I live in Alaska, much of my winter is around between 20F and -10F (or so) with occasional dips to -35F. I have just completed construction on our barn that will be the new chicken coop and need to decide how much ventilation to add. We have a very dry climate, our outdoor winter humidity is 30% - 50% based on my incubator's hygrometers left on the shelf over the winter. The new coop is 20' X 40', insulated cement slab, with foam insulation in the walls and ceiling and a single pitch room (so the snow slides off away from all the doors.) The ceiling is built using 12" joists The builder used plywood to sheet the interior ceiling, then blew 3" of foam insulation onto that and then put the roof sheeting on, leaving approximately 9" of air gap between the insulation and the roof. The eves were enclosed with screened vents on both the high and low sides... Our plan is to cut through the ceiling and the foam but not the outer "roof" layer. Our thinking is that the outside lower vents will let cool air into the channel, the outside upper vents will be where the warm air will escape. We were planning on putting the interior ceiling vents both on the low and high sections of the joist channels. The vents in the lower portion of the ceiling will let the fresh air into the coop while the higher ceiling vents will let the warm moist air escape. At least that is our hope... So now, my question is... how many inches of ventilation will I need? I am thinking of using the vent covers that I have seen inside of homes for air returns that are sometimes like 6 or 8" by 18 or 24" (I'm just guessing - we are going to the hardware store to look at options) Ok guys and gals... Your opinion matters. I can't wait to hear from you.