Concentration of CO2 in the Atmosphere

Net-Zero Home Emerges from Sustainable Lifestyle

The 2,600 square-foot home boasts a blower-door test rating of 0.59 air changes per hour (ACH), compared to a similar home built to minimum local standards which would typically have a of about 3.5 ACH. (Courtesy images)

Dan Vastyan

For decades, Janet Armstrong and Lloyd Davies lived and breathed the sustainable lifestyle. Their way of life ties to the example set by Janet’s father, who built the first solar house in Vancouver, BC, in 1978.

Armstrong and Davies lived in their first home in Vernon for 35 years, making many energy-conscious improvements as time passed. After retiring, they wanted a home that required less maintenance and offered an even smaller carbon footprint.

The couple wanted the 2,600 square-foot home to blend in with others in the neighborhood while being supremely energy efficient and sustainable. The craftsman- style residence includes an in-law suite, greenhouse and wrap-around deck.

Rainwater from the standing-seam roof is used to water vegetable gardens, and a 35-panel, 10.85 kW solar array provided 103% of the home’s total energy needs last year, making it a net-zero residence. The solar PV is just the beginning of its eco-friendly amenities.

Tight construction

Stonebridge Net Zero Construction Ltd. built their dream which included the Japanese aesthetic of making every square inch of a house count.

The earth tubes terminate in a small, open-air
structure in the backyard.

The home was to be extremely comfortable, functional and efficient, while also providing performance feedback through its control system.

Hardie Plank fiber cement siding is used on the home’s exterior, along with a standing seam metal roof. Exterior walls are double thickness with a half-inch gap between inner and outer studs to minimize thermal bridging. Blown-in cellulose insulation fills the stud bays and all wall penetrations were sealed for an airtight shell. On the outside of the plywood sheathing, Roxsul Comfort Board insulation was applied, bringing the exterior walls to roughly R-38.

More than six inches of Styrofoam insulation paired with a double vapor barrier are used under the home. Two-inch dense foam was used on the inside of the footings to isolate the slab. In the attic, an R-60 layer of cellulose insulation was blown in. All exterior doors and windows are triple-pane, supplied by Innotech Windows + Doors, Inc., a manufacturer in British Columbia.

The ultra-tight construction provides a blower-door test rating of 0.59 air changes per hour (ACH). A similar home built to minimum local standards would typically have a rating of about 3.5 ACH.

Because a home needs fresh air infiltration to maintain a healthy living environment, the house has a fresh air system that includes a heat recovery ventilator (HRV) tied to a series of four “earth tubes.” These 10-inch diameter, high density polyethylene tubes are buried between seven and nine feet deep along the foundation of the home. The soil temperature in the area remains at roughly 50°F (10°C), conditioning fresh air in the winter. It also provides the only source of AC in the summer. This system, along with the home’s graywater recycling system, was designed by Trevor Butler, P.Eng., at Archineers Consulting Ltd. in Kelowna.

The indoor termination of the earth tubes, providing the only source of air conditioning.

In the winter, the HRV further warms incoming fresh air by transferring heat from the outgoing air. This fresh air system runs continuously. Discharge air from the HRV is blown over the outdoor portion of the heat pump, providing yet another source of waste heat utilization.

“An energy study revealed that the home is one of the most energy efficient residences in Canada,” said Davies.

Total control

A 34,000 BTU Maritime Geothermal air-to-water heat pump supplies hot water to 10 zones of in-floor radiant heat. The basement slab includes hydronic tubing. The home’s wooden structure is rated to carry a three-inch slab of concrete on the second and third floors. There, hydronic tubing was fastened on top of the subfloor with concrete poured over.

Everything in the home is controlled by an extensive tekmar control system. Thermostats control the radiant floor heating temperature and air cooling temperatures. A House Control operates the air-to-water heat pump and regulates the supply water temperature based upon outdoor reset.

Providing power to the thermostats and hydronic zone valves is a Wiring Center, and a tekmar Net Gateway provides internet connectivity through a mobile app and website.

Additionally, 35 tekmar sensors are used to measure and monitor building performance. These sensors, which are connected to a data acquisition system, are scattered throughout the home; in the floor, in the walls, outside, etc., providing real time feedback.

Uniquely British Columbian

A cold room is used to store fresh fruits, vegetables and wine. It’s brilliantly cooled by 39°F (4°C) discharge air from the home’s Rheem hybrid heat pump water heater. The room remains at 37°F (3°C) in the winter and 50°F (10°C) during the summer. A hot room with a large window on the second floor provides passive solar energy on sunny days no matter the season, and warms a small greenhouse. Warm air generated in this room is circulated within the house by the HRV. There is also a passive solar hot water panel inside the hot room that provides preheated water to the water heater.

The home features the first locally-approved gray water diversion system, often called “purple pipe,” which reduces the sewage flow by 60% during spring, summer and fall, when the landscape irrigation system runs.

“Lots of hard work and sweat has built a wonderful home,” said Davies. “It’s warm where it needs to be, cool where it should be and very quiet because of the great windows, doors and insulation. Our costs to live here are very modest. We have no gas or electric bills. Our only expenses are city utilities, house insurance and city taxes. We love it.”

Dan Vastyan is PR director and writer for Common Ground, a trade communications firm based in Manheim, PA.

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