How to Stop Condensation and Damp in Your Caravan Over Winter

Winter Damp Guide

A practical guide from Bedam Leisure — caravan & motorhome specialists

Wake up on a cold morning, draw back the blind, and there it is: a film of water running down the inside of the window, beads of moisture on the rooflight, and that tell-tale musty smell. Condensation is the single most common winter complaint we hear about — and left unchecked, it's also the quiet beginning of the damp that ruins woodwork, soft furnishings and resale value. The good news is that it's almost entirely preventable, and you don't need anything exotic to beat it.

Here's how condensation actually works, and exactly what we'd do to keep a caravan, motorhome or campervan dry right through the British winter — whether you're touring in it or it's parked up in storage.

Why condensation happens (and why winter makes it worse)

Warm air holds moisture; cold air can't. When the warm, damp air inside your van meets a cold surface — a single-glazed window, a metal window frame, the underside of a rooflight, a chilly outside wall — the air right at that surface cools below its dew point and the water vapour turns straight back into liquid. That's the film you wipe off the glass. In winter the gap between your cosy interior and the freezing world outside is at its widest, so the cold surfaces are colder and the condensation is heavier.

And there is a lot of moisture to deal with. Two people simply breathing and sleeping overnight can put out the best part of a litre of water vapour. Add a kettle on the boil, a pan of pasta steaming away, a hot shower, wet coats and boots by the door, or a damp dog back from the beach, and the air inside fills with moisture fast. Drying laundry indoors is the worst offender of all. None of that is a fault with your van — it's just physics, and the fix is to manage the moisture rather than trap it.

1 Ventilation

Air it out — never seal it up

The instinct on a cold night is to close everything and shut the draughts out. Resist it. Ventilation is what carries moisture-laden air out of the van before it can settle on a cold surface, and it's also a genuine safety system. Modern touring caravans and motorhomes are built to European ventilation standards (BS EN 1646 and BS EN 721), with permanent low-level vents near the floor and high-level vents or rooflights up top. Air drawn in low and pushed out high keeps a constant gentle change of air moving through.

Those vents are not optional and must never be blocked or taped over. As well as letting moisture escape, they let the products of combustion — including carbon monoxide from gas heaters, hobs and fridges — get out safely. Sealing a van to keep the heat in is both the surest way to grow damp and a real danger. Crack a roof vent open, leave the floor vents clear, and open up the windows for ten minutes when you arrive or after cooking.

If your van only has passive vents, a powered roof vent earns its keep in winter — running it on a low setting for a while after cooking or showering clears the moist air far quicker than waiting for it to drift out on its own. A handle-operated rooflight with built-in forced ventilation does much the same job and floods the van with daylight on dark days.

2 Moisture control

Soak up what's left

Ventilation does the heavy lifting, but in a small, sealed-up space — especially one stood empty in storage — a dehumidifier mops up the moisture that's left in the air. For most owners a simple passive (refillable crystal) dehumidifier is perfect: there's nothing to plug in, nothing to run, and they keep working in the cold when an electric unit can't. You sit one in the van, the crystals draw moisture out of the air and collect it as water in the base, and you pour it away when it fills. They're the cheapest insurance against winter damp you can buy.

For a bigger van, or to leave one in each end while it's stored, step up to a larger-capacity trap and keep a bag of refill crystals on the shelf so you're never caught out mid-winter.

Empty in storage? Stand a moisture trap at each end of the van, lift seat cushions on their edge so air can get round them, and prop interior doors, lockers and the fridge door ajar. Moving air is dry air.

3 Background warmth

A little heat goes a long way

Condensation forms where surfaces are cold, so keeping the inside of the van just a few degrees above the outside makes a real difference — the windows and walls stay above dew point and the water never forms. If you're touring through winter, a gentle background heat from your Truma or Alde system, left ticking over rather than blasted on and off, keeps the fabric of the van warm and dry. Even when the van is in storage with a hook-up available, a thermostatically controlled tube or frost heater set low is a tried-and-tested way to keep the chill (and the damp) at bay.

4 Habits

Small habits that make the biggest difference

Most of beating condensation is free. Pop a lid on pans when you cook — it slashes the steam and saves gas. Never dry washing inside; it's the single biggest moisture source you can control. Wipe the windows and rooflights down first thing each morning and wring the cloth out outside, so that water leaves the van rather than re-evaporating into it. Keep a microfibre cloth handy by the door for wet coats and dog towels. And when you pack the van away for a few weeks, give the inside a wipe round, make sure it's properly dry, and leave cushions and lockers open so air can circulate.

Finally, keep an eye out for the difference between condensation and genuine damp ingress. Condensation sits on cold surfaces and wipes away. If you find soft, dark patches around windows, roof seams or the floor that feel damp to the touch and won't dry, that's water getting in from outside — worth checking your seals and, if in doubt, having a habitation damp check. We cover spares and sealants for that in our cleaning & maintenance range, and rooflight and window seals in windows & blinds.