Heat no, you will not need it if you have insulation, believe me I was also worried, I' spoil my girls and also wanted to heat, but when I went out at night, my girls were fine. I have a vent cap on top of my coop, that's the only ventilation I have eve used. I have windows on three sides but I do not open them during winter time. I have never had a problem with humidity in the coop, why ? Because I clean all the poopy shavings every two weeks and my coop stays dry. I use shavings, so poop drys fast and diatomaceous earth in it. I also have a pen that is totally covered roof and sides get totally covered to keep wind out. There are pictures some where on here I posted . With my covered run, the birds do not have the bitter cold blowing into the coop through the pop door. The pen is dry, and covered from snow and wind and I think this has a lot to do with warmth for my girls. I have 4 inches of insulation between my coop walls, and use a tin can heater for the water. I also have stated I carpet my roosts. ( 2x4s) so there feet are not on a cold piece of wood, this has helped them sit on there feet and them be totally sitting on the 4 inch flat side . They went out every day into the pen, some liked to just look out the window and some spent the day out side. With the covered pen it makes for a more comfortable winter for my chickens. Granted some people have to big a pen to do this, but at 12x17 pen, I can do so easily. I heard around here some where opening a window for ventilation was not good, it allowed cold in instead of ventilating. my coop has electricity but I do not plan to heat my coop, unless it goes down to pretty low and last year when it hit 28 below my girls were warm and fine. Seriously I went out constantly during the nights and they were all huddled together and warm. Even there feet which was tucked up and under them on the nice carpeted roost. I used a very low low pile carpet .