How's your greenhouse holding the heat? I found that having the heater on the floor and fans high that it holds the heat by several ºC. The fans make a huge difference. My GH is 8'X12" Costco kit. I have a infrared electric furnace with the little electric heater 3000BTU working off two different breakers. With -13ºC, I can keep the greenhouse above 10ºC. In past years I had lined the greenhouse with bubble wrap, but it is a lot of work and fairly pricey. The bubble wrap also changes the light conditions. This cold spell will not end too soon. Cold & sunny is ok, but these cold cloudy/snowy days suck.
-13ºC=8.6ºF and 10ºC=50ºF
