Omg, if you are in Canada you should have bought a coop heater before you even bought a coop! But I've read an article from a guy in Alaska that provides no heat and they all survive. They are amazing creatures and can survive lots of things that we can't. Although on a certain level I don't really want them to be TOO uncomfortable, as my chickens are a part of my family.
But still, Canada is really really cold. You should get some heat! I should add that my heat pad can be setup in different ways and I have it standing up as a panel. I'll post a link to it, it only costs about 50 bucks and doesn't use much electricity. There is a 40 watt setting and a 200 watt setting, so on low it uses less than a regular light bulb.
Here is a link to the same heater I have which you can order online:
https://www.tractorsupply.com/tsc/product/producers-pride-brooder-and-coop-heater