The two previous posters, have more experience than I with a class c in the cold, though we could talk (a lot) about 5er’s.
That said.... we didn’t want to do extensive ( have too many projects now) modifications, so we went with the Bigfoot Class C. The previous owners (avid cross - country skiers) used it (ours now) down to -17 F, with the water system filled and useable.....with very minimal modifications. The “only” thing that they did was to put a little “foil bubble insulation” in a few “strategic” locations, mostly inside the outside bay access doors.
We wanted to test it ( to well below 0 F)last winter, but used it only down into “single” digits! No problem!
Several of the reasons we went Bigfoot was, enclosed, heated tanks and dump valves, one of largest ( if not the largest) fresh water tanks in the class c’s, dual pane windows, and on the E 450 chassis ( many class c’s are on the 350).
The “BIG” negative is that Bigfoot ( although back from the dead) went out of business in ‘09 ( ours is an ‘07). They, while back in business, no longer produce class c’s. Everyone’s loss!
Todd & Marianne
Miniature Schnauzer's - Sundai, Nellie & Maggie Mae
2007 Dodge Ram 3500, 6.7 Cummins, 6 speed manual, 3.73 ratio, 4x4
2004 Teton Grand Freedom, 39'
2007 Bigfoot 30MH26Sl