By Jay Fox

Some of the most compelling stories coming out of the Passive House community don’t end in shiny new buildings. They focus on what happens when advanced building science intersects with historic preservation and when high-performance construction becomes a tool for community impact.

That was the case in Hamilton, Ontario, where the long-dormant Royal Oak Dairy site was reimagined as supportive housing built around Passive House principles. The developer, Indwell, has been committed to building to Passive House standards since 2018, and they currently provide supportive housing to more than 650 households in southern Ontario.

The dairy property was acquired in 2018, and the rehabilitation was performed in three phases. The first phase saw the construction of two new buildings known as Dairy Lofts and Heartwood Apartments that were each built to meet Phius standards. The second phase focused on the adaptive reuse and deep energy retrofit of the building that originally housed the dairy’s stables, which were constructed in 1929 and operational until 1960, when the dairy discontinued horse-drawn deliveries. Now known as Ain-dah-ing (an Ojibwe term meaning “home within our hearts”), the high-performance makeover ultimately created a commercial space and 13 units of supportive housing. A final phase, which will add another new Passive House building to the site known as Acorn Flats,  is currently under construction.

In total, the project will bring more than 120 units of supportive housing to people with disabilities and people who have experienced homelessness. Additionally, Indwell has partnered with Indigenous health care providers, who will have offices based in the restored stables.

To ensure the ambitious project met performance metrics, Indwell relied on two firms from southern Ontario that are extremely familiar with the intricacies of Passive House construction: Schilthuis Construction and Invizij Architects.

Unfortunately, the stables were in rough shape in many sections. “The two brick wythes were pretty sound, but we took whole areas of the wall down because the mortar was kind of dead,” Contractor Phil Schilthuis says. They installed a new slab-on-grade concrete floor and wood truss roof. “The new floor system ties into the building for stability and we installed a new masonry bond beam at the top of the brick wall which was partially covered by trusses.”

“We had to install interior shoring and had to gut the whole building, the exterior walls and then rebuild from the inside out,” Schilthuis adds.

This approach shines a light on the reality of bringing older structures into alignment with modern airtightness and durability expectations: you don’t just upgrade — you rethink. One of the components that allowed this rethinking of the original wall system and to get it to achieve Passive House levels of performance was PROSOCO's R-Guard FastFlash, a liquid-applied flashing membrane.

In addition to being used in conjunction with a Zip sheathing system for the new construction, FastFlash was a crucial part of the successful retrofit of the dairy buildings because it filled joints and seams, sealed around rough openings, and plugged up any additional cracks and penetrations. Beyond its versatility and performance, FastFlash can be applied to most materials without the need of primers and in damp conditions. It can also remain exposed to sun and weather for extended periods of time without degrading.

“For the FastFlash product we found that it was a better performing liquid membrane than some others that we’ve used in the past,” Schilthuis says. “It applied well with a roller or brush and tools and also had good coverage, so you didn’t have to keep going back to apply the membrane to get the thickness that was required.” 

The use of FastFlash was a gamechanger for the two new buildings, allowing the team to achieve airtightness scores of 0.018 CFM50/SF and 0.014 CFM50/SF. For the retrofit of the dairy, the score was a little higher: 0.064 CFM50/SF or 0.95 ACH50 (note: the Passive House Institute’s retrofit standards, EnerPHit, has an airtightness threshold of 1.0 ACH50).

“Having the option to have the product in pails as well as the 20oz caulking tubes also provided different solutions for the different areas that required air detailing. We primarily used these on the window bucks (see photos above), as well as to detail some other tough areas that we had. In the old conversion we also used it behind the new ledger boards that we installed for the new floor systems as some of the membranes had a harder time adhering and getting a good seal on the old brick walls that we were keeping,” Schilthuis says.

Schilthuis also notes that PROSOCO was easy to work with, that they offered a good support system, and that they ultimately established supply chain with Ontario-based supplier Hewson Brothers so Schilthuis could get the materials they needed without issue.

While PROSOCO's products and services helped the construction team meet performance goals, the real winners are the residents who now get to live in a quiet and comfortable home.

Top image of Ain-dah-ing courtesy of Indwell.