How Toronto Community Housing Decided on a Passive House Standard for Their Latest Project
PHI vs PHIUS is an ongoing debate in the world of Passive House, with some builders, architects and engineers stringently aligned with one or the other. There is Passive House International (PHI) the original German standard, and Passive House Institute US (PHIUS), the American standard birthed to better adapt PHI to North American climate zones, grid systems and plug loads, as well as various other considerations. But without applied knowledge of both certifications, it can be really difficult to know which standard is better suited for a given team or project and that’s exactly the predicament Toronto Community Housing (TCHC) found themselves in with the development of their Passive House pilot project at Alexandra Park.
Toronto Community Housing (TCHC) wanted to better understand the Passive House approach at the Alexandra Park Revitalization in partnership with Tridel. In the search for a Passive House design team, TCHC wrote a RFP that required the integrated teams bidding on the project to report on the major differences between PHI and PHIUS, and make a formal recommendation on which system they thought would be a better fit for the project. After conducting a comparative analysis based on criteria developed with TCHC, the design team made a recommendation to proceed with the PHIUS path to certification.
Michael Lam, the TCHC Senior Construction Manager on the team that issued the RFP, finds the differences between the two standards quite interesting. “ We are spending public money and need to make sure that we aren’t doing it foolishly. Hinging our decision on individual tastes and preferences isn’t good enough, so we needed to determine which of the differences between the systems would suit TCHC’s needs better.” According to Lam, a major factor in their decision was determined by issues of public procurement. “PHI insists on equipment and materials certified by their standard. Unlike a private condominium development, a public housing project in Canada can’t just specify unusual assemblies or equipment from Europe . Local servicing and repair are critical aspects too. A lot of our tenants are vulnerable, and we need to be mindful of timelines for repair when things break down.”
A rendering of an earlier phase of the Alexandra Park Revitalization. Image Courtesy of TCHC.
PHIUS presented itself as the better alternative for Alexandra Park, not only because of its more liberal attitudes to employable materials and equipment, but also because of its additional site reviews and quality control precautions. “You could potentially look at those things as a con rather than a pro,” says Lam. “You can say it can slow down the project or that these check-ins are too rigid, but we are very mindful of the fact that none of us at TCHC or Tridel have any Passive House experience and the intermittent reviews that come with PHIUS allow us to stay on track and maintain alignment with our deliverables. They are also great opportunities for those of us who don’t know, to learn.”
And of course, the climate adjusted attributes of PHIUS were also important to TCHC. Toronto has really hot, humid summers and really cold winters and working within a framework that takes the local climate into account to guide the design to a cost-effective design was vital. Stuart Evans, the mechanical engineer for the project notes that the climate-specific targets in PHIUS can result in less insulation being required to hit the standard’s energy threshold compared to PHI, and that might prove to be a financial incentive as well. Stuart also observed that while less insulation may be required, the PHIUS air tightness target is harder to achieve on a large building.
Coming to a decision was not easy for the team and it was definitely an issue that came with much debate, but Lam is glad they finally came to a decision and that steady progress is being made on the project, which is set to begin construction in early 2022. “As a social housing provider, it is very unusual to be on the cutting edge of anything, but we really had to ask ourselves, what does a TCHC building look like in 2020?” says Lam. “Passive House is an unquestionable excellent and ambitious standard and although we will build to PHIUS, ultimately, we might not get certified at all. As a housing provider for vulnerable communities, certification is secondary to us. Our main concern is making the best building possible. A building that lasts for fifty to a hundred years. Right now, with our research, that ideal building seems to be in line with Passive House principles, whether PHI or PHIUS.”
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