This is our first winter, learning as we go. We currently have 21 pullets, 3 roos in a 10x12 coop with 10x24 run. We were free-ranging, but have been keeping them in coop to train them to use nesting boxes. They are all just starting to lay eggs (girls at least ). Not sure how long they will be kept in coop since neighbor's puppies learned chickens taste good (we are trying to work on that issue separately). We have put in 2 roof ventilation thingees, and 4 ventilation rectangles in front and back walls. It all seemed to be working through the coldest weather recently, but now its hard for me to breathe in there. Yesterday I stirred up the litter, added what I had about 1/2 bag of Stall Dry.This morning, DH hung a box fan to get air moving more. We let chickens out yesterday, but nearly lost two to the puppies. What do I start working on first? Do we need to change out the litter? Do we need more ventilation? Are there just too many birds in the coop? The birds are staying in the coop because the run is muddy. I can't think of anything else I can add. I just need some suggestions! thanks in advance!