Here's what we did, and my guys are still babies so it hasn't exactly been tested yet - but in theory it should work lol
The inside of the coop is plywood, and it is insulated then we have bead board on the outside, red tin roof. The coop is 12x8 and 8 feet tall, with vaulted ceiling inside. 2 human doors, 3 windows, 1 "pullet-shut" chicken door on a photo sensor and solar power.
My husband, being in all trades in construction and a painter, decided to use the same stuff on the inside and outside of the coop, that we used to seal the logs on our house. Its some high grade professional stuff, that I would compare to some form of deck sealer/ water repellent. It looks really nice, and we can literally hose out the coop when needed. Also, under the roosts, we cut a "trap door" that falls open when unlatched (the coop is off the ground on one side by about 4 feet, unlevel ground lol) and I can park a wheelbarrow right there, shovel the poop and bedding right thru that trap door then hose the whole she-bang out.