address some of the pressures of finding affordable housing, particularly as those pressures can change faster than most large construction projects can respond.

RDH responded to a CMHC call for applications through its Demonstrations Initiative, which is part of the National Housing Strategy announced in 2017. This initiative provides opportunities for housing experts and organizations to showcase innovative housing solutions – for example, through tours, best-practice guides, case studies and videos – with the aim of helping the industry adopt these solutions across Canada.

CMHC awarded funding to RDH to carry out demonstration activities, including a technical bulletin, Modular Construction for Energy Efficient, Affordable Housing in Canada. The bulletin features modular housing projects in 3 diverse Canadian locations, along with lessons learned – both what to do and what to avoid. RDH also hosted a webinar on its findings, led tours of 2 modular housing projects and produced guidance material on modular housing. One tour was co-hosted by Metric Modular, a BC-based construction firm that specializes in modular construction, in one of its developments still in construction. “This allowed people from the industry – architects, designers, consultants – to come to a site and see the process of modules being assembled and put in place,” says Elyse. As construction was completed in weeks, and the finishing touches within a few months, this was a novel experience for the participants. The other tour was co-hosted with BC Housing in one of the provincial agency’s completed affordable housing developments.

Abbotsford, Bella Bella and Iqaluit

On paper, modular housing seems straightforward: in a factory, build units that are small enough to ship by truck or barge, move them to a construction site and assemble them there. Several advantages are clear: mass production at the factory can cut costs if the volume of production is high enough – for example, if many similar projects are rolled out around the same time – while developers and manufacturers may be able to count on more certainty about their costs. Also, better controls can be put in place for construction quality, such as for airtightness. Perhaps more importantly for remote communities, much of the construction expertise need not be located at the construction site.

However, the building still has to get built, and that means having a suitable foundation, common spaces (such as hallways in a multi-unit residence), and interconnections for power, water, ventilation and so on. What’s more, the units have to be joined together: a single dwelling might include several modules and the whole structure must be able to repel water and wind.

Conditions vary greatly across Canada, so RDH looked at 3 early modular housing projects:

• Abbotsford, British Columbia aimed at combatting the city’s homelessness by building a 3-storey, 44-unit modular apartment, to help residents move toward more permanent solutions. The residence has 8 accessible units, a kitchen and common dining area, and rooms for support services. Notably, the building was designed for excellent airtightness and energy efficiency. While Elyse describes the design as fairly standard, she sees this is an advantage: “This is a good example of a replicable design for affordable housing, and became one of several projects across the lower BC mainland with an almost identical design.”
• Though right on the coast of British Columbia, Bella Bella is remote, in that it’s not easily accessible except by boat. After a building fire, local health staff were displaced and housed temporarily in a hotel dedicated to fishing tourism. The aim was to erect the new building and house the health authority staff before the fishing season brought in tourists who could displace the staff from their temporary accommodation. “It was exciting they could meet in tight timeline, despite the fact that this was the first time that this team had used modular housing to achieve a Passive House performance building,” says Elyse. “But, with a clear timeline and set of goals, and an understanding of the review points, along with constant site visits, they made it.” She notes that the project saved considerably on transportation costs by shipping the modules with all the interior furnishings and appliances already inside, reducing the need for a separate shipment.
• In Iqaluit, Nunavut, a 102-room modular hotel aims to meet a local shortage of hotel spaces, while also providing temporary housing to locals. Given the short construction season, modules for the hotel were built in the winter and shipped north and assembled in the summer. A convention centre is also attached to the hotel.

The technical bulletin illustrates some of the many possible uses of modular housing – for example, to house temporary workforces, such as for mines. However, Elyse cautions that modular construction does not necessarily make housing affordable, though it can be a means to provide affordable housing. “Prefabricating can overcome hurdles at the building site, especially with the growth of high-performance construction. Imagine workers trying to install 8 inches of exterior insulation on intermittent cladding supports consistently 5 storeys up. Getting a continuous air barrier could be challenging, but a prefabrication plant offers a controlled environment, which helps.” If those barriers are part of the expense, then modular housing might make it more affordable. She adds that RDH is now studying which factors – such as the characteristics of the design, the costs of labour and materials, and the location of the site – make modular housing affordable. “In the far north or remote communities, where both materials and labour are less available, modular construction can make affordable housing quite a bit cheaper, but it’s not the same across Canada.”

Lessons learned

The case studies – along with consultations by RDH with experts in some other areas, such as permitting, housing management, manufacturing and delivery – brought out a variety of lessons, detailed in the technical bulletin. Construction timelines hold the most obvious advantages, as the foundation is usually built while the modules are still in the factory or being shipped, and much of the building envelope can be assembled in the factory as well. Modules can be craned into place and assembled as soon as the foundation is ready.

Other aspects of delivering modular housing might not be evident to a developer, however. For example:

• The speedy construction pace is also less disruptive to the community. Conversely, development permits and rezoning do not necessarily speed up for a faster build.
• Transportation is severely limited – primarily by the width of roads, a serious consideration when dealing with remote communities. However, the manufacturers also have to take into account that the modules have to be able to withstand the conditions of transport, particularly moisture from roads, weather, and bodies of water. Elyse says that “There’s a gap in standards between manufacturing facility and the site. So, the design team has to come up with a transportation method that includes moisture management and that’s sometimes been done poorly. RDH has been called in for forensic investigations and found mold growth in some modules and completed buildings that has required costly remediation.” This isn’t unique to modular construction, as the materials used are the same as for site-built buildings. However, modular buildings are unique in that the level of finish provided within modules is sensitive to moisture before the roof and walls are sealed up.
• In some ways, site selection can be easier than for conventional construction, because the modular designs for affordable housing buildings might not need as much below-grade preparation (though this is not the case if the design includes below grade parking). However, there must be space above for a crane to move the modules into place, as well as space to store the modules during assembly.

Scaling up across Canada – with caution

It’s clear that modular construction could be scaled up across Canada as a way to build more affordable housing. The Government of Canada recognized the advantages of rapidly building modular housing when it launched the Rapid Housing Initiative in 2020 to address urgent housing needs brought on by the COVID-19 pandemic.

However, Elyse cautions that modular construction is no silver bullet. For example, “Northern communities can take advantage of available labour and materials down south, but some of them would prefer to train local people, which can have economic benefits. It’s important to listen to the stakeholders involved and take into account what these communities actually want.”

Similarly, she stresses that the main driver of success is consultation. “Bring all the members of the team together at the beginning, and make sure that everyone is clear on the goals, the timelines and their responsibilities. That’s because, once you start manufacturing the modules, there’s no going back.” She says that this consultation was instrumental to the success to the community and parties involved with the Bella Bella project.

She also encourages developers to think of the end-goals of the project, including its eventual disassembly, if the building is intended to be temporary. Modular housing cannot always easily be reused for all purposes, such as a home for temporary workers becoming a shelter for homelessness, which had different privacy and security requirements.

No doubt, many developers will look to RDH’s findings with interest and to learn more as the company studies some of the factors that make modular construction a viable option for affordable housing. RDH expects to continue this work, along with a “deeper dive” into cost analysis and the effect of modular construction on developers’ ability to obtain financing from lenders. RDH is also partnering with BC Housing to create a tool to help teams decide whether to use modular housing for their affordable housing projects.