A coop without windows ?

[aart]

Windows are good....for ventilation in summer and light in winter,
especially those days when they won't venture out due to bad weather.

Top hinged windows can be left open all summer and shut closed in winter.

Need some other ventilation that can be protected from weather and open all year round.
Open eaves venting under deep roof overhangs work very well for me here.

 

[debid]

Chickens need light to lay, too. You're already at a disadvantage being so far from the equator, adding in a dark habitat would pretty well assure a short laying season. I'd highly recommend a light that you can put on a timer and an outlet for a de-icer to plug in whether you add windows or not.

And yes, odds are it needs much more ventilation. You're venting for moisure reasons so not enough means frostbite on combs in winter.