How to Stop Condensation and Damp in a Caravan Over Winter
Condensation in a caravan is not a sign that something is broken. It is physics. Warm air holds more moisture than cold air, so when the warm, damp air inside your van meets a cold window or a cold wall, the moisture comes out of the air and onto the surface. Left alone, that is how you get black mould in the corners and a musty van by February.
Four people sleeping, cooking and breathing in a touring caravan put a surprising amount of water into the air overnight. The job in winter is to produce less of it, get more of it out, and stop the surfaces being cold enough to catch it.
Where the moisture comes from
- Breathing. Unavoidable, and the largest single source overnight in an occupied van.
- Cooking. Boiling pans put water straight into the air. A pan of pasta releases more moisture than anything else you will do all day.
- Washing and showering. Concentrated and obvious, but at least easy to vent.
- Drying clothes indoors. Every gram of water that leaves a wet coat ends up on your windows.
- Flueless gas heating. Burning propane or butane produces water vapour as a combustion product. A gas heater warms the van and humidifies it at the same time.
- Wet kit brought in. Boots, awning groundsheets and dogs.
The three levers that actually work
1. Ventilate, deliberately and briefly
The instinct in winter is to seal everything. That is precisely wrong. Never block the fixed roof and floor vents. They are a legal and practical requirement, and they are the reason the van does not turn into a terrarium.
Beyond that, ventilate in short bursts. Open two windows on opposite sides for five to ten minutes, twice a day, and let the humid air exchange for dry outside air. Because you are exchanging air rather than cooling the fabric of the van, the temperature recovers quickly. A permanently cracked window does the opposite: it cools the surfaces steadily while barely shifting the air.
2. Produce less moisture in the first place
- Put lids on pans. It is the single highest-return habit in a winter caravan.
- Shift some cooking to enclosed methods. An air fryer puts far less water vapour into the cabin than boiling or frying.
- Do not dry washing over the heater. Dry it in the awning, or use a site dryer.
- Leave wet coats and boots in the awning or the porch, not in the van.
- Run the extractor or open the roof vent while showering, not afterwards.
3. Keep surfaces above the dew point
Condensation forms where the surface is colder than the dew point of the air. Raise the surface temperature and it stops forming even if the air is humid.
Gentle, continuous background warmth beats short bursts of intense heat. A thermostatically controlled electric heater holding the van at a steady temperature keeps the walls and window frames warm enough that moisture stays in the air, where the ventilation can carry it away. The Ceramic Heater MKK-230 has 500W, 1,000W and 1,500W settings plus an adjustable thermostat, so it can sit on a low setting and cycle rather than blasting and stopping.
Electric heat is also dry heat. A resistive element adds no water to the air at all, which is the key difference from flueless gas.
Why gas heating makes condensation worse
Burning hydrocarbon fuel produces carbon dioxide and water. A flueless gas heater releases both into the room it is heating. Mestic's gas models run at 1.4kW, 2.8kW and 4.2kW, and the MRK-100K listing quotes a gas consumption of 305 g/h at 4.2kW. A meaningful proportion of that mass ends up as water vapour in your caravan.
That does not make gas the wrong choice, and off-grid it is often the only choice. It does mean that if you are on a hook-up and fighting damp, switching the background heat to electric removes a moisture source rather than just masking it.
Gas heaters also require permanent ventilation and a working carbon monoxide alarm in the space. Neither is optional.
The specific cold spots to watch
- Window frames and the bottom edge of every window, especially single-glazed ones.
- Behind and underneath mattresses and bench cushions, where air cannot circulate. Lift them regularly.
- Inside wardrobes and lockers on the outside wall. Leave the doors ajar.
- Corners of the ceiling, where two cold surfaces meet.
- Around roof lights.
- Behind anything pushed hard against an exterior wall.
Wipe standing water off windows in the morning rather than letting it run into the frames. That single habit prevents most of the damage, because it is water sitting in the frame over weeks that causes the staining and the smell.
If mould has already appeared
Clean it off promptly with a proprietary mould remover suitable for the surface, dry the area thoroughly, then fix the cause. Cleaning without changing the ventilation or heating pattern means it returns in a fortnight. Persistent damp in the same spot, particularly if it is soft to the touch, may be water ingress through a failed seal rather than condensation, and that is a different repair.
A workable winter routine
- Morning: wipe the windows, open two windows opposite each other for ten minutes.
- Lift or tilt the mattress and cushions so the undersides can dry.
- Cook with lids on, and vent while cooking rather than after.
- Keep a low background heat on rather than heating hard then letting it go cold.
- Evening: another short cross-ventilation before bed.
- Leave a locker door or two ajar overnight.