I have the south side the most open with some good, large ventilation on the north side as well. East and west sides are closed off with plastic and tarp with some small ventilation at the bottom on the plastic side but nothing on the tarp side. We rarely get winds from the south or the north in the winter months, mostly westerly or easterly winds here on the ridge on which we live, with the ridge itself running north to south. In this way, most of the winds are blocked in my coop but with good air flow still from the end portions of the coop...which pretty much explains ventilation vs. drafts in a coop. I can stand in that open ended coop on a very cold and windy day and it feels several degrees warmer in the coop with not a whisper of a breeze blowing actively through the coop itself. Just a good, passive air exchange that keeps everything fresh while still staying warm.