I have built my run and am now in the process of trying to provide more ventilation in my coop. I realize that it will be impossible to provide the total amount needed. I have 45 birds. I am working with an existing 8’ x 14’ gambrel structure about 10’ high at the peak. I want to open the ends above the doors and am thinking about installing large return air grilles. My concern is that my birds roost in the rafters and I don’t want there to be a draft. I will also put air grilles that can be opened or closed above each window. I am hoping that now with a secure run I will be able to open the back door until it gets below freezing. I could really use some input, ideas, thoughts?