Cottonwood House

Passive House passes cold-climate test

The Cottonwood Passive House is one of the first homes in Alberta built to the Passive House standard. Located in a developer subdivision, the owners and project team hope to demonstrate that exceptional energy efficiency is a realistic and achievable goal, even in a suburban context.

By David Zeibin

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The Cottonwood Passive House sits on a sloping site at the edge of Fort Saskatchewan, north east of Edmonton, enjoying views toward the North Saskatchewan River valley. Designed as a retirement home for my parents, Jim and Emilie Zeibin, the house can function on one level, with amenities such as main-floor laundry and a large, elevated deck.
The project began in early 2011 when Jim and Emilie fielded the idea of a net-zero house. Having lived in various cold-climate communities across the western provinces [including Fort St. John, BC and Rainbow Lake, AB] during a career as a chemical engineer, Jim was tired of living in cold, drafty houses and was conscious of the quantity of energy used by single-family residences.

Unsure about the possibility of needing to install a large photovoltaic array in a net-zero scenario, I suggested they look into the German Passive House standard as a first step toward the similar requirements of a net-zero effort: super-insulation, extreme airtightness, high quality windows and doors, and so on.

At the time, Passive House was quite new in Canada, with only about four projects underway across the country and the newly formed Canadian Passive House Institute [CanPHI] just beginning to offer formal training. Jim and I attended CanPHI’s five-day/40-hour intensive training course in October 2011, while initial planning and concept design started around the same time.

Design
The main floor of the house is roughly organized along a central circulation axis — beginning at the main entry, through a hall into the combined kitchen/living area, and out to a large covered deck. The house’s footprint is kept compact to minimize total envelope area and thus minimize heat loss. Primary living spaces – bedrooms, living rooms, kitchen – are oriented toward the south with generous glazed openings to capitalize on passive solar gains. The walk-out basement is configured to allow the possibility of a standalone guest suite in the future.

Without many North American precedents and a lack of Passive House-quality building materials, the team relied on the well-documented Naugler House in New Brunswick [http://www.nauglerhouse.com/, also published in the Fall, 2013 issue of ecoHouse Canada] and mimicked some of their foundation and wall assembly strategies.

Targeting the Passive House standard in Edmonton’s relatively harsh climate resulted in foundation walls surrounded by 12” of EPS insulation and 16”-thick double-stud walls with an additional 3.5” insulated service cavity inside the taped OSB air/vapour barrier. The roof employs 30” of loose-fill blown-in cellulose insulation and a carefully taped and sealed polyethylene air/vapour membrane.

A heat recovery ventilator [HRV] within the electric preheater drives the ventilation system with ducting installed with the 14” deep main floor joists. Space heating is provided by a zoned hydronic baseboard radiator system, with hot water generated by a heat exchange loop from the domestic hot water system, which is driven by a high-efficiency condensing gas boiler. Thermostats with occupant-override controls are located around the house and allow the hydronic system to deliver hot water to the radiators only where needed.

To control costs and accommodate the limited availability of trades familiar with low-energy construction, the team attempted to use as many conventional techniques as possible such as typical wood framing using wood I-joists, prefabricated roof trusses, and site-framed walls, along with common materials such as rock wool, fibreglass batt and blown-in cellulose insulation, OSB sheathing, fibre-cement cladding, and asphalt shingles.

Acting as general contractor, Jim undertook significant portions of the construction himself, including particularly sensitive scopes such as air sealing the combined air/vapour barrier, insulating the envelope, and participating in the window and door installations. With the Passive House course background and his continual presence on site, he understood the Passive House science and principles, and was able to guide trades who weren’t necessarily familiar with ultra-low energy construction.

  • Project Credits
    Owner Jim & Emilie Zeibin
    Architect David Zeibin Architect AIBC MRAIC LEED AP BD+C
    Structural Guy Blood, PEng
    Mechanical Stuart Fix, P.Eng. [ReNü Building Science]
    Construction Consultants Peter Amerongen [Habitat Studio], Lahnert Larsen Design Fabrication, Eric Del Brocco [Delrick PM]
    Photos Yesan Ham, Jim Zeibin, David Zeibin
  • Materials
    Wood-frame construction with EPS insulation on poured foundation and below footings, cement-fibre siding, mineral wool and cellulose insulation. Entry doors by EuroLine . Hydronic baseboard heaters are Rescom 2100 supplied by a condensing boiler. HRV is a Zehnder Novus 300, and Zehnder air distribution products, such as ComfoTube. Cork and linoleum flooring, and primarily LED lighting.

David Zeibin Architect AIBC MRAIC LEED AP BD+C is based in Vancouver. More information: http://cottonwoodpassivehouse.ca/design/ . Emilie Zeibin’s thoughts on “Why we chose to build a Passive House” http://cottonwoodpassivehouse.ca/our-story-why-we-chose-to-build-a-passive-house/

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