Tag Archives: passive house

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 -20ÂșC 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.


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Hallway Storage

Over the last couple of months, Jeremy Balint, one of our talented local woodworkers, has been building the storage in the entrance hallway. It’s been an empty space since the house was completed, so it’s great to finally get this done.

The storage, for coats, hats, shoes and other outdoor gear, is constructed in a similar way to which Jeremy made our bookshelves – basically, a series of birch-ply boxes and shelving units which he made in his workshop and then connected together and fastened to the walls onsite. The whole thing was then faced in fir and we put on a fir sliding door in a modern barn style. It’s designed so that one half of the main hanging space is always open, and there’s an inside light so you can see what you’re doing. It also incorporates a relatively enclosed space for the cat’s litter tray roughly where it’s always been so the cat doesn’t get too confused!

After the whole structure was put together, I finished all the fir with Tried and True Varnish Oil, which is a mixture of linseed oil and a pine resin-based varnish. It has to be rubbed in carefully but it produces a really satisfyingly deep and rich sheen. At the same time, I lightly sanded and finished the cherry top on our bookshelves and the fir handrail on the stairs, both of which had been left unfinished until now.

 

 

Carpenter Bees

A Carpenter Bee Burrowing

One thing I really hadn’t anticipated would be a problem for us was Carpenter Bees. These large bumblebee-like creatures have a liking for old softwood trees or untreated softwood lumber, in which they burrow, making 1/2cm diameter holes often more than 1m long. They then lay their eggs in them, leaving enough pollen to feed the larvae that will eventually emerge. Our entire place is built out of softwood, however most of it is either CLT, which they don’t go for, or safely treated or under layers of other stuff. However, for some reason, Carpenter bees don’t seem to care about the Sansin natural finish we’ve used everywhere on the external timbers, and in particular, the long non-CLT beam that holds up our porch has attracted their attention. There are all kinds of folk remedies out there, including citrus oils, but none of these seem to bother them that much. They are pretty easy to kill individually but I don’t like to do this as, like all bees, they are getting less common and we need them for pollination. So it seems like the only solution is to have the exposed woodwork sprayed with an insecticide, as recommended here.