Hello, we have a 4x8 sheet of plywood as the floor with cement blocks to keep critters from digging under it, also to keep hens from laying under it.
Then the walls are about 6' in the front, 5' in the back. It was built in a existing shed, tar paper on the back side to help stop breeze. I use the deep litter method, it has an "in law" appt if someone is ill or needs time out, and this holds 5 hens in a Maine winter.
I do not insulate, yet I do use cardboard on the ceiling to help insulate from the cold that likes to drop down.
The outside wall you see is made of wire with heavy clear plastic over it so the girls have a tad bit more room on sunny days- or inclement too.
This winter I allowed the girls free access to outside except on bitter cold days, and they were very healthy and they do have CRD that needs air that is drier then a wet environment with heated water and manure.
Then we have a hutch that holds 4 bantam Cochin's. The Living quarter is styrofoam insulated double walls.
The "run" has hardware cloth but we put heavy clear plastic over it and it was plenty warm for them, I did use a heated water bowl.
I am pretty impressed by the coops that members have on here. I'm proud of ours, but that is sentimental cause DH made 'em!