NTBugtraq you are so right. I went through so many posts before it got cold (as i'm a first time chicken rancher), and was so worried about how my flock would do in the cold. But buying winter hardy breeds from nearby I've realized the best thing i can do is not baby them. I do have a heat lamp in the coop, for -20C to -30C nights but otherwise they have been absolutely fine in the cold.
You (The chickens really) don't need the heatlamp, even at those temps. They do not need it.