I had a little frost on the walls today in my coop as well.. and it's ventilated well. I opened the door for 10 minutes or so. It was toasty warm in there.. so I cooled it down a bit. Not sure WHEN my chickens will go back outside... they are afraid of the snow!
I videoed my rooster walking...
I haven't been out yet.. but so far so good.
Sounds like you need more ventilation in the coop.
Mine has quite a bit of ventilation and it was warm last night, but not moist. And mine is not insulated either.