I hear you say--keep you coop only above freezing. Ok, I realize I am "down south" now, but we still get around -18 or so. Idon't have an insulated barn, and I don't heat it. I use an electric dog water bowl to keep the water from freezing, and occasionally--if it is really cold (like below- 15), i keep a heat lamp on. Also, if I am expecting it to be very cold, I throw out a few handfuls of corn--its; supposed to generate heat..
Deep litter, if done correctly will keep thngs warmer too. It will generate heat as it composts. I do this in the winter. If your barn is insulated R25 with a heat lamp, I'm sure that your birds will be just fine.
Where in the Yukon are you? I used to live Near Timmins, ON. Still south compared to you. The coldest we got was around -35 to -40 usually in February. I would still trade that for the winters down here any day!! (as you can tell from my username-- I miss the north)