August 16, 2017

Hooray for Double Standards: Passive House + LEED Platinum in Quebec

  • A view of the beautiful Springhouse, which is both Passive House and LEED Platinum certified. Photo credit: Construction Rocket Inc.

Sarah Cobb and William Murray of Construction Rocket Inc. are dedicated to bringing about radical change in the building industry. As Passive House Certified Builders, they are committed to ensuring energy performance, even in harsh, challenging climates. And their recently completed Springhouse in Abercorn, Quebec, proves that Passive House design and construction doesn’t have to compromise anything: in addition to being Passive House certified, Springhouse has also achieved LEED Platinum certification, and – just for good measure – is also an example of beautiful, compelling architecture.

LEED Platinum and Passive House, Designed in Tandem

When she talks about the performance of a typical home, Sarah uses the metaphor of a parked car idling on a hot summer day: as the car’s occupants sit in the comfort of an air-conditioned interior, the motor pumps more heat (and CO2) into the hot summer air. By going Passive, this waste can be eliminated, or at least dramatically reduced – bringing huge cost savings to occupants while lightening the environmental footprint of buildings.

But for Sarah and Will, even the amazing performance of Passive House wasn’t enough. The choice to seek both Passive House and LEED Platinum certification is reflective of their holistic, sensitive approach to design. Passive House standards do the heavy lifting of reducing building energy loads and cutting back on the emissions associated with space conditioning, but the responsibility of material choice is left to the designer. Taking a holistic approach to occupant and environmental health above and beyond energy performance is a point of focus for 475, and why we take such a strong stand against the use of spray polyurethane foam insulation. So we really identify with Cobb’s decision to pursue LEED Platinum to advance these goals, and to build the absolute best possible standards.

Which isn’t to say that achieving Passive House standards was easy: Abercorn is a pretty punishing climate, with cold, dry winters, and hot, humid summers. It was necessary to design an envelope with the responsiveness and flexibility to deal with wide climatic fluctuations – an ideal task for the Pro Clima system.

Springhouse design specifications: Responsible High-Performance, Intelligently Designed

Springhouse has a double-stud wood wall construction, fitted with 17” of dense-pack cellulose insulation. Cobb and Murray chose vapor-intelligent INTELLO PLUS membrane as the interior air barrier, fitted with a 1.5” service cavity, which will help ensure the longevity of the membrane, behind the drywall. SOLITEX MENTO 1000 serves as the building’s exterior air barrier and WRB, and was fitted with 1.5” fiberboard, double furring strips, and vertical hemlock siding. This wall assembly achieves a total insulation value of R-69. The roof assembly, which consists of raised-heel trusses, includes 27″ of cellulose insulation and hits R-100.

For ventilation, HRV units ensure a constant supply of fresh air, while also drastically reducing the amount of energy needed to condition the interior environment. To further reduce the energy demand, they coupled this HRV with a geothermal loop (250′ glycol line, running seven feet underground) and two mini-split heat pumps to efficiently meet the building’s (low) energy demand.

Cobb and Murray were extraordinarily meticulous in the design of their building, taking many steps to ensure continuous airtightness. Paying particular attention to challenging joints where air sealing can be most difficult to achieve, the architects chose products specifically designed to handle these tough joints and penetrations – such as ROFLEX and KAFLEX gaskets for pipe and wire penetrations, respectively, and EXTOSEAL FINOC for capillary breaks and to protect from water intrusion under sills. They also chose high-performance, triple-pane windows, and the continuous, watertight EXTOSEAL ENCORS flashing system. We’re happy to report that Springhouse knocked the blower door test out of the park, with a fantastic 0.1 air changes/hour.

Passive House – Active Learning

One of the concerns about Passive House is that occupants do need to learn a bit about how to use it. But the idea that learning how to live in a Passive House is hard is a misconception. There’s a learning curve – just like there is with a new car, or a new phone operating system. But once you get the knack of a few things – like understanding the role of your HRV – a Passive House is just as easy to live in as any other. And because of the elimination of many complex mechanical systems enabled by the high performance of a Passive House, it becomes much simpler to live in than standard homes, and they certainly require less maintenance.

The cost savings are also significant. Even in the challenging Abercorn climate, this 1,900 ft2 home will cost only about $200 a year to heat, with a total energy budget of only $800. These enormous cost savings – coupled with other Passive House benefits, like a constant supply of fresh air and improved indoor air quality, along with the quiet provided by airtightness and robust insulation – will make Springhouse a uniquely safe, comfortable, and healthy home. Because of their attention to materials selection, Springhouse is also a model for ecological building design.

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7 Responses to Hooray for Double Standards: Passive House + LEED Platinum in Quebec

  1. Christon Kellogg August 17, 2017 at 11:11 am #

    Nice project!

    Would you share square foot cost?

    • Floris August 17, 2017 at 4:53 pm #


      Thanks for your question, we will reach out but dont’ know if we will be able to get SF cost.

    • Sarah Cobb September 7, 2017 at 8:33 pm #

      The house was $138/square foot before finishing which, in our case, was about $40/square foot.
      The garage was $100/square foot finished.

  2. Justin Huntington August 17, 2017 at 11:55 pm #

    This is an interesting roof assembly. It looks as though there is no roof decking, but instead latticework atop the trusses with a WRB in between, and standing seam on top. I see the ends of the latticework open at the fascia, which could be ventilation to the underside of the standing seam directly? This assumes, of course, NBCC allowing for standing seam to be installed sans decking when the panels are designed for it. So many questions. I’d be interested to lean more.

    • Sarah Cobb September 7, 2017 at 8:32 pm #

      The house was $138/sq.ft without interior finishing which, in our case, was about $40/sq.ft. The garage was $100/sq.ft finished.

  3. Floris August 18, 2017 at 4:33 pm #

    Justin, you can do this if using a metal roof with a gauge meant for skip sheating/intermittent battens – in that case the gap between the SOLITEX MENTO Plus roof underlayment and metal is indeed vented. This makes for a very good outward drying potential of the roof’s insulation as there is no vapor retarding plywood/OSB sheathing that retards vapor on its way out. Or course, as with every building, the structure has to be engineered properly, but this type of roof has been used by many builders and contractors using 475/ProClima materials with great success. ALso because the MENTO Plus is both a temporary roof as well as a waterproof subroof (for wind blown rain etc) under the metal for the life of the building.

    We have details of such roofs available here/ and feel free to contact us with questions at

  4. Sarah Cobb September 7, 2017 at 8:50 pm #

    The roof structure is raised heel scissor trusses with 30″ of dense-pack cellulose. The Mento went on top followed by 2x3s laid flat and vertical on the trusses, 1″x4″ rough hemlock furrings every 12″ horizontally and the tin (which was not standing seam but pretty much the cheapest galva roof we could find). We have a 16″ overhang and the soffits have screened gaps to provide venting. We ended up adding strips of furring in between the vertical 2x3s to push back on the cellulose so we’d have the circulation we wanted — absolutely key in our crazy climate, especially with the huge winter temperature variables we’ve been getting in the last ten or so years. The air barrier actually comes inside beneath the scissor trusses and connects to the interior vapour barrier so the whole roof is outside the envelope.

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