Our coop is 8x8x8 and houses 5 New Hampshire hens and 2 White Rocks (for now!). The door and window are on the south side; the nest boxes are mounted on the east interior wall. The north and south walls stop short of the roof by about 6 for ventilation (that is, the studs go all the way, but not the sheeting). Its cobwebby up there, but Ive never had ammonia buildup. My Q is this: how many of the 6x16 spaces can we safely close for the winter? I noticed last night that the cobwebs had frost on them from heat/moisture rising from the girls. They obviously need ventilation, but I want to conserve heat wherever possible. A clear, windy night here can be -10deg. /-50 wind chill. Also, what should I feed them while grass is hard to find?