Architect Terrell Wong of Stone’s Throw Design is certainly passionate when it comes to sustainable/green architecture. More recently, she’s found a new – and related – love in the “very fledgling industry” based around the German Passive House movement, a relatively new, ultra-strict set of energy-efficiency guidelines first put to the test in Darmstadt in 1990.
While the Internet was full of international examples of Passivhaus Institut-certified buildings (and the U.S. equivalent, PHIUS), very few Canadian examples were floating around in cyberspace or elsewhere, so Ms. Wong, a co-founder and the first president of the non-profit Passive Buildings Canada, decided to write Passive Buildings in Canada.
“It’s sort of like getting under the sheets and seeing what’s going on,” she says with a laugh. “I used my network to beg and plead everybody who is in the middle of a project, working too hard, to give me all the information they have.”
And while it’s not a huge book – she calls the slim 55-page hardcover “a snapshot” – each of the 13 projects profiled contain a few paragraphs of background information, technical specifications, a beautifully drawn section plan, and, perhaps most importantly, the names of the professionals involved. Large photos illustrate that a home built to Passive House standards can “be designed in any style, shape [or] form.”
It’s true: The first home featured, the Cook Residence, designed by Ms. Wong and built by Aerecura, has walls made of rammed earth (featured in Globe Real Estate in February, 2012), while a few pages over, a duplex in Whistler sports prefabricated wall panels. Further into the book, there is a straw bale cottage, and an Edmonton high-rise complex containing 209 units.
No matter how different the method of construction, however, each sips about one-tenth the energy of the average home. Speaking of which, how a home becomes a Passive House boils down to three main ingredients:
It allows 0.6 air changes per hour at 50 pascals (or less). To calculate this, a blower door test is conducted, whereby the home is depressurized and then repressurized to determine how much air leaves or enters via unseen points. “So it’s really air-tight,” offers Ms. Wong. “The new code this year I think has it around three or four changes per hour, but you’re not required to test it, and most houses of 10, 20, 30, 40 [years] or older, those houses are probably 10-plus air changes per hour.”
The home’s heating or cooling load must be at or below 15 kilowatt-hours per square metre. “So, on average, a household would use between 100 and 150 kilowatt-hours per metre-squared, so it’s one-tenth less than your average existing home.” Newly constructed, non-PH houses, she adds, are “getting better.”
The most important number is a home’s primary energy load, which must clock in at 120 kWh per square metre or less. This includes energy lost during delivery. “For every kilowatt we use in a house,” she explains, “we use at least another, if not two, for it to get here in terms of line losses and wastage and things like that.” While clearly beyond the homeowner’s control, “we can make a choice between one energy over another based on how much loss is between us and the primary source,” Ms. Wong continues, “so either solar or, in some situations, natural gas makes way more sense than electricity.”
To get a home Passive House-certified is a somewhat lengthy process. A preliminary construction design using PHPP software (Passive House Planning Package) is sent to a licensed PH examiner (there are many in North America) to get preconstruction approval. Then, after the home is built, there is on-site testing done to verify that the results match the estimates.
That’s not to say retrofits of older homes can’t qualify. On page 32, Ed Marion’s Oakville home – once a 1950s one-storey brick bungalow and now an energy-saving two-storey superstar – proves that “anything is possible” with the right budget. And while retrofits are “more expensive by far than new builds,” Ms. Wong says that in cases where a homeowner is planning to take things down to the studs during a renovation anyway, it only makes sense to shoot for Passive House qualification.
But, she cautions, the Passive House standard is not a be-all and end-all. Not all houses can face south for free solar heating, and many existing homes will never meet the rigorous requirements without sacrificing much of their architectural integrity.
“For my whole life I’ve been looking towards finding a way to get to lower energy, and this is just one of those ways,” Ms. Wong finishes. “There’re lots of energy efficiency programs across the world … but the path in which you go towards Passive House will be able to reduce your energy, and in my house it was 75 percent.
“So you can use that path to get to your own destination.”
Passive Buildings in Canada can be purchased at blurb.ca or at Ms. Wong’s website, stonesthrowdesigninc.com
Editor's note: In the initial online version of this story the photo depicting the Whistler, B.C. duplex was incorrect. This version has the correct photo.