Image Credit: David Murakami Wood This table compares the R-values of components of the Wolfe Island Passive House to those of a hypothetical house built under the 2017 Ontario building code. (The first number is the metric R-value, with the imperial R-value following in parentheses.) The bar graph compares heat loss through various building components of the Wolfe Island Passive House to the heat losses in a house built to the newest Ontario building code. Annual energy consumption for heating and cooling at the Wolfe Island Passive House compared to a code-compliant house. Annual energy consumption by device at Wolfe Island Passive compared to a built-to-code house. Estimated annual electricity cost at Wolfe Island compared to a code-compliant house. Average indoor temperatures (in degreees Celsius) on the first and second floor. Note: The December average is significantly different because 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 (55ºF). Modeling shows the predicted mechanical cooling that would be needed in July and August, but if we take advantage of prevailing winds and open the windows, air conditioning may be unnecessary.
Editor’s note: David and Kayo Murakami Wood are building what they hope will be Ontario’s first certified Passive House on Wolfe Island, the largest of the Thousand Islands on the St. Lawrence River. They are documenting their work at their blog, Wolfe Island Passive House. For a list of earlier posts in this series, see the sidebar below.
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 than ours. But, with Anthony’s permission, I will just highlight some parts of the report as it relates to this house.
Anthony, a Certified Passive House Designer, compares our house to the new, highest Canadian code standards. Bear this in mind, because the average Canadian (or U.S.) 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 (see Image #2, below). The whole assembly (including the cross-laminated timber, which has an R-value of between 4 and 5 on its own, and siding) would be nearer R-50 in my view. But conservative estimates are better than exaggerated claims for testing efficiency. This leads to some estimates for heat loss, which are summarized in image #3 below.
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 (see Image #4, below).
Plug loads will probably be less than estimated
When it comes to plug loads, I think here there is a little more erring on the side of conservatism here (see Image #5 below). Anthony basically has estimated the energy consumption of our appliances and lights to be the same as in a standard house meeting the 2017 code. 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. Plus, 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 (see Image #6, below). Of course, one of the problems with bills is that you can only reduce them so far. The majority of our electricity bill is not the charge for kWh used, but the fixed fees and delivery charges, over which we have no control, unless and until we are totally off-grid, which brings us to: greenhouse gas emissions.
On the emissions issue (see Image #7, below), I would imagine that once we’ve installed the solar thermal and PV panels (probably this summer, although the timing depends on costs), and possibly some other wind-based generation, this will further reduce our electrical draw from the grid and our monthly costs, and therefore also our greenhouse gas emissions. Our eventual aim is to have zero energy bills and net-zero GHG emissions.
Winter and summer performance
You can see more detail about winter temperature and humidity in the preliminary results we posted earlier. While (as Anthony notes) we found the house perfectly comfortable over the winter (see Image #8), I think that 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. We shall see!
Anthony’s report doesn’t just cover what actually happened over winter, it also uses PHPP (Passive House Planning Package) modeling 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 (see Image #9 below).
The HRV certainly does not function effectively as a cooling system, so far as we can tell. But I’m yet to be convinced of 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 also was designed to take advantage of prevailing winds and 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 since he visited, we know he likes 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.
David is currently at work on a final column that will sum up his experiences on the project. GBA will post that as soon as it becomes available.