We have received a copy of Anthony Mach’s final report on our place, part of a comparative study that also looks at another passive house project in Peterborough, Ontario. We’re not going to comment on the Peterborough project because we know very little about it and it’s very different to ours so, with Anthony’s permission, I will just highlight some parts of the report as it relates to this house.
Anthony’s report compares our Passive House to the new highest Canadian code standards. Bear this in mind, because the average Canadian (or US) house wouldn’t have been built to anything like those latter standards, and as for the average older house on Wolfe Island… well, let’s just say, you could probably punch a hole through the wall of many houses here, our old one included!
I think Anthony has been somewhat conservative with his estimate of the R-value of the walls and ceiling, which based on the whole assembly (including the CLT, which has an R value of 4-5 on its own, and siding) would be nearer 50 in my view. But conservative estimates are better than exaggerated claims for testing efficiency. This leads to some estimates for the house’s performance:
I’m also surprised by how much heat loss there is through the walls in these estimates, but apart from my feelings about R-values, I don’t have any basis for challenging this – it just seems like more than I would have expected. But the important thing is that our energy consumption is reduced dramatically.
I think here there is a little more erring on the side of conservatism here – basically Anthony has estimated the energy consumption of our appliance and lights to be the same as the 2017 Code standard, but we are using all LED lighting now – although we weren’t all the time when the measurements were taken in the winter as the electricians had just used a whole range of conventional bulbs – and we have fewer, smaller and more efficient appliances compared to the average household. We will have to test this empirically through the year via our bills! Anthony’s current estimate for our annual electrical bills has them at almost half the best you would get from a 2017 Code-standard house:
Of course, one of the problems with bills is that you can only reduce them so far: the majority of our bill is not use charges but fixed fees and delivery charges, over which we have no control, unless and until we are totally off-grid, which brings us to…
Green House Gas Emissions
On Green House Gas emissions, I would imagine that once we’ve installed the Solar Thermal and Solar PV panels (probably this summer, although it depends on costs), and possibly some other wind-based generation, this will further reduce our electrical draw draw from the grid and our costs, and therefore also our GHG emissions. Our eventual aim is to have zero energy bills and net zero GHG emissions.
You can see more detail about the winter temperature and humidity in the preliminary results. While, as Anthony notes, we found the house perfectly comfortable over the winter, I think the house will be a little warmer next time around. Because it was uninhabited until late November and there was no heating for a while after that, the house never really built up the sustained warmth that would thereafter be preserved to a greater degree by the insulation etc. We shall see!
NB: the December average is significantly different because note that we were away for much of the second half of the month, and had the HRV set on its lowest setting and the thermostat at around 13ºC.
Anthony’s report doesn’t just cover what actually happened over winter, it also uses PHPP (Passive House software) modelling to estimate what would happen in the rest of the year. Of particular note is that the model predicts mechanical cooling will be necessary in July and August.
The HRV certainly does not function effectively as a cooling system so far as we can tell. But I’m yet to be convinced by the need for mechanical cooling. Although the primary rationale for the orientation of the house and the window size and placement was Fall-Winter-Spring heating, the house was also designed to take advantage of the prevailing wind direction and for both effective stack and cross-ventilation. Simply by opening the windows (and turning off the HRV), we think we will be able to create significant cooling. Indeed that’s how things are working now (late June) even though we are only opening the windows on the tilt setting to minimize the chances of insect entry until we have had the screens manufactured (very soon). So I think we might be able to manage without any mechanical cooling. The PHPP calculations done by Malcolm Isaacs prior to the building had said the same thing – his solution was to have a large fan which we could place temporarily at one of the attic windows in summer, and use occasionally to do an almost full-house air replacement. This may be as far as we go…
There is a lot more in the report, but overall, Anthony characterizes our project as a successful one, and having been here, we know he like the place!
We are really grateful to Anthony for carrying out this research, as we never would have had such a detailed understanding of the house without it.