Outside of adding insulation under the roof, to help with summer heat, insulation, in a coop is USELESS. Waste of time, effort, and money. What good does insulation do, if you have the coop open to the outside for fresh air/ventilation? Answer, absolutely none. Because as we all know, the coop HAS to be open, and ventilated, even through the coldest winter days. It kinda cracks me up, to read about people saying, that their coop is 10-15 degrees warmer inside, than the outside temp is, because they have insulation. I have a Wood's coop, the whole front wall is wide open, year round. There is not one piece of foam, not one batt, no insulation at all. Except what the chickens are already wearing. And guess what, during the winter the coop is 10-15 degrees warmer inside. Sometimes, higher than that. I actually have to crack open the upper monitor vent windows, for more fresh air. The birds themselves generate the warmth. I read somewhere, that each bird, is like a 10W lightbulb in the coop. All of them giving off warmth.
Put insulation in the walls, then add some interior walls, and you are setting up a perfect habitat for rodents, insects pest, and who knows what else, to set up shop. A coop is not like your house. You usually don't have your doors open, and food laying around on the ground/floor. (Some houses do, but that's another story, and they'll have a rat problem too) It's enough of a job to keep things relatively clean and orderly in a coop. Don't make the job more difficult, by giving the pests a nice hidden place to live, in the coop. I see people say on here... "Well, I have insulation, and I don't have any mice or rats." You don't know what you have going on in the coop with 100% certainty, because you can't see through walls. When it's noticeable, you have a BIG problem. The pests have already established themselves. Your chickens will have noticed the problem, long before you. But, sadly, they can't tell you.
And if I have first yr pullets in the coop, guess what, I get eggs through the winter too.