Walkerkm, we're in the south, so it's pretty mild in the winter. Dh wants to configure something to close off the long vent though. I'm not sure we need too, I think it might get too "stuffy" in the coop with no ventilation at all.
I have a tiny little coop, but still needed ventilation obviously. You can see the vent under the roofline just above the nest box. We also have "windows" on each side of the coop that can be opened and closed depending on the season.