My 4'X8' coop has five vents high up on three walls each about 6" tall and ranging from 12" to 36" long. I've designed them with hinged flaps that can cover some or all of them, some or all of the way. As it has gotten colder at night (down into the 40s), I've closed the two that are on the end of the coop with the high roost so there isn't a breeze blowing across them at night but left the other ones open. Can I close them up on particularly cold nights this winder or do I truly need to allow for ventilation 24 hours a day? I'm sure you old timers get crazy with being asked the same things over an over, but while our really cold spells don't usually last more than a week or so, it can get down to -20 or even -30 during January or February here in Colorado. By the way, I have 8, 3-month old pullets. All cold hearty breeds.