Being in snow country, when snow covers those vents on roof, you have no venting at that point. It is in my opinion and many others will agree to place vents on gable ends.(provided your coop is constructed in such fashion). Venting at the eves is also ideal, since it will not get blocked easily. It is also good to have a small vent opening at bottom of coop to allow for take-in air.
Good ventilation means a good free airflow, without drafts or wind to ruffle chickens feathers.
I do not know how your coop looks, therefore I am only suggesting what is commonly known about ventilation.
If your coop is not exactly tightly sealed, and there are cracks, and other small openings allowing air to enter, you may have sufficient venting.
If you smell ammonia inside coop, or if you see condensation inside on the walls of your coop, that would mean insufficient venting.
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
