So what I've been told is that heating your coop is kind of a double edge sword so to speak. If you heat it, they don't grow as many feathers, and then if the power goes out you have chilled chickens. I am in Canada (southern Ontario) so we get pretty cold up here. I have 3 sex links. Their coop is insulated but no heat. I also have coworker that has 6 and she doesn't heat her coop. I think its totally up to you how you want to handle it. Maybe something like a heated perch is a good compromise and adding insulation to your coop so their heat stays in more. Lots of shavings on the coop floor for insulation too. And I'd keep them inside for the full 6 weeks. Good luck!!
Is it true they will not grow as many feathers? I had 3 Rhode Island Reds till they were stolen for years with a Cozy Coop Heater and they did not seem to have problems being outside in the cold even when it was a bitter cold. If it snowed I shoveled an area for them so the could come out without trying to get thru the snow and everything seemed okay and I never had a sick hen. I do not fill the coop with hay or anything else like it, I always had newspapers on the floor that I could pick up each day and place fresh papers because I felt it was cleaner. The idea of hay and other materials that could be moved around and not removed was something I did not want for my girls. My girls still were laying eggs like crazy all year long and age did not really slow down their egg laying.
Everyday they got fresh water and winter it was heated so they could get a drink no matter how cold it was outside.