Nice coop! I have the same exact one except my doors open sideways
I live in Southern MI and it gets too cold for me here so I figured if I was gonna enjoy my chickens, I wanted to be sure they were warm too. I put in a red heat lamp on a thermostat to keep the temp inside above 35 degrees. I haven't had any issues and have 6 chickens in the coop (bantams and standards). They have the option to stand by it or stay farther away.
