Author Archives: David

About David

I'm David Murakami Wood. I live on Wolfe Island, in Ontario, and am Canada Research Chair (Tier II) in Surveillance Studies and an Associate Professor at Queen's University, Kingston.

Old house demolition

Our old house is finally being demolished… so next year we can finally start landscaping.

It begins…
Demolition is a lot quicker than construction (photo courtesy of Sus Bowers)

There’s a lot I could say about demolition and the environment. We really wanted someone to ‘deconstruct’ rather than demolish the house, but we could not find anyone to do this. Most did not reply. One guy came and had a look then never got back in touch. Others were busy. The demolition company we ended up using, Environmentall, has saved the windows for Habitat for Humanity but not much else escaped the machine. They do, however, sort the remains and recycle whatever they can. I don’t know how much that is in practice.

Looking after your door locks

The other day I posted about one of several probably entirely preventable problems we’ve had over the last couple of years since moving in – the problem of HRV operations at low temperatures. The second of these problems also has to do with low temperatures, but this time relating to door handles and locks. It’s not something I would ever have thought about before building this house, since we never used to bother locking our front door in our old house, but since we now have a front door that automatically locks when you leave, door locks have become an important topic, especially in winter.

Our front door, a passive house certified, super-insulated model made by a company called Tarredo in Germany, is the single most expensive item in the house. It’s also very secure: you can’t just leave it unlocked. And the only way of opening it is with a key – and there is no turnable handle or back-up. This might not seem like a problem, but the lock is also a cold bridge to the outside, and because of the frequent high contrast in temperatures between the inside and outside, we sometimes get a significant build up of ice in the lock itself.

We’ve already had to replace the lock spindle once, as last winter it ‘cold-welded’* to other parts of the lock and sheared off. That’s right, it broke in half! I only recognised what had happened because this is an occupational hazard for cyclists – winter temperatures can often result in seat posts becoming chemically bonded to the inside of the frames of bikes. It makes me wonder whether these lock mechanisms have ever been tested down to the kinds of extreme winter temperatures we get in Canada (as low as -30ºC here).

The solution we’ve come up with is threefold:

1. grease the spindle with some heavy grease that works at low temperatures;

2. spray de-icer into the lock periodically in winter; and

3. Simply cover the lock itself to prevent the passage of moist air from outside to inside. I made a neoprene and duck tape cover, which works just fine.

*yes, I know that technically this is not ‘cold-welding’ in the sense of metals combining in a vacuum.

HRV Fan Failure: the importance of pre-heating in cold climate zones

We’re in our third winter in the passive house (the second full winter, I guess, since we were only in for part of the first and a lot still needed to be done back then). Several issues have emerged, which are all things that are fixable, but which in retrospect could and should have been prevented. The main one of these is that about a month ago, one of the fans in our HRV failed suddenly, which left us without ventilation in the middle of winter. Up to this point, the Zehnder HRV* has been completely hassle-free – you’d hardly have noticed it was there at all.

This is when it suddenly turns out to be very important that there is a reliable local dealer for your HRV company… and, there isn’t. Pinwheel, who supplied us our system, ceased being an official Zehnder dealer pretty soon after we got our system and despite there being officially named companies that have some affiliation in the province, none of them actually supply or repair Zehnder. Luckily, Zehnder North America have awesome people in their main offices who are prepared to go the extra mile for a customer.

I chatted to a couple of different people, the first, Joe from Operations, about the possible causes of the failure and what we needed. Zehnder agreed to send us a replacement fan immediately with no charge. Excellent. But then what to do about the installation? Well, basically, they got another guy, Gary, the Training and Service Manager, to walk me through it. Yes, I did it! it wasn’t that hard, as it happens, although there were some electrical circuit operations to perform that had to be done exactly right and safely, but I wouldn’t have been able to do without him. I’m pretty confident I could do it again now, if I had to. Gary – you’re awesome!

As to why this happened… well, it’s highly likely that it was something to do with the low incoming air temperature. We noticed when we were installing the system that Zehnder HRVs are not guaranteed below a certain temperature. Apparently Zehnder would never recommend installing one without a preheater, but no-one involved in our original installation – not our passive house advisor, not the dealer and not their contact at Zehnder at the time, ever mentioned this or suggested including a pre-heater. Everyone seems ‘surprised’ now that it somehow didn’t happen. So, a take-away for anyone building a passive house in these cold climate zones: you need a pre-heater for your HRV — don’t forget it or think you can get away without one.

Anyway luckily for us, Zehnder has recently changed the way it does pre-heating for its HRVs anyway. Instead of an internal pre-heater, they now supply an external model that sits in the intake duct. So, we’re installing on of those, and hopefully we’ll have no further problems with fan failures.

I’m still thinking about the implications of all this. A sudden HRV failure makes you very aware of just how much the passive house concept depends completely on this mechanism, and however reliable the mechanism you have, this dependency is a large weakness, a major lack of resilience. On the other hand, we did find that ventilating the house by opening windows for half and hour a day works even in winter when it’s -20ºC outside without cooling down the house too much. We’d been super-paranoid about opening doors for even a few seconds before and, actually, it was fine. We also used a dehumidifier to get rid of excess moisture.

Anyway, a big thank-you to Zehnder North America for their support. They really are a great company – if only a decent Ontario company would take up the challenge of being a proper dealer and servicing agent…

*Zehnder Comfoair 200 UL (Luxe) ERV. You can see more about the system installation here.