It is the first thing every autumn camper learns: in the morning the windows are streaming, the pillow is stuck to the wall, and somewhere the roof vent is dripping. Condensation is not a design flaw in your camper, it is physics. And physics can be outsmarted.
Where the water comes from
Two sleeping people release almost a litre of water into the air every night, through breathing and through their skin. Add cooking, wet jackets and the dog. Warm air holds this moisture; when it hits cold surfaces (windows, sheet metal, poorly insulated corners), it condenses there. The water on the window was in your lungs before, that is how simple and how unavoidable it is.
The four countermeasures
1. Ventilate, always: keep a window or roof vent open a crack, even when it is freezing, so the air exchange carries the moisture out before it condenses. Five minutes of cross-ventilation in the morning works wonders. 2. Take the edge off cold surfaces: thermal mats on the windows are condensation killers, because they cover the coldest surface in the vehicle. 3. Manage sources of moisture: wet clothes go up front in the cab, cook with a lid on, dry towels outside. 4. Get air under the mattress: an anti-condensation mat or slatted base stops the underside of the mattress becoming a hidden moisture trap, which is where mould starts first.
When it gets serious
A hygrometer costing a few francs makes the problem visible: if the humidity inside stays above 65 percent, it is time to act. A musty smell or black spots on seals or behind cushions are late warnings; by then only thorough drying, cleaning and an honest search for the cause will help. Better not to get that far in the first place. Ventilating costs nothing, getting rid of mould costs a fortune.
💨 Bonus tip for parking heaters: if you have a diesel air heater, use its ventilation function even when you are not heating. Details in Johannes' experience report.
Background research including the roadsurfer blog and guides from TCS, VanSite and other camping magazines; text and analysis: Parkn'Sleep editorial team.
