I dont have access to electricity for my coop. I let my 2 chickens free range in the day. Our winters will get in the 10-20s at night. I was planning on leaving my poop door open and closing the main vent to prevent a direct draft. I really dont want to add a heater to the coop (heat and pine shavings are risky). I was planning on adding a DC power for my water bowl heater or a solar system. I have a few battery packs to run my telescope. I have a fairly thick covering on the floor of pine shavings. Suggestions?