Beating Condensation and Damp In Your Caravan

Wake up to wet windows and a musty smell? Condensation is one of the most common complaints in full-time van life, and left alone it turns into mould that ruins soft furnishings and cabinetry. Here is why it happens and exactly how to keep your van dry through winter and the tropics.

Why Condensation Forms In a Caravan

Condensation is warm, moist air hitting a cold surface. When the air inside your van is warmer and wetter than the aluminium, glass and framing around it, the moisture in that air gives up its water the moment it touches something cold. That is the fog on your windows at dawn, the beads running down the inside of the skylight, and the damp patch behind the bedhead where the wall never quite warms up.

A caravan is a near-perfect condensation trap. It is a small, sealed metal box with single-glazed windows, thin walls and very little thermal mass, so the surfaces cool right down overnight while four bodies breathe warm air into a space the size of a bathroom. The bigger the gap between the inside air temperature and the surface temperature, the more water drops out.

Two situations make it worst. The first is cold-country winter, where freezing overnight temperatures chill every window and wall while your heater keeps the cabin warm and the air holds plenty of moisture. The second surprises people: the tropics. Up north in the build-up and the wet, the outside air is so humid that even a small temperature difference, running the air conditioner against 90 percent humidity, for instance, pulls water out onto every cold surface. Condensation is not just a winter problem.

Where All That Moisture Comes From

The water fogging your windows was inside your van the whole time. You are the main source. Two adults breathing and perspiring overnight put roughly a litre of water into the air between them by morning. Add kids or a dog and the number climbs.

Everyday living tops it up all day:

• Cooking: boiling pasta, a simmering curry or the kettle dumps steam straight into the cabin.
• Showering: an internal ensuite is a moisture bomb if the fan is not running and the hatch is shut.
• Wet gear: raincoats, towels, swimmers and muddy boots drying inside slowly release every drop back into the air.
• Unflued gas heaters: this is the big one. A portable LPG heater produces water as it burns, around a litre of moisture for every litre of gas, and pumps it all straight into your living space.

None of these are avoidable on their own. You have to cook, wash and stay warm. The trick is managing where that moisture goes rather than pretending it is not there.

Why Your Heat Source Matters

How you heat the van is the single biggest lever you have over condensation, and it is the one most people get wrong.

An unflued gas heater, the portable cabinet type or a cooktop left burning for warmth, makes the problem dramatically worse. Combustion produces water vapour, and because these heaters are unflued there is no exhaust to carry it outside. Every bit of that moisture stays in the cabin, lands on your cold windows overnight, and adds to the puddle. Run one in a closed van and you will be wiping down glass by the litre.

A diesel heater does the opposite. The burn happens in a sealed chamber and the exhaust vents outside, so not one drop of combustion moisture reaches your living space. What comes out of the vent is bone-dry warm air, which actually lowers the humidity inside the van and helps dry out damp gear rather than fogging the place up. This is why full-timers who switch from gas to diesel almost always report their condensation problem shrinking overnight.

The Practical Fixes That Actually Work

You will never stop condensation completely, but you can keep it from becoming a problem. It comes down to three things: put less moisture in, get moisture out, and warm up the cold spots where it lands. Work through these and a wet van becomes a dry one.

Ventilate constantly, even when it is cold

This feels wrong on a freezing morning, but it is the most important habit you can build. Sealing the van up tight traps every bit of moisture inside. Crack a window at each end for cross-flow, leave the roof vents open a turn or two, and never block the factory floor and wall vents that came with the van, they are there to let damp air escape. A cold, dry van beats a warm, wet one every time, and a diesel heater easily makes up the small heat you lose.

Attack moisture at the source

Run the range hood or a window fan whenever you cook, and keep lids on pots to trap the steam. Use the ensuite extraction fan during and after every shower, or better still, use the amenities block when you are on a powered site. These two jobs, cooking and washing, produce the sharpest spikes of moisture in the day, and dealing with them on the spot stops the air ever getting saturated.

Dry wet gear outside

Wet towels, raincoats, boots and swimmers hung inside will offload every drop into your cabin air over the following hours. Hang them under the awning, over a line, or in the boot instead. If they absolutely must come inside, keep them near an open vent so the damp has somewhere to go.

Run absorbers or a small dehumidifier

Passive moisture absorbers like the Damp Rid tubs sit in cupboards and under the bed, pulling water out of the air for around ten dollars a refill. They are cheap insurance in wardrobes and other closed, still spaces where mould loves to start. If you are on power and fighting serious damp, a small 12L compressor dehumidifier will strip litres out of the air a day and make a noticeable difference in a persistently wet van.

Insulate the cold spots

Condensation lands wherever a surface is coldest, and in most vans that means the windows and the metal framing. Thermal blinds or Reflectix cut across the windows raise the surface temperature enough to stop a lot of the fogging. Insulating window covers, double-glazed acrylic windows if you are upgrading, and simply keeping furniture pulled a finger’s width off the external walls to let air move behind it all help the cold spots stay warmer and drier.

Wipe down and watch for mould

Whatever water does form needs to be dealt with before it settles in. Wipe windows, sills and the skylight each morning, lift the mattress regularly to air the base and check for black spotting underneath, and keep an eye on the back corners of cupboards and the bedhead wall. Mould appears as black or grey speckling and once it is in fabric or timber it is hard to shift, so catch it early with a vinegar or mould-killer wipe.

Condensation or a Leak? How to Tell

Not every damp patch is condensation. If water keeps appearing in the same isolated spot, a corner of the ceiling, one window frame, the floor near a seam, especially after rain rather than after a cold night, you may have a leak rather than condensation. Condensation is general and follows the cold, showing up across all your windows and cold surfaces on cold or humid mornings. A leak is local and follows the water, tied to one spot and worse after rain.

Check the obvious culprits. Run your fingers around the sealant on windows, hatches, the awning rail and any roof-mounted gear, looking for cracked, lifted or perished silicone. A cheap moisture meter helps you tell a genuinely wet wall from surface fog. If a spot stays wet when the rest of the van is dry, treat it as a leak and re-seal it before water gets into the framing and does real damage.