We live in West Michigan, so it gets pretty cold. We don't insulate our coops, nor heat them. There are no vents in the enclosed part only a window we keep closed. There ARE small gaps in the slats which probably let air/drafts in. The big door gets opened to feed/water them, and there's a small "ramp" door opposite of that which leads to their fenced in run. Its always open. None of our feathered-in chickens ever died from the cold. We have had silkie bantams, mediteranean breeds, on up to fat ol' Orpingtons. We use deep litter method, and change it 2 or 3 times a year. They love scratching in it. Approx three times a year we sprinkle Trailer Fresh over particularly soiled areas. Do they get mites or lice? Dont know. We dont inspect them. They eat, drink, scratch, lay eggs, and keep their feathers (except when molting), so we're all happy!