Do you air out the stalls during the winter months?

In the day if it is not snowing or freezing rain, I open both doors and let it ventilate. At night I leave the doors cracked, and fortunately I can do this without a draft on the horses in their stalls. Spring and Fall cleaning is important too. We try to go into the winter with the cob webs and dust removed as much as possible. If it is too cold, I do not leave them out for long periods at a time. It is extra work, but give them two or three short periods out instead of one long period helps. I am talking wind chills below 0 and/or precipitation.