My coop is the south end of our pole building...measures 7'x16' for 41 hens. There are 4 insulated south-facing windows, entry door on the west and wall fan-vent on the east side that stays on (draws out the air) 24/7. Up until this point, the night-time routine is to leave 2 of the windows cracked (about an inch) with the vent running. Once freezing temperatures set in, is it going to be OK to leave that fan vent running or should it be turned off with windows left cracked for ventilation?? I'll get a picture posted soon... Thanks!