I decided that instead of building a second coop that I would use the space (4'x5' and 3' tall) to create a second coop. I've got it all figured out except the ventilation. In the current coop I've got open eaves, two Windows that at 6" tall and run the length of the coop with adjustable shutters and two large openings that get screen in the warm months and wood in the cold months. Do you think long windows with shutters will be sufficient during the winter without open eaves? My general rule of thumb is open shutters over 32°f and closed if it's colder. The bottom coop would have no secondary ventilation in the winter.