I would love you to go to this page. I purchased this Eglu Cube chicken coop. Read the part on this page talking about raising chickens in Canada. I am not suggesting you buy a coop just use the info about double wall/insulating space and apply to your set up. Killer tomato is suggesting the same thing double walls with insulation but you must have ventilation.
good luck!
https://fourlegsorwings.com/products/eglu-cube-chicken-coop
good luck!
https://fourlegsorwings.com/products/eglu-cube-chicken-coop