6 person tent that's 32 sq feet. I'm not planning on taking it below 20 degrees. If it gets that cold I'm packing up and going home.
For a tent that small, I would go with a propane heater and a little ventilation, unless you were camping for weeks on end.
This is what I do, and it has worked down to -10, with a proper sleeping bag ( I use my army issued intermediate cold Mummy bag). Light the propane heater. Once warm, change into my sleeping clothes consisting of fleece pajama pants, a sweatshirt, a clean pair of thick wool socks, and a fleece watch cap. Open up my sleeping bag and lay a wool blanket inside (I think mine is an old east German army blanket, but I have used the US ones as well. Lay down, wrap up in the blanket, zip the bag most of the way, reach out and shut off the heater, then zip up all the way. Be warm as hell until morning when I reach out with one arm, light the heater, thank the man who invented push button electric ignition, and retreat back to my bag for another 10ish minutes, then get up, get dressed, shut the heater off, and go about my day.
