In its original request for proposals document, BC Housing specified that Vienna House would incorporate offsite prefabrication strategies to increase quality control, reduce on-site construction time, and reduce waste and environmental impact.
In practice, that could mean any range of potential solutions—from complete prefabricated buildings, to panels built offsite to precise tolerances, trucked to the site and flown into place via crane. The Vienna House design team is currently working to identify the approach, or combination of approaches, that will make the most sense.
At a recent meeting of the Vienna House Technical Research Committee, representatives from the offsite, prefab, modular, and panelized construction sector outlined various solutions, strategies, and resources. Here, we offer a quick recap.
Paradigm Panels uses automated fabrication and standardization in a bid to reduce the costs of high-performance construction.
In November 2020, the company fired up the saws at its new cutting-edge factory in Barrière, British Columbia. The facility produces high-performance open and closed-wall panels using construction automation equipment developed in Sweden by Randek.
The plant uses LEAN manufacturing principles; for example, the team colour-codes raw materials and components for efficiency. The plant can produce up to 160 feet per hour of sheathed materials, including a two-by-10 wall with an R39 effective insulation value.
The video below shows how one assembly line robot at the plant picks up a piece of sheathing, squares it up on the frame, and then another moves in and nails it, with exactly the right pressure, in a perfect pattern. “On a 20 foot wall, they are only off by one millimeter,” said CEO Stefan Maunz. (The team nicknamed the two robots “Hans” and “Frans.”)
Once insulated and taped, the panels meet and exceed the air tightness requirements for Step 5, Part 9 of the BC Energy Step Code, and are suitable for builders targeting the Passive House standard, Maunz said.
BlackBox Offsite Solutions
Craig Mitchell of BlackBox Offsite Solutions, a consulting firm, outlined the recipe for success when approaching an offsite, prefab, modular, or panelized project.
“Collaboration with all partners is mandatory,” he said. “This means the consultants are sitting around the table with the general contractor, the trades, the modular or offsite builder, and in many cases the owner.”
Mitchell called offsite construction a “team sport.” High performance buildings, including those targeting the passive house standard, require a lot of up-front collaboration to ensure all the details are right, and that the energy modelling will meet the desired certification standard. Vienna House is using this same integrated design process.
“It becomes extremely costly to make changes in construction while it’s in production,” Mitchell said.
(A company he once worked for calculated the cost of changes while in production at $17,000 per hour; that’s the cost of slowing the production line while awaiting a decision, he said.)
Mitchell stressed the importance of understanding a project’s drivers, such as quality, speed of delivery, location challenges, revenue generation, or environmental attributes. Not every building should be built offsite, he added. “Are there repeatable elements? Is there a layout consistency? And are there large portions of the project that can be built using off site techniques. There are also constraints that need to be taken into account.”
“Finally, what is the culture of the team? Do any of the players have a track record in offsite methods? If not, then is there the willingness to learn?”
Mitchell concluded with seven considerations for making better use modular and offsite construction:
- Think differently about the construction process, and breaking down traditional barriers to execution.
- Modular and offsite builders are not created equally. Prequalify and engage candidates early.
- Early planning and detailing will result in a well executed project which will breed success. The more detailed the design, the better.
- Collaboration is key to offsite success, which will lead in turn to higher adoption.
- Offsite must be seen as a system, with a push toward standardization.
- Standardization will lead to scaling and faster delivery—especially in affordable housing and seniors housing.
- High performance housing is better delivered in an offsite manner.
FPInnovations is a not-for-profit, private, applied research centre that supports the Canadian forest sector’s global competitiveness.
Dorian Tung, the organization’s manager of building systems, presented to the Vienna House technical committee on his organization’s testing and building science research work.
The FPInnovations team outlined how its advanced research and evaluation facilities are testing various types of wall systems and assemblies, with separate “testing huts” measuring performance of light wood frame walls, mass timber and cross-laminated timber, and five types of prefabricated panels. Sensors embedded in the walls measure envelope performance and indoor environmental conditions such as temperature and CO2, relative humidity, water and airtightness, moisture content, and energy consumption needed for space heating.
A new testing hut, under construction, will look at the performance of panel and sheathing connections, and airtightness performance.
Timber Engineering Inc.
Robert Malczyk, principal of Timber Engineering, presented an economical mass timber / steel hybrid structural solution suitable for seven- to 12-storey buildings, which are too high for light wood framing and suitable in situations where concrete is expensive. The system is a hybrid of cold formed steel (steel studs) for load bearing walls, with floor slabs made of cross laminated timber.
Malczyk made the case that the hybrid system is faster, significantly cheaper, and offers site efficiencies. The wood ceilings also offer strong design benefits. “A lot of clients want to have exposed cross-laminated ceilings,” he said.
Timber Engineering is currently implementing the approach on an 11 storey building at Main and Cordova streets in Downtown Vancouver.