I built a coop that looks like a big dog house, except it has a sealed "person door" on the end and a pop hole that has an alcove and automatic door. It has a "picture window" that's made out of the frame/glass of an old picture. I insulated the interior with 1/2" foam board covered with hardboard. I heat the coop to 45 degrees F. with an electric space heater controlled by an industrial controller I got for free. So far, my four chickens love it! It got down below zero for a few days and they tolerated confinement very well. I use pine shavings for litter and vacuum out the house about every two weeks. On warmer days they free-range all day on my 1/3 acre and roost/lay in the chicken house. When it's snowy, I lay down a board for a "pecking patio." I have it lit up with a timer for two hours every night after dark and they have continued to lay very well. The chickens are Australorps and an Orpington and those do well in winter if kept dry. As you can see, they are very fluffy and well-insulated breeds!