Personally, I don't bother.
I let any birds that will get frostbite get it their first winter. Then there's no more issues; no more partially frozen combs every year and work to keep them only partially frozen.
I suggest being smarter than me and starting with breeds that have combs appropriate for the climate.
Another Canadian and I were theorizing on some reasons why maybe adding too many vents is not a good idea, but there is not much in the way of solid evidence, and what we do have flies completely in the face of the conventional keep-your-birds-in-a-wind-tunnel advice, lol. I'll elaborate once we have some more solid data if it agrees with the theory.