Hello from Massachusetts! I have a mixed flock of 5 hens ~ 1.5 years old. They have done wonderfully in an uninsulated/unheated coop through last years horrible, snowy, cold winter, and have been fine this year so far. Unfortunately two of my hens began their molt quite late, and are still regrowing their feathers. We have been below freezing a few times, but this week we are expected to get well below 0, even down to -10F at night with a high of 15F for 3 days straight. Normally I would just make sure they had full crops, close the pop door and be confident that they are hardier than I think, but am concerned about the late molters (and one is a teeny tiny bantum). They aren't naked, but they are definitely not fully feathered. I have an unheated basement (~55F) that I could potentially bring them into for the super cold nights (my husband would have an absolute fit but I don't care!). I also have their Brinsea Ecoglow from when they were chicks - I could put this in the coop and plug it in. Not sure how much benefit this would have. What do you experienced chicken keepers think?