My experimental winter greenhouse

Alright, before winter I had open a post about bioshelters. I am very interested in mixing a greenhouse with a chicken coop or with rabbits and/or fishes (there's a little more to it but in very brief, that's a bioshelter).

https://www.backyardchickens.com/t/930289/anyone-in-cold-climate-using-bioshelters

As this is fairly new, not used often in our cold climate and since I didn't find a lot of information, my first step was to wonder: is a winter greenhouse realistic in Quebec, with our cold winters?

So, I built a little greenhouse to make a test! It is very simple.. think of a rectangle.
The front is a window. The top is a window. The back is a plastic tarp.
Both sides are cement blocks. I've piled compost (mostly wood shavings, to get a lower N ratio so it would compost slowly over winter) on both sides of the greenhouse. I thought this would block the small cracks where wind would come through and also maybe give a bit of heat to the greenhouse.

Came autumn, I moved a few cold-loving plants in the greenhouse.
They lived to about mid-december.
I noticed that until -10C they were fine, no sign of problem or distress since the greenhouse would heat around 20 degrees (average) during the day and remain around 0, -3 at night.

When we reached -15C, things started to die. I think if the temperature would have gone back up, they would have survived - because the plants died slowly, on the course of a few days. The day length and also the snow falls where causing problem here (snow covered the window, thus the daytime highs where not as high as they could be).


Anyway!! This gave me an indication that -10C was the key temperature.

I made some research and checked my local weather for the last 3-4 years to get an average of the date where we would reach -10 without going below it. It gave me March 5th.

On march 5th I took my shovel and removed the snow around the greenhouse. The last 2 weeks had been -30C and crazy cold.
That day was -17C... and here is what I found:








Perfectly thawed soil!!! Even though the snow blocked the windows for all winter. I was amazed, surprised, happy. I was surely one of the few Quebecer with hands in the garden dirt at that temperature

So, I let the sun warm up the greenhouse for about a week. I have a trench in the middle of the greenhouse for compost, so I removed last year's compost and added new one, in hope to get some heat form it. I added a plastic tarp on the soil to keep the warmth in.

And on march 8th I planted 3 cold-hardy plants . Kale, mizuna and claytonia. I put a second layer of greenhouse on those (just some plastic bags or glass pots). I put a thermometer directly in the greenhouse and another one inside the second layer (not sure I explain well).

For the last 4 days, the max highs where 38C. The lows were -5 (it was down to -14C outside last night).

So here are some images of last night:










Overall, I am very happy about it!


Stuff I did wrong / learned:

- The orientation of the greenhouse is not 100% correct as I had not considered the sun being lower in winter.

Hum, I thought there was 2 other things in that section but I forget for now ;( I'll update later if I remember.

For sure, I learned that it was possible, manageable, fun and simple 100% worth it.