Ventilation is for two reasons, ammonia and humidity. If you get rid of those through alternate means, you can shut the door.I had found oil radiators on Amazon and still have a Cozy coop heater and 2 pet heating pads. DH let me use it the previous year with the Eglu Cube. Then last year we got a large coop and paid extra for insulation so I couldn’t convince him to pay a higher heating bill.Most died when it got to -10 C and we forgot to close the little doggy door that leads to their run. Also read about needing extra ventilation in the winter so we weren’t overly worried about it. 2 frizzled serama survived but were weak so I brought them inside and even changing their bedding often they were just too smelly and my cats wouldn’t leave them alone. When the weather got better brought them back out and found Camille’s body in a rat hole. Rehomed Pinecone before she would die too. Probably won’t get any more bantams until I move back to California many years from now but at least with the standards they come sexed because we are only allowed 5 hens in the city.
A 5-gallon nipple bucket is in our coop, but if he won't heat, there are electric nipple waterers, so there is no open water.
We use horse bedding pellets which dries the poop up and the chickens pulverize it by walking on it. We put stall refresher on top of the nest boxes where they roost and the walkway in front of those.
Our coop at this moment is 45% and outside it's 58%. We have no ventilation other than an exhaust fan, when it runs. I am not suggesting not to ventilate, only that there are alternatives to cut down what's needed.