What is important in a coop,,,,, is VENTILATION. Poor ventilation leads to moisture in coop ,,, which leads to frostbite on extremities ,like comb, and wattles. Poor ventilation also contributes to ammonia buildup . (NO GOOD)
Proper ventilation, means air movement without a draft situation, that would ruffle chickens feathers.
Another factor to consider, is your breed of chickens. If you have cold hardy breeds, then you should be fine. If your chickens are not cold hardy, insulation would not be the answer regardless.
Hopefully your ventilation is proper. Vermont is known for some gusty winds. Try to provide/fashion wind breaks if you need them.
It is good to feed your chickens extra carbs during cold weather. Carbs do help chicken generate heat calories. I know there are flocks of people that will disagree, and debate me over that.

There are also equal amounts of people that agree with me.

I give scratch to chickens during winter. They don't lay eggs anyways. (I don't have production chickens, or leghorns AKA egg machines)
Besides good food, make sure they have plenty of liquid water. Snow is not a good choice as water source.
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
