Good draft free, well vented housing is what is key, i also fully agree on breeds, choosing cold hardy ones will make the whole process easier on everyone. My big hens don't have an insulated coop, other than whatever the R factor would be of the fancy paneling the coop was made from lol I have venting and i chose a flat roost so they fluff down on their feet at night.
We've had some not so nice weather even this week, they go about their day free ranging and come back at dusk, this isn't their first winter and mine get pretty cold(winters) there are colder areas but frankly past -22C i am am froze so colder is only worse, i do not heat or light my birds, will often toss BOSS into the coop floor just before bed so they can clean that up. You have a pretty good sized flock, way more than I.. only keep 4 standard chickens right now... yes, a drop compared to most here. We do have silkies as well, but they have yet to winter(all youngin's) so far those have tolerated the cold we had, no heat, no fancy gear.
There is a good ventilation page, i must find it for you.. to Quote my daughter recently who lifted up a hen in our recent cold snap, "wow, is she ever warm" as she tucked her hands under the birds wings, it was cold here below freezing, it shocked her, i knew they were warm as they were happily behaving as they always do. Watching your animals is key to see how they are coping and i mean all of them, us sadly suffer the most, i wish i could carry a chicken all day in my hands lol
Here link to the page on ventilation.
https://www.backyardchickens.com/a/...-go-out-there-and-cut-more-holes-in-your-coop