Cover windows, draught-proof seals, insulate hatches & roof vents, RV skirting and ventilation all insulate the camper, helping to prevent heat loss.
Merino wool mattress topper, feather & down comforter, alpaca wool blankets & flannel sheets will keep you warm & snug all night long.
Staying active will help you keep warm, reducing the amount of heating needed in the camper.
Small but powerful, portable propane heaters are ideal for boondocking with no demand on your onboard battery bank.