Lance or one of the Northwoods products. Way better insulated all round.
The problem with all TTs is that removal of moisture laden air is not addressed. At a min., you need to crack open windows & roof vents. If camping for extended periods, you need a dehumidifier (electric). A tremendous amount of moisture is released into the air from human bodies, pets, cooking & showering and if not removed will lead to rot, delamination & mold. A better insulated TT helps a lot, but never seal up all the cracks and openings to conserve heat. "Regular" TTs are just not very well insulated.
If it were me, I'd check out TTs with a Murphy bed. More space during the day and a place to lounge and watch TV. Our 1st TT was 20' and we sold it after a year because it was just too cramped. It was not enjoyable to spend time inside other than sleeping.
There was a guy that toughed out a winter in an R-pod in the Yukon. Trailer Life story
here. Not exactly the best choice for brutally cold -40C temps. He lived to tell the tale though... :)