We use a Olympian Wave 6 Catalytic Heater (on low) in our 32' 5W when "boondocking" in AZ all winter. Uses no electricity (quiet as in no noise) or emits no carbon monoxide but they do consume O2. Crack open a high window at one end and a low window at the other end of the RV. With 80 gal FWT and the impurities in the drain tanks it doesn't get cold long enough to worry about any freeze ups in the unheated tank area.
I would assume that a Wave 6 Wave would keep you toasty warm in your class C.
2005 Dodge, 2500, auto, 2wd. Pac brake PRXB. CB, Max Brake Brake Controller, Rhino Lining, Aero 60 gal. replacement tank.
1998 Hitchhiker ll, mod#31RLBGBW, RBW L'tl Rocker Hitch, Generac NP50 G generator