I live on the Kenai Peninsula in Alaska (about 160 miles from Anchorage). I was gone for 4 days, and found out it was 14 below zero (farenheit) for a couple of nights, and the heat lamp had gone out. I use a 75-100 watt red flood light in the roost, on a timer that comes on from 7:30 p.m.. to 10:00 a.m. when temps drop to 10 above or less. I have 10 red & black sex links, a heavy breed. They were all fine, no frostbitten combs/waddles, very happy and laid well while I was gone (I had a neighbor pick up eggs, but she didn't know the flood lamp had burned out). I think they would survive to 30 below or lower if they had to.
We're back in business, and everyone's happy, but they didn't seem any worse for the wear. My coop is not insulated, but I have some hay bales stacked on the windward wall; their roost area is heated with the lamp, and has a droppings screen below, covered with chicken wire and straw. They have step ladders (2) to walk easily from the roost to the coop floor.
On warmer days, I go out and roll up the straw to clean up the poo, throw it away, and put down a new bed of straw. The coop door is open on all days above 15 degrees, and they step outside, eat snow, and generally seem comfortable. I've had chickens for 5 winters, even a Polish, and she did fine. I used to get a "used" flock in springtime and give them away in November every year, but I've learned how to keep them through the winter. It's easy.
I use a car block heater pad on a galvanized base for an 8-gallon galvanized waterer, which I fill up with 4 gallons of water at a time -- it lasts for about 4 days, and their combs don't stick to the side of the waterer because it doesn't freeze up as badly as the heater unit that comes with the tank when you first buy it. I keep a 40-watt bulb in the coop on a timer to give them 14 hours of daylight. I put a fresh bale of hay in the coop every other month, untie it, and let them spread it around (which they do, and they have fun). I feed them table leftovers conservatively, fresh greens, scratch once or twice a day, and provide unlimited access to 16% protein layer pellets, grit and oyster shell. I'm getting 5-10 eggs a day from 10 hens. I take them scratch (about 2 cups) in the morning, and again at about 4 or 5 p.m., before they roost, but sometimes I'm not home, and they are still fine. They eat a lot more right now, and are going through a 50 lb bag of pellets every 4 weeks.
I don't know if you can get the hens through Canada if you drive up here. Better check with the border patrol.