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.