Winter tent(ing)...eh?
Lots of good info in this thread.
One issue, WINDS/DRAFTS, needs a little more, I think.
The Inuit of the Arctic Circle areas use igloo and tents, down to -70 f. in the past decades. They always cut snow/ice blocks and build an L-shaped wall on the upwind corner, with the opening away from that corner. This usually was built as high as the "eve" of whatever tent they had.
They also ALWAYS rigged some form of an "air-lock" at the entrance, where all the heat inside was not flushed when someone entered or left. Winds up there could sit on 65+ mph for days on end...and, the snow moved every time, in great quantities... Drifts could easily DOUBLE the height of any obstacle found out there on the flat tundra (no trees in this neighborhood!).
There is no wood..hence, no fire...sometimes they would use a whale oil stove to cook something, usually not. Same type of lamp... (these were the old days, just after WW-II and into the 60's)...today, it's led lights, snow machines in place of dogs and a sled, and propane cyc everything.. They slept in their parkas and mukluks, sometimes they would let a dog come inside with them, if it was really cold. Chill factors were constant -80 or lower.. yet, no one froze. Biggest problem was getting drifted in solid...no air circulation at all, and suffocate.
I have seen wall tents, used for crews in the bush for months on end, "walled in" with straw bales on 3 sides...with some sort of "second roof" across those bales that can shed snow load. I have also seen small wood-burners used in such tents with proper pentrations and exhaust stack height...(minimum of 2ft ABOVE the peak of the roof.). The real key to usability appeared to be the wood pallets under the sleeping floors...with straw stuffed up in there too.. This was in the land of permafrost... IF you got a spot warm with your body heat overnight, you might wake up in a mini-lake, eh?...very wet and cold!..
There is a Montana Tent and Canvas company over by Belgrade/Bozeman, MT which appears to be substantial... Nothing that "works" will be cheap!...Don't be fooled and left with a very cold camp the first time out!.. Making mistakes at -25f. and colder will result in the loss of body parts...painfully. Check-6