If the ventilation is above their heads when they are roosting, you want need to block the wind at all.We did build it under a huge oak we have and there is plenty of ventilation as well. We built a club house on the back that is only 3' deep and 8' wide. They all get in there comfortably. We are able to block the breeze from the north side with a tarp if needed. I honestly don't know at which temperature I will need to do that.
