You wake up in the camper, draw the curtain and the windows are soaking on the inside. You touch the wall and it's damp. And if you lift the mattress, sometimes that awkward damp patch appears underneath. Condensation is one of the most common and most annoying problems of camper life, especially in winter. The good news: it's easy to understand and it can be cut down a great deal.
Why condensation appears
It's pure physics. The warm air inside holds water vapour (which you produce by breathing, cooking or drying clothes). When that warm, humid air touches a cold surface — the glass or the van's metal skin — the vapour turns into droplets of water. The greater the temperature difference between inside and outside, and the more moisture you generate, the more condensation. That's why on a cold winter night, with two people sleeping inside, it appears without fail if you do nothing.
Fix 1: ventilation (the most important)
It sounds contradictory when it's cold, but it's the number one measure: you have to renew the air to get the moisture out. That doesn't mean sleeping with the door open, but keeping a minimum, constant flow: a window slightly ajar, a roof fan or the ventilation grilles all do the job. Swapping humid air for dry air from outside breaks the cycle.
Fix 2: insulation and vapour barrier
Good insulation reduces the cold surfaces where water condenses: if the interior wall isn't freezing, the vapour has nowhere to turn into a droplet. And the vapour barrier, fitted on the inside face, stops vapour reaching the cold metal. These two points are decided when you convert the van; we cover them in how to insulate a camper van.
Fix 3: generate less moisture
- When cooking, ventilate and put lids on pans: boiling water fills the air with vapour in minutes.
- Don't dry wet clothes inside without ventilating; it's an enormous source of moisture.
- Air the mattress: the vapour you give off while sleeping stays underneath. A slatted base or spacer matting under the mattress lets air circulate and prevents that damp. Lift it now and then so it can breathe.
Fix 4: the right heating
The type of heating matters. Room-sealed combustion heaters (diesel parking heaters) add no moisture to the interior, whereas certain heat sources do. Warming the space a little also reduces condensation, because it raises the temperature of the surfaces. We look at this in heating for a camper van.
An extra trick: moisture absorbers
Tubs of moisture-absorbing salts help as a backup, above all when you leave the van closed up and standing. They're no substitute for ventilation, but they add to it, and they stop damp building up while you're not using it.
In short
Condensation appears when humid interior air touches cold surfaces, and it's fought on four fronts: ventilating (first of all), insulating properly with a vapour barrier, generating less moisture and choosing heating that doesn't add any. The step you can take today: tonight, leave a window or vent slightly open to create airflow; it's free and you'll notice the difference when you wake up. And if you're converting a van, sort the insulation out properly from the start.
