Welcome!! Beautiful flock. And imo there is no such thing as too much ventilation, the more the better. And in fact, the cold air is much less of a concern than the hot humid air that can build up without enough ventilation. Although that being said you do need to make sure that the vents aren't blowing on the roosts. The roosts should be at least 12-18 inches below the vents so it doesn't blow on them but still above the nest boxes. I have heard some say there should be a 1 square foot of ventilation per bird (permanent, open all the time unlike windows) but idk how true that is. Besides that i dont think they need insulation or heat. I don't do either though i only got mine in October. And actually i did bring them in 2 nights when it was -5 out and -30 windchill but they were babies and the coop is a junk coop, with the new one we're building and now they're older i wont do that. Insulation I think can make the coop too warm and trap moisture which they dont need but then again with the proper ventilation it might not do that and might just take the edge off the cold which could be good but not necessary. But heat I wouldn't use because if the power goes out or something then they aren't acclimated to the cold and could get sick or die.
