Our projects
the greenhouses, 'Serres PASSIFLORE'
Jan. 2021: After 3 years of awaiting, our first passive solar greenhouse (part one of two) is under construction! (Part two requires more investment and will be delayed a little. For now we start with the West Side, and both sides are attached to the same building.)
The passive solar greenhouse was still a little known type of building in Quebec, even though recent interest arose after some students and homeowners' projects were documented on tv. In fact, this one does not look like a regular greenhouse for it has an insulated roof.
Our system is based on the information given by SolutionEra during an ecological building class in 2014 held in Chertsey (QC).
It is more or less experimental as it comprises two sides (instead of one entirely oriented towards the South or SSE as most passive solar buildings normally are). We will be monitoring air movement, passive condensation control and temperatures in the coming years.
We hope this first greenhouse project will give us a better idea how to build the next one!
Below: installing an 'old' reused window - still good for another use!
The Greenhouse
View from Inside The Greenhouse (photo: 2023)
Summer, 2024:
Adding thermal mass
Please note it’s a quick line drawing with some colour added, scale and proportions are not accurate, there are more windows to the outside and way more block pillars underneath the wood floor - it’s simply meant to give a general idea. Light grey arrows show air movement when ventilation is turned on. Dotted line arrows (vertical) show cross section from which the image on the left is taken.
A - Greenhouse/Growing area
B - House/indoors
C - Ground, earthen
February, 2025
As I write a paragraph for our first 2025 newsletter, we’re in late February, and the improvement I added to our small attached ‘greenhouse’ seems to work better than expected! I really got enthusiastic when I saw how well it has done so far and to what extent it could open up possibilities! In short, it was an ordinary solarium with an insulated roof and windows oriented south/southwest to get full winter sun from late morning to sunset. Last year, its floor was earthen and without much else its temperature sometimes dropped to minus 15 C (5 F) in winter. I took a few days off the garden last summer to build a semi passive thermal accumulator (very simple thermal mass) and see how it would do. Semi passive? Because it releases accumulated heat at night and gets ‘charged’ when the sun shines, helped by a cheap good old fan placed strategically. ‘Luckily’, we got to test it this winter because there has been many more cold and grey days this winter. Even in this scenario, it never dropped below minus 5 C (23 F) !
The fan is turned on and off by hand, no fancy technological stuff (one may want to add an automatic on/off switch -mechanical or automated - when temperatures rise high enough while one’s not there to turn on the fan). So the warm air accumulated in the upper part (grow area) gets pushed underneath and goes through the thermal mass.
We had a large pile of concrete blocks and tiles standing in the backyard since we modified the landscaping around the house (adding gardens and removing concrete items) so in there they went! (see plan above and photos below).
Blocks were piled in three layers and spaces were left in-between the pillars so as to increase surface area. On top of the blocks I placed a layer of 18 inch wide square concrete tiles, topped by a layer of plywood. (In fact I wondered if that would be enough of a thermal mass. Even though I had calculated the volume necessary for a theoretical greenhouse about this size, I did not take the time to evaluate how much actual mass I had brought inside. I used up what was available here and it was three blocks high so as to leave enough space « upstairs » in the grow area to move ‘freely’ or nearly so and have enough grow shelves.) Lights are now installed on the shelves on the wall side and are ready for a new season!
Insallation of the concrete blocks (summer, 2024) underneath a floor (to be installed)
Cooled air passed through the concrete block area below floor
Warm air pushed through the concrete block area (thermal mass)
Photo taken from the fan's location
Results!
While we had, from October, 2024 to Feb. 2025, a similar winter in terms of general temperatures (although the thermometer registered a few more very cold days), it was cloudy. (We used up more wood to heat the house). In December and January, the greenhouse thermometer was generally indicating around 0-4 C (32-39 F) and doubled as a giant refrigerator for my prepared food. Not bad. Those sunny days when I was able to start the fan (warm enough in the greenhouse) were fewer until, say, early-mid February. And outside night temperatures dropped more often this year with about 4 events of minus 27 C to minus 30 C (-16 to -22 F). You probably guessed I love to pile up some kind of weather data… While I got a few lows of minus 15 C (5 F) in the greenhouse the year BEFORE I installed the thermal mass , the lowest mark in the greenhouse this winter until now was minus 5 C (23 F) !! Passive / semi passive solar « technology » is indeed impressive.
The sun’s heat, then the heat losses that come from the house through two (closed) double glass windows and of course the heat accumulated in the ground plus thermal mass below are the only energy sources and storage that keep the greenhouse air much warmer that the outside air. And what’s more, when we get very sunny afternoons, I sometimes open a window to let in the hot greenhouse air (it’s dry air in winter) and warm the house for free! And it’s a pretty nice place to be. Snow on the ground, clear sky and a warm and sunny place that feels like springtime.
It has been a few years now I plan to build a second greenhouse, not attached to the house, and this motivating experience brought to my mind some more design ideas. One farm building project at a time. Meanwhile many planting, growing, homesteading tasks and breeding/selection projects unfold - that’s why so many things seem to move at a snail’s pace here. Yet it allows me to dig deeper in the subject, to plan better - instead of doing it too fast: in certain cases like ours, it’s a good thing to NOT have access to Ag subsidies (when what you do is just too weird for the government's agricultural help subsidies spreadsheets to function - just kidding). But someday things get done and we learn - that’s the important point, right? Second important point? To show some of our projects so as to inspire more people in building their very own form of local resilience initiatives!
