Your coop includes the roofed run area? You have good ventilation there, not in the enclosed building. That small upper window, at roost level, could be partially covered, with an inch or two left open on the top. If the birds will be below that level when roosting. Otherwise, where's the upper ventilation?
And are the openings where the metal roof ridges are covered with hardware cloth? If those openings go into the coop, it's a tiny amount of ventilation, but too large to keep out rodents or weasels.
Your roofed run will be great all winter, with sheet vinyl covering at least the windward sides. Leave the upper foot or so open for ventilation. Very little snow or rain will blow in on the leeward sides.
Chickens hate snow, and you won't want to be shoveling it out very often.
With those walls closed in with clear plastic sheeting, the lower doors to the closed coop section can be open all the time, much nicer for everyone, as long as it's all predator proof.
Mary
