They worked so hard to meet the Passivhaus target and they missed it.
There are not a few people out there who think that the Passive House or Passivhaus concept sets an "arbitrary energy target that ignores everything else." Another critic once called it "a single metric ego-driven enterprise that satisfies the architect's need for checking boxes, and the energy nerd's obsession with BTUs."
The Ecoflats failed to meet that target. Many people will say "so what, they did a great job and it is arbitrary anyway." But the fact that there WAS a target drove them to find out where every air leak, big and small, came from. It drove serious research, experimentation, testing and designing solutions to problems that come up in every renovation.
They discovered that they shouldn't have trusted their window manufacturer, that the windows needed latches top and bottom if they were really going to seal.
Tom discovered "leaking in places I didn't know existed." They developed new ways to seal around joists and to install air barriers.
Air barriers are misunderstood and often ignored; when I practiced architecture they weren't even in the codes. As Green Building Advisor notes,
Building scientists have learned a great deal about air barriers since the 1970s. They now recognize that air barriers are key to how long a building will last, how much energy it will require to heat and cool, and how comfortable its occupants are going to be.
John Straube may be a Passivhaus skeptic but he believes in a good air barrier and is quoted in Green Building Advisor.
“The only way you can know for sure that the air coming into a house is clean is to know where it's coming from,” Straube writes. “People who say, ‘I want my house to breathe’ are really saying, ‘I want to rely on the mistakes that were made by the plumber and the electrician to provide me with fresh air.’ That's exceptionally dangerous. Any air that enters a house through leaks in the building envelope may be loaded with pollutants. The dead squirrel in your attic and the SUV idling in your garage are not going to provide you and your family with fresh indoor air.”
Clearly, everybody agrees that controlling air leakage is of paramount importance. In a townhouse divided into three apartments it is even more important, since dust, bugs and smoke can travel through those air leaks. (marijuana is being legalized in Canada in July, so you really want a good air barrier, that smell travels!)
Which brings me back to my original point. Tom had a target, aiming for the Passivhaus standard of 0.6 air changes per hour (ACH) He chased every leak, and did everything he could, and got to 1.18 ACH. He failed. (UPDATE: but not by much, see update at bottom)
And it isn't actually a big deal, the difference is going to cost him all of $29.93 per year in additional heating and cooling. And he probably spent a hundred times that chasing down the leaks to get it to that point. But who knows what it might have been had he not had a target? Where would it be? 2ACH? 3? Who knows, but it would certainly be higher. He might have been happier to be able to call his project a success instead of a failure. But he learned really important lessons.
Perhaps the biggest lesson was learning that one should worry not about WHERE the air barrier is, but WHEN. You have to take this issue seriously and make room for it, or you will keep coming back to look for new leaks and problems.
Having a tough target drives innovation, creativity and knowledge, which they will apply to their next Ecoflat renovation. As for missing it, I will end with Robert Browning, who is a bit more poetic than John Straube: "Ah, but a man's reach should exceed his grasp, Or what's a heaven for?"
UPDATE Readers in the know about Passivhaus advise that I should point out that there is the EnerPHit standard for renovations and the PHI Low Energy Building Standard "suitable for buildings which do not fully comply with Passive House criteria for various reasons." These standards allows for 1.0 air ACH at 50 pascals of pressure, so Tom was really, really close.