Our winter temps can get down to around -5C (around 20-23F)
These are really quite moderate temperatures. The main thing will be to provide water that isn't frozen. There are many kinds of heated waterer available but I can't recommend anything because I'm in the US southeast where just bringing my waterers in at night is sufficient.
Don't be tempted to close up so much that you compromise ventilation. A generous flow of fresh air is just as important in the winter as in the summer.
Insulation Foam Board.
Chickens are notorious for eating foam board. If it's installed where they can access it they will peck it to pieces and eat the bits.