Largest Passive House Retrofit in Canada
Updated: Sep 10, 2020
By Penny Beaudry
This landmark hotel, banquet hall, and rooming house complex was originally built in the 1960’s. It has now been converted to 57 affordable apartments, with ground floor commercial space for a convenience store, pharmacy, and restaurant. The entire building has a GFA of 45,000 ft² - making it currently the largest passive house retrofit in Canada.
The first building on the site was a late 1800s farmhouse, which later evolved into a rural crossroads rooming house in the early days of automobile transportation. A three-storey addition was built in the 1960s, followed by larger extensions in the ‘70s and ‘80s as George & Mary’s Tavern and Banquet Hall boomed. Fires in the ‘90s and a general decline in the business led to the property being sold to Indwell in 2016.
Indwell's intention was to renovate and create much-needed affordable apartments. Invizij Architects developed a plan that involved demolishing 40% of the building that was structurally unsound due to fires, keeping the largest existing portion with its open-web steel joists and load-bearing exterior walls. The demolished area was reconstructed with steel stud and precast concrete floors on the same footprint, but aligned floor heights for barrier-free accessibility.
Meet the Team
Emma Cubitt is an award-winning Hamilton-based architect and Associate at Invizij Architects. Her passions are affordable housing and sustainability, which helped guide this project’s trajectory. Graham Cubitt is the Director of Projects and Development at Indwell, a Hamilton-based charity that has recently developed over 400 units of affordable housing with supports for individuals seeking health, wellness & belonging in southern Ontario. The teams responsible for the project have since worked on several more passive house projects together. Graham kindly gave an informative tour of the building on August 1st 2018, describing the project and the learning curve it took to make it happen.
Architect: Invizij Architects
Mechanical/Electrical Engineer: CK Engineering
PH Consultant: Peel Passive House
Structural Engineer: Kalos Engineering
Construction Manager: Schilthuis Construction
Airtightness Contractor: Fourth Pig Green & Natural Construction
Airtightness Testing: WSP
During project’s planning phase, the development team was just learning about the Passive House design standards. Indwell committed to pursuing the EnerPHit standard for the project, and Invizij marshaled an experienced team of designers and constructors who were all willing to approach the steep learning curve together. Potential challenges they foresaw included sizing the HVAC system appropriately, achieving air-tightness targets on a complex building envelope retrofit, and ensuring adequate insulation rates given the tight site setbacks of the existing building. In the end, the team’s commitment to working through problems together allowed them to resolve all the constructability issues; indeed, the first blower door test was amazingly low at 0.30 and the final test achieved 0.31 ACH @ 50Pa - 30% of what was allowed by EnerPHit standards! The team's take-away learning was that with good detailing, it is not too challenging to meet PH air-tightness targets with a larger building.
This was the first project Schilthuis Construction had worked on that attempted such ambitious air tightness, so they worked with Fourth Pig Green & Natural Construction to ensure close attention was paid to the building envelope’s construction. That attention to detail paid off, with the building achieving an impressive 0.31 ACH on final testing, while the EnerPHit standard requires 1.0ACH @ 50Pa.
Given the multiple existing wall types, the team determined to wrap the entire envelope with Blueskin air/vapor barrier, use Cascadia fiberglass clips to support the cladding, then apply polyurethane insulation in three lifts creating an effective R-value of +R36. Spray foam was specified due to its high u-value/inch, allowing the exterior insulation approach while not encroaching on the tight property lines. The team decided to use a new spray foam on the market called Insulthane Extreme by Elastochem. Made locally in Brantford, it has a global warming potential of 1 (same as CO2), whereas other spray foam blower agents can have global warming potentials of 1000+. This was important to Indwell as it sought to minimize the environmental impacts of the project.