Record air tightness reached in larger-scale affordable housing projects

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By Peter Vander Klippe, Kasia Bednarz and Josie Costantini

Special to Ontario Construction News

In the midst of this COVID-19 pandemic, two affordable housing projects in Hamilton have set new records for air tightness in larger scale Canadian buildings. Indwell’s 45-unit, 60,000 sq. ft. project in conjunction with Hughson Street Baptist Church, and 50-unit, 35,000 sq. ft.project with the Hamilton Public Library both achieved 0.12 ACH50 in mid-construction testing – that’s 80 per cent less than their allowable limit.

This bodes well for achieving Passive House certification once completed.

We know that high-performance low-energy buildings are needed to meet current and future sustainability goals. With building operations accounting for up to 40 per cent of energy consumption, a key challenge has been finding design standards that actually address consumption and emissions.

Passive House is an internationally recognized approach to designing buildings that need minimal energy to operate, thereby locking in permanent emission reductions. Five key features root this approach: 1) superior insulation, 2) minimizing thermal bridging, 3) high efficiency windows, 4) strict airtightness, and 5) energy recovery ventilation systems. While some elements have technological solutions, air tightness is achieved by skilled tradespeople.

The construction industry has a reputation for sticking with the familiar, so it takes a mindset shift to change how buildings go together. When Indwell pulled together a team in 2016 to rethink our development approach, our architects, engineers, and contractors agreed to never say, “That’s not how it’s done,” but instead remain open to rethinking buildings from the ground up. This commitment has resulted in a high level of comfort on our team with achieving a high level of air tightness through attention to detail during construction.

The air barrier is imagined as a continuous line drawn from under the foundation right around the full building envelope, blocking uncontrolled air leakage. As each trade completes their work – foundations, framers, or window installers – the air-tightness membrane materials may change but the barrier remains continuous.

For Hughson Street Baptist, Henry’s Blueskin products envelop most of the building. At McQuesten Lofts, the Huber ZIP System with liquid flashing is the major component of the air barrier. Both buildings use Soprema’s roofing membranes and W.R. Meadow’s under slab products.

Fear is a powerful driver for many human decisions, and in the case of low energy/green house gas -emitting construction, it is no different. Owners often fear that these buildings will cost significantly more, and constructors fear that they will not be able to achieve the testing standards without undue complications or costly delays. Our Passive House projects prove this these fears are unfounded.

These projects used readily available materials and familiar techniques trades already know. We have realized the big difference is in how the project schedule and assembly sequences are managed; the building envelope must be enclosed for the crucial first air-tightness test, so the roofing and windows have to be done earlier than may be typical.

Our experience with Passive House now spans six multi-residential projects, from new construction to adaptive reuse, and wood-frame to concrete and steel. In each case, the budgets have been within a few percentage points of conventional quality construction and within the same overall schedule.

When we committed to rethinking how we built, we too were worried about whether the Passive House standards would be feasible; now we know that the challenge can be embraced. We certainly expected great things from our team and are thrilled at the record air tightness results we have achieved.

Peter Vander Klippe is a construction project manager for Indwell. Kasia Bednarz is an architectural designer with Invizij Architects. Josie Costantini is a passive house consultant with Schilthuis Construction.

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