I have a really secure run and so often keep my pop door open so chicks can go in & out in the AM/PM as they please. When winter comes, is a 12" pop door going to be too drafty for the chicks (it is floor-level) when temps get to freezing? How cold can the coop get? I'm hoping to always keep the pop door open but maybe that's too cold. Should I add some doggie door material to it perhaps to keep out drafts but still allow for chicken convenience? I have a few other vents here & there & two large windows (which will probably stay shut once it's winter). I'm having a hard time figuring out the "no draft" rule combined with the "adequate ventilation" rule combined with "don't freeze the chickens" rule.