Polar Vortex vs. The Thomas House

Well, we’re almost through the “Polar Vortex” of 2019, aka, finally some winter weather in Canada! We’ve really been lucky this year with mild temperatures until early February hit. We have officially rode out our first winter cold snap in our furnace-free, solar powered, net-zero energy, “damn near” passive house. And the results? Pleasantly surprising!

I’ll be honest, even though we preach high-performance homes and have definitely drank the passive house koolaid, actually living the experience provides valuable insight into the differences between practice and theory. But, thankfully in this case, they merged with positive results and some surprising observations.

The front door - next summer’s landscaping project!

Normal winter conditions in Central Alberta have an average temperature that ranges between -2° to -16° celsius. During these regular days, our home maintained a very comfortable living temperature, with its own fluctuations. The high levels of insulation, with limited heat loss through air leakage, and passive solar heat gains all contributed to the minimal temperature fluctuations in the home. However, it’s not a perfect system, and therefore, additional heat was required in order to “top up” the heat, especially at night.

We relied on a small radiant electric heater in the basement, where there is. minimal solar heat gain, which provided enough cushion for the main floor to maintain a regular temperature for most of the day. Almost every night we slept with our electric wall radiant heater on in the bedroom only, in order to ensure we have a steady temperature for ourselves and our baby. In the daytime, and on sunny days, we were able to maximize passive solar heat gain through our triple pane, low-e, argon-filled south facing windows. These windows were designed in order to allow solar heat to pass through and are much more energy efficient than your standard triple pane window available. Keep in mind, you can install “triple-pane low e argon filled” windows, but there is a spread within this category of windows that ranges from poor performing to high performing! On certain milder days with the sun full on out, our upstairs could reach 23° celsius with solar heat gains alone.

Now, during these extreme cold snaps, we’ve had to modify our behaviour and function in a slightly different manner. This week, temperatures have dipped to -37° celsius overnight, which doesn’t factor in windchill (luckily we are sheltered by trees & hills which is helpful). We ensure that we have an extra heater turned on in the basement, just in case. Every morning and throughout the day we’ve been firing up the Morso wood stove until the early afternoon when the solar heat gain maximizes (unless it’s cloudy), and then fire it up again in the evening. We’ve only ran the wood stove constantly one day only through this period. Alternatively, if it were to be as cold as the day we ran the stove constantly, but were not at home, we would have ran a heater in the main living room in addition to the two in the basement just to maintain the temperature, but for now it was not necessary. We had actually cut an incredible amount of wood this summer in preparation for this winter (with some wood prepped from the 2017 season). We were a bit worried as it wasn’t seasoned long enough but with the time constraints between working and building the home, we didn’t get a chance to focus on wood collection until late in the summer. Luckily, we haven’t even touched 2018’s wood pile and still have plenty of wood to burn. If we’re lucky, we won’t have to touch last year’s wood at all.

Now that we’ve faced the some of the lowest winter temperatures that Alberta can throw at us, there’s definitely some interesting observations and some lessons learned. Especially in the comfort department.

First, design and pre-planning is crucial!!! I can’t stress this enough as there are certain features of the Thomas House that could have used a bit of tweaking, if we had the foresight in identifying potential issues. One particular cool location in the house is in the kitchen, above the HRV ducting to the outside. I didn’t even notice this cool spot until this week’s low temperatures, so it’s definitely only an issue for maybe 5% of the year. Although the ducting itself is insulated, I think that we need to add in some additional insulation between the ducts and the floor joist aka the mechanical room ceiling. There is some definite heat loss happening in this area despite having 7 inches of spray foam in the rim joist and surrounding the ducting in these locations with an additional R14 batt stuffed in (leftovers we didn’t want to waste).

Luna enjoying the heat from our wood stove

Standing in front of the ground-mount “off-grid” portion of our solar system. You can see the wood stored underneath, as the panels provide a dual purpose!

Another location of heat loss was our passive house “cat door”. We’re definitely getting frost there but I can probably attribute that more to the damage incurred by our cats trying to escape when it’s closed, leaving the seal broken. One last oversight was not running an additional dedicated outlet for our bedroom electric heater. Running two heaters upstairs trips the breaker and we originally did not intend on installing two upstairs but we wanted the flexibility of choosing electric over the wood stove for convenience. Regardless, we don’t need heat in both the upstairs master and the upstairs living area at the same time as each room receives passive solar heat gains at different times and we are not usually using both rooms at once. A small footprint also allows heat to circulate efficiently throughout the floor.

As for the solar production, it’s no secret that wintertime in Alberta produces very little solar energy. Our lowest month was December, with only 153 kWh being generated at a credit of just over $20.00 to our energy bill. Alternatively, our consumption was 1733 kWh’s for the same month. Luckily, our solar energy production has been calculated carefully so that we produce as much energy as we consume annually (net zero energy) and therefore will make gains in the summer when solar energy is at its peak.

Comparatively, if we were living in a new, “code standard home”, we would have consumed 62% more energy to heat and power it. So, even though solar production isn’t at it’s peak, the efficiency and performance of the Thomas House speaks for itself.

Before we moved in, I’m not going to lie, I had some concerns about comfort. I knew that building a home like this technically should be warm and cozy, at the very least, livable. But there was a little voice in the back of my mind worrying that we were not doing “enough” to ensure we would have enough heat during the winter, and that we weren’t secure enough in our access to a “reliable” energy like natural gas for heat. Having a newborn to take care of exasperated that fear. But, we’re not just surviving in a house that uses extremely little energy, were thriving. And secure. And cozy. And happy…