Ok, I've decided to build a small, winter coop for my five serama hybrids. I live in North Texas where we rarely get freezing weather, but we do get stretches of winter weather that dips into the upper 30's at night. This coop would be used only during winter. I'm going to roof my little 4' by 4' coop with clear polycarbonate panels, and put it in a sunny location, so that the sun will heat it up during the day. The chickens will be out in their run during the daytime, so I'm not worried about it getting too hot in there for them during daylight hours. I'm hoping, though, that the retained heat from the sun will help keep them warmer during the nights. My question is about where to put the ventilation vents for this coop. Traditionally, the vents would go on the tops of the walls, but it seems to me that this would just defeat the purpose of the "greenhouse effect" -- the warm air would just vent out of the coop. So I'm thinking of putting the vents down below the level of the roost. That way, it would be the colder air that vents. Does anyone see a problem with this? Would that create a draft within the coop, even without any high vents in the coop?