Canada’s Northernmost Passivhaus
Should it win certification, the house would become the most northerly Passivhaus in the country and one of only a few in the province
Work should be wrapped up this fall on a 1,895-square-foot home in Fort St. John, British Columbia, that is on track to become Canada's most northern certified Passivhaus residence.
Fort St. John, a 16-hour, 760-mile drive northeast from Vancouver, British Columbia, was established as a trading post in the late 18th century, and it still sees plenty of people traveling through on the Alaska Highway. These days, Fort St. John calls itself "The Energetic City," reflecting the region's rich natural resources of oil, gas, and forestry.
The municipal motto also seems an apt description of the city's plans to develop a mixed-use neighborhood including more energy-efficient buildings on a 91-acre parcel of city-owned property. The house nearing completion at 9904 94th Street is a sort of test kitchen where new technologies and construction practices could be worked out.
The city-owned house was designed with prefabricated wall and roof components by Marken Projects Design + Consulting, a firm specializing in high-performance buildings.
In addition to being the farthest north, Marken says the project also will become the first detached single-family residence in the province of British Columbia. Passivhaus construction, however, isn't entirely new to the province. Germany's Passivhaus Institut lists a "semi-detached house" built in 2012 in Whistler, which also was designed by Marken. And GBAGreenBuildingAdvisor.com's Richard Defendorf described a two-unit house built to Passivhaus standards in Whistler in time for the 2010 Olympic Games in a blog post in 2009. That project also is listed as certified by the Passivhaus Institut.
A challenging environment for Passivhaus construction
Certified or not, meeting the Passivhaus standard for heat and energy consumption is no walk in the park in Fort St. John, which posts an average of more than 10,000 heating degree days a year and sees mid-winter temperatures plunge to 30 degrees below zero F.
Designers specified a two-layer wall system consisting of an inner 2x4 service wall filled with mineral wool insulation and an outer wall of 11 7/8-inch I-joists on 24-inch centers filled with dense-packed cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection.. The wall assembly has an R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of about 56. Offset I-joists and 2x4 studs minimize thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. . (GBA senior editor Martin Holladay wrote about this home's walls last year in an article called The Klingenberg Wall.)
A layer of 5/8-inch oriented strand board on the exterior side of the 2x4 wall provides the air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both.. Exterior sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. consists of 5/8-inch fiberboard.
The slab assembly includes a finish floor of wood or tile over 1 inch of expanded polystyrene insulation (EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest.), 4 inches of concrete, and an additional 11 1/4 inches of EPS insulation, for a total R-value of about 52.
Below grade, perimeter walls are Fox Blocks insulating concrete forms with an 8-inch-thick core of concrete sandwiched between layers of 2 5/8-inch thick EPS insulation.
Roof panels are made with 16-inch I-joists insulated with dense-packed cellulose plus a 2x3 service ceiling layer insulated with mineral wool, for an overall R-value of about 70.
As of the June 24, the results of blower-door tests for airtightness were still pending.
Mechanicals and other sustainable building features
The three-bedroom, 2 1/2-bath house is all-electric. Other building details provided either by the city or at a blog on the project include:
- Domestic hot water from a 50-gallon Rheem heat-pump water heaterAn appliance that uses an air-source heat pump to heat domestic hot water. Most heat-pump water heaters include an insulated tank equipped with an electric resistance element to provide backup heat whenever hot water demand exceeds the capacity of the heat pump. Since heat-pump water heaters extract heat from the air, they lower the temperature and humidity of the room in which they are installed. .
- A rooftop solar array of 12 panels with a total rated capacity of 2.8 kilowatts. Planners estimate the system will generate 3,500 kWh of electricity per year, roughly one-quarter to one-third of estimated demand.
- Heating and cooling with a Mitsubishi Mr. Slim ductless minisplit system. There are two heads, one on the first floor with a rated capacity of 18,000 BtuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. /hour, and another, rated at 9,000 Btu/hour, on the second floor. Marken estimates the heating and cooling costs at between $200 and $400 per year. The house also has a heat-recovery ventilator(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. .
- Triple-glazed windows manufactured by Optiwin. GlazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. in the Alu2Wood windows has an R-value of 7.8 and a solar heat gain coefficient(SHGC) The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. of 0.52, according to Rogers.
- Sustainable building features include low-flow plumbing fixtures, regionally sourced and recycled materials were possible, lumber certified under the Forest Stewardship Council(FSC) Nonprofit organization that promotes forestry practices that are sustainable from environmental and social standpoints; FSC certification on a wood product is an indicator that the wood came from a well-managed forest., and native landscaping and permeable paving
The city becomes the general contractor
The city had not intended to build the house itself, lead designer Ayme Sharma and Marty Paradine write in the Marken blog, but after the construction documents were complete a request for proposals drew only a single response.
"The construction market is so busy in Fort St. John that there were not many builders interested in taking on the challenge of building something new," they write. "Developers in Fort St. John are most often focused on constructing single-family homes as quickly as possible to accommodate job growth in the oil and gas sector."
The city wasn't discouraged as much as it was motivated to show that Passivhaus construction was feasible in northern British Columbia, and that builders who knew how to pull it off would hold a competitive advantage.
Once the house is complete, the city will monitor its energy performance and use it for open houses for one year, then sell it.
"During construction, the project has already been used as a demonstration to teach the local building community about Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. construction and low-energy building design," the blog says. "There have already been signs of success in breaking down local preconceptions about energy efficient homes."
No overnight conversion to Passivhaus
Fort St. John City Manager Dianne Hunter doesn't expect this single Passivhaus project will convert either local builders or homebuyers to super energy efficiency overnight.
"It's about baby steps," she said, "starting slow."
Fort St. John is located in an energy-rich part of the country where people aren't expected to care very much about efficiency, she said, but that made it all the more important to the city to demonstrate otherwise as it looked for ways to develop the city-owned tract.
"We felt we had an obligation to show good stewardship of our resources," she said, and despite some of its frustrations, the Passivhaus project was a good place to start.
- City of Fort St. John
- Ken Rogers
Fri, 06/27/2014 - 20:25
Wed, 07/02/2014 - 10:23
Thu, 07/03/2014 - 22:21