I have a secured run attached to my henhouse, so leave the pop door open 24/7. There is also a vent near the ceiling of the henhouse, that can be shut. The henhouse is insulated, and very tight. Now that I have more experience with hens, I'm worried about adequate ventilation during the winter if I shut the vent and pop door, so I leave both open. There don't seem to be active drafts inside the henhouse, and the waterer is on a heating unit with a thermostat. Any input? Also, I'm considering installing further venting this spring after the weather changes. Any suggestions? I should ad there is a 3x4 thermopane window on a crank in the henhouse that I can open as well, but it cranks out from the bottom.