Canada's first Passivhaus points to the future of green building with wood. Second of three parts.
Canada's first certified Passivhaus is in Whistler.
It took three decades for the ideas embodied in the lone, landmark Saskatchewan Conservation House to return back home to Canada. And it took a group of Austrian businessmen leveraging the 2010 Winter Games to make it happen. The house itself may prove worth the wait.
Austria House, nestled just north of Whistler Village, is so well insulated that it needs no furnace. The 2,700-square-foot building requires less heat than is produced by a common household hair dryer and generates most of that meagre heating energy on-site.
The house itself now serves as a cross-country ski centre, where visitors can rent equipment or obtain directions to the Lost Lake Loop and other backcountry trails.
The way this particular Passivhaus was built also presents British Columbia policy makers with a trail map to the future of green building -- and points the way to new opportunities for the struggling B.C. wood products industry.
Shipped from Europe in containers
Canada's first certified Passivhaus was inspired -- provoked might be a better word -- by remarks Minister Colin Hansen reportedly delivered to a reception in Vienna during the build-up to the 2010 Olympics.
Europe was already home to more than 20,000 Passivhaus buildings at that time. Hansen was speaking to an audience that included some of the most experienced green builders in the world when he promised that the 2010 Winter Games would be the first "green" Olympics. When they finished chuckling, a group of Austrian builders saw an opportunity.
"They thought, 'Hey, we can show the world what green really is,'" said Matheo Dürfeld, a Whistler builder who worked on the house.
The Austrian Passive House Group was quickly formed. It included Sohm Holzbautechnik, a woodwork company that prefabricates Passivhaus buildings; Optiwin, a manufacturer of Passivhaus windows; and Drexel und Weiss, a manufacturer of heat recovery ventilators. Their plan was to prefabricate a Passivhaus in Austria, assemble it in Whistler, and rent it to the leading Austrian television network for use as a broadcast studio during the 2010 Winter Games.
"The intent of the building was not so much to show the Canadians what the Austrians can do," Dürfeld said. "Really it was more to show the Austrians what the Austrians can do."
Though prefab construction is not part of the Passivhaus standard, it has become a common method of construction in Europe. Austria House arrived in Whistler aboard six 40-foot shipping containers.
Dürfeld was hired to coordinate local construction. A log home craftsman who evolved into a builder of high-end chalets, Dürfeld and his meticulous crew chief, Manfred Haas, completed the construction.
"We didn't build the house," he said. "The Austrians sent a crew over to assemble it. We started the house for them. And after they left, we finished the house."
A soft-spoken Canadian of Austrian decent, Dürfeld is prone to self-deprecating humour. When asked why his firm was selected for the job, he quipped, "I don't know. Maybe it was only because we speak German."
In the ground: An insulated foundation
Passivhaus aficionados are obsessed with the reduction of what are called "thermal bridges." A thermal bridge is any hard material that readily conducts heat from the interior of the building to the outdoors (in winter), or vice versa (in summer). Picture the cooling fins on an air-cooled engine, or the concrete balconies that stud near every Vancouver condo tower.
"Thermal bridging is your big enemy when you are building," Dürfeld said. "The first lesson in thermal bridging is going to be in your foundation."
So while nearly every other Canadian building stands atop a concrete foundation in direct contact with the earth, Austria House stands on a concrete foundation poured atop ten inches of expanded polystyrene (EPS) foam. The foam also wraps around the sides of the foundation walls.
"This gives us in thermal mass inside the insulation," Dürfeld explained.
The air inside the house slowly heats (or cools, in summer) that thermal mass. In return, the thermal mass works to maintain a steady air temperature inside the house, rather than continually working to lower the indoor air temperature to that of the surrounding earth.
Standing atop the insulated foundation are 18-inch-thick walls that are more than twice as well insulated (R-50) as a typical British Columbia building. And atop those walls is an even more heavily insulate (R-70) roof.
But it's not just the thickness of the walls that make Canada's first Passivhaus unique. It's the way they are built. Just as veteran skiers dress in many thin layers of clothing rather than one thick parka, so the Austria House is constructed from a series of carefully designed layers.
Layer one: Solid wood mass wall
And in stark contrast to the way Canadians build, nearly every layer in this Austrian-built Passivhaus is made of wood.
As noted yesterday, the Passivhaus standard is less prescriptive than alternative green building systems like LEED or BuiltGreen.
Passivhaus doesn't tell builders how to build. Instead, it sets firm limits on the amount of energy a building is allowed to consume, then lets individual builders decide how to meet those limits.
Sohm Holzbautechnik, the general contractor that prefabricated the Austria House, not only met the standard, but did so by layering wood in ways that few British Columbians have imagined.
"The heaviest wood is on the inside," Dürfeld said during a recent tour.
Indeed, where nearly every Canadian builder installs sheets of gypsum drywall, Sohm Holzbautechnik mounted solid walls of spruce two-by-fours. The boards are stood vertically, and lined up one after another, so that only a two-inch side is visible. All of these boards are held together using patented diagonal wooden dowels, which eliminate the need for toxic glues or chemicals of any kind.
"That's not a Passivhaus standard," Dürfeld noted. "That's just the way this company prefers to build."
Like the insulated foundation, this attractive wall of solid spruce provides thermal mass that helps hold the building at a consistent temperature.
"This inside wall, the four inch mass wall, is your structure," Dürfeld said. "The rest is just a blanket."
Layer two: Plywood vapour barrier
Where Canadian builders place large sheets of plastic behind the drywall, the Austrians mount yet another layer of wood.
Austria House’s vapour barrier is built of plywood. Where one sheet of plywood joins the next, the seam is carefully taped.
"They have amazing tapes," Dürfeld said. "We have one tape we're all familiar with, the red stuff. They have different tapes for wood-to-wood, for wood-to-concrete. They have about five or six different tapes, depending on the product they are taping."
And while Canadian vapour barriers are typically punctured every few inches by staples, drywall screws and junction boxes, Passivhaus vapour barriers are sacrosanct. Wiring and plumbing is run inside the barrier (in the sold spruce wall), not through it.
"When we build dimensionally, we tend to penetrate our vapor barrier everywhere. A typical home probably has three to four hundred penetrations in its vapour barrier," Dürfeld said.
Not surprisingly, such buildings are not even close to airtight.
When subjected to a blower door test, which is designed to create a pressure difference of 50 Pascals between the interior and exterior air, a typical Canadian home might measure between four and six air changes per hour. (This is described as 6 AC/H@50Pa.) That's not ventilation; that's just leakage.
The R-2000 standard to which BuiltGreen homes aspire is 1.5 air changes per hour at the same pressure. The minimum Passivhaus standard is 0.6 air changes per hour.
Austria House rated only 0.26 air changes per hour.
"This is probably the most critical component," Dürfeld observed. "If you fail air tightness, you're simply not going to get the rest of it right."
More layers, more wood
The Austrian fetish for wood products extends to the outer layers as well.
Beyond the vapour barrier, where Canadian homebuilders install 2x6 studs (aka. thermal bridges) and fibreglass batt insulation, the Austrians install 2x12s and non-toxic insulation such as blown-in cellulose (a wood product) or mineral wool.
"The preference over there is for wood-based insulation," Dürfeld said.
The outside wall, where Canadian builders install yet another layer of plastic (such as Tyvek), the Austrians mount what they call defusion board.
"It looks like fiberboard. It's denser than a donna conna. But it can pass vapour," Dürfeld said. "Again, it's a wood-based product."
In Northern Europe, a (wood slat) rainscreen is attached to the diffusion board, and (typically wooden) siding is mounted on the outside.
The Whistler house, however, is clad with distinctive black cementations siding similar to Hardiplank. This, too, was provided by one of the building's sponsors.
Windows that shut tight
Windows are a notable exception to the Passivhaus standard's performance-based approach. This is because there is virtually no possibility of meeting the Passivhaus air tightness requirements with the relatively poor quality windows sold in North America.
"The windows are absolutely key," Dürfeld said. "That can be the biggest heat loss in your house."
In Europe, the Passivhaus standard specifies windows tested and registered by the Passivhaus Institute or affiliates. These windows are typically constructed from three panes of coated glass separated by two gas-filled chambers, each of which is more than a half-inch thick. Also, the window frames are exceptionally airtight, typically incorporating two ore more rubberized gaskets. The frames are also quite thin.
"The frame is your enemy, because the frame is less efficient. There's more thermal conductivity through the wood than through the glass and the air," Dürfeld said.
The doors are similarly constructed. And all are sealed to the vapour barrier with more specialized tapes.
"To my knowledge there are no North American made wooden doors or windows that will meet the Passivhaus standards," Dürfeld said. "This could be a business opportunity for the right company."
Buildings that breathe easy
One of the most common misconceptions about Passihaus and other airtight buildings is that they are stuffy. The truth is that because they are actively ventilated, they tend to harbour significantly higher indoor air quality than comparable buildings.
The name Passivhaus was selected to describe the intention that such buildings eschew "active" heating (such as a boiler or conventional forced-air furnace) or air conditioning systems. But nearly every Passivhaus building does include an active ventilation system called a heat recovery ventilator, or HRV.
An HRV is a device that draws cold air from the outside through one side of a series of baffles that act as a low-pressure heat exchanger. Indoor air passed through the other side of those baffles as it is expelled from the building. Thus the indoor "heat" is "recovered," as fresh air entering the building is warmed.
Heat recovery ventilators typically operate quietly and blow air much more gently than a forced-air furnace. The airflow is barely perceptible, but by running continually. In Austria House, the air is completely exchanged every 90 minutes.
"It's constant. You can never shut this thing off," Dürfeld explained.
The final 10 per cent
Superinsulation and extreme air-tightness are the core of the Passivhaus approach, and provide most of the energy savings. Dürfeld estimated that Austria House uses about 10 per cent of the energy of a comparable building.
"During construction, we were able to heat the house with one of those little 1,500-watt ceramic heaters," he said. "One day I remember, it was about seven below outside. Just really, really cold. But all your interior surfaces, floors ceilings windows walls, were all within about a degree and a half of each other."
Austria House generates much of what little heating energy it requires from a low-tech ground-source system.
Dürfeld and his crew buried three long ABS plastic hoses beneath a 20-meter-long yard in front of the building. Dürfeld described them is "giant slinkys," and said they were placed about two meters deep then covered with gravel.
The fluid that runs through these hoses is cooler than air in summer, and warmer than air in winter. It runs through a compressor, thereby creating about four kilowatts of energy. That's enough to heat the building's hot water and at times further raise the temperature of incoming air flowing through the HRV.
Lost Lake Passivhaus
Austria House worked for its builders. As seen on Austrian TV, the 2010 Winter Games looked at times like an infomercial for the Austria Passive House Group. When the games were through, they gave the house to the municipality of Whistler for use as a cross-country ski base.
The building has since been renamed Lost Lake Passivhaus.
Lost Lake Passivhaus -- nee Austria House -- is working for Whistler, too.
"We always had the vision of trying to leverage some sort of a country house in this location to help support our cross-country operation," said the city's Roger Weetman.
"It worked out fabulously," he continued. "From a sustainability perspective, it was a perfect marriage, right? It was exactly in line with what Whistler is trying to do."
And the project worked well for Dürfeld.
"This is the most interesting thing I've done in all the years I've been here," he said. "It's like taking a car from 30 miles per gallon to 100 miles per gallon."
Dürfeld's company is headed in "a whole new direction" in the wake of the Austria House project. (More about that tomorrow.)
"We're going to reinvent the envelope we live in," he said. "And then we can recreate how we build."
What remains to be seen is whether the lessons embodied in Austria House will be learned by the British Columbia wood products industry -- or, like the Saskatchewan Conservation House, politely forgotten.
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