Just a suggestion here...if you do cut some vents in your coop, put them up high on the wall, not down low or under your roost. Chickens can stand some really cold weather, but drafts are killer! You do not want cold air blowing on them from vents placed next to or under their roosts! If the vents are up high the ammonia smell from the poop will rise up and out, also the moisture laden air from their breath, but any wind will not blow directly on them. Ventilation is extremely important to have healthy chickens.