You don't want drafts on the birds in cold weather. The air pockets in down that provide insulation are lost if they get a wind. With making a wind shield on 3 sides of your run I'd think you covered the blowing wind problem that may occur in a too ventilated coop. There's really never too much ventilation but there can be no wind.
Climate zone 3a here with no heat or insulation. Temps can hit -30F or less but that's less than a handful of nights, one to two week period of no high above singe digit is typical every winter though.
Climate zone 3a here with no heat or insulation. Temps can hit -30F or less but that's less than a handful of nights, one to two week period of no high above singe digit is typical every winter though.