Winter van life is less about cold and more about water. Manage moisture and heat together, and a van becomes genuinely cozy at temperatures that surprise people.
Condensation is the real enemy Every breath, every pot of pasta, and every wet jacket releases moisture into your tiny space. When it hits a cold metal wall it condenses, soaks your insulation, and breeds mold. The fix is ventilation, even in the cold. Crack a window and run your roof fan on low. Counterintuitive, but trading a little warmth for dry air keeps the whole van healthier.
Insulation that earns its space Focus on the big surfaces: ceiling, walls, and especially the floor, since cold rises through metal fast. Closed-cell foam and wool both work. The single highest-value upgrade is insulated window covers (Reflectix or magnetic panels). Your windows are giant heat leaks, and covering them at night makes a dramatic difference for almost no money.
Heat sources, ranked - Diesel or gasoline air heaters (Webasto, Espar, or budget clones) are the standard for full-timers. They are dry heat, sip fuel, and run safely overnight. - Propane buddy heaters work for short use but dump moisture into the air and require a cracked window for carbon monoxide safety. Never sleep with one running. - Good sleeping gear does the rest. A rated down quilt means you barely need to heat the air at all.
Get a battery-powered carbon monoxide detector regardless of your setup. Stay dry, insulate the glass, and winter stops being something to fear.