How to stop condensation in a camper van in winter

Heating November 4, 2026

Why camper vans get wet in winter and how to fix it: vented heat, a small steady air exchange, window covers, humidity targets from the EPA and what owners report works.

To stop condensation in a camper van in winter, you have to do three things at once: produce less moisture inside, push the moist air out, and get rid of cold surfaces for it to land on. In practice that means a vented heat source (a diesel heater, not an unvented propane heater), a roof fan on low exhaust plus a cracked window as a fresh-air inlet, insulated covers on the windows, and wet gear kept out of the van. The EPA advises keeping indoor relative humidity below 60 percent, ideally between 30 and 50 percent, and a cheap hygrometer tells you whether you're there. You won't get rid of camper van condensation in winter completely, especially on single-glazed windows, but you can keep it from dripping into walls, bedding and wood framing.

This guide explains where the moisture comes from, which fixes actually work in a van, and what owners report from cold-weather nights.

Why vans get so wet in winter

Condensation forms when warm, humid air touches a surface colder than its dew point. A van has lots of those surfaces: glass, bare steel ribs, the back doors, the cab. And a small, sealed space fills with moisture quickly. The main sources are:

Breathing and sweating. Every occupant adds water vapor all night.
Cooking, especially boiling pasta or making coffee on a stove with no range hood.
Unvented combustion. The EPA notes that combustion appliances such as stoves and kerosene heaters produce water vapor and raise humidity unless they're vented outside. A portable propane heater burning inside the cabin adds moisture as well as carbon monoxide risk, and CDC advises never using a portable gas camp stove indoors.
Wet gear: snowy boots, a wet dog, damp towels and clothes drying inside.

Fixes ranked by impact

Fix	What it does	Rough cost	Notes
Vented heat (diesel or ducted gas furnace)	Warms the air without adding combustion moisture	High	Biggest single change if you currently use an unvented heater
Roof fan on low exhaust plus a cracked window	Swaps moist inside air for drier outside air	Medium (if you already have a fan, free)	Costs some heat; worth it
Insulated window covers	Hides the coldest surfaces from humid air	Low to medium	Glass behind a cover can still get wet; open covers in the morning
Hygrometer	Shows whether you're actually below 60% RH	Low (EPA cites about $10-$50)	Put it at bed height, away from the heater outlet
Cooking ventilation	Removes steam at the source	Free	Fan on high while cooking, lids on pots
Window vacuum, microfiber cloths	Removes water before it runs into framing	Low	Treats symptoms, not the cause
Desiccant or 12 V dehumidifier	Pulls some moisture from the air	Low to medium	Small units can't keep up with people; compressor units are heavy on batteries
Insulation and thermal breaks	Warms wall surfaces, cuts hidden condensation on steel	High (build stage)	Cover or insulate exposed ribs and pillars

How to stop camper van condensation in winter, step by step

1. Measure it

Put a hygrometer in the van and check it before bed and when you wake up. The EPA's 30 to 50 percent range is the target. If you wake up at 70 percent or more with wet windows, ventilation is too low or moisture production too high.

2. Switch to vented heat

A diesel air heater takes combustion air from outside and sends its exhaust outside. Webasto's installation rules don't allow combustion air from the cabin. So the heater warms cabin air without adding the water vapor its combustion produces. Warm air also holds more moisture before it condenses, so a vented heater both warms and dries the cabin. If you're adding one, see the diesel heater install guide for floor and seat-base placement and CO alarm advice. Running a vented heater doesn't remove moisture you create, though; it just makes ventilation easier to tolerate.

Diesel vs propane heat and condensation: the fuel isn't the issue, the venting is. A sealed, ducted propane furnace that vents outside behaves like a diesel heater for moisture. A portable propane heater, catalytic heater or stovetop burning in the cabin releases its combustion water vapor straight into the air you're trying to keep dry. If you're on a budget, ventilate harder whenever any flame burns inside, and never sleep with an unvented heater running.

3. Ventilate continuously, a little

The EPA's advice for condensation boils down to reducing humidity, increasing ventilation or air movement, insulating cold surfaces and raising the air temperature. In a van, a roof fan on its lowest exhaust setting plus a window cracked at the opposite end creates a slow, steady air exchange. It feels wasteful to throw out warm air, but warm, damp air does more damage than slightly cooler, dry air.

4. Cover the windows

Insulated covers or curtains over the glass keep warm, moist cabin air off the coldest surfaces. Expect some condensation behind them anyway, and open them in the morning so the glass dries.

5. Cut moisture at the source

Cook with the fan on high and lids on pots; boil water outside in good weather.
Keep wet boots, coats and towels in a sealed bin or outside, not drying on hooks over the bed.
Air the bedding during the day; mattresses on solid platforms trap moisture underneath, so lift them or use a breathable underlay.

6. Dry what condenses

Wipe or vacuum windows each morning before water runs into frames, and wipe the steel at the back doors. The EPA says wet materials need to dry within 24 to 48 hours to prevent mold.

7. Check hidden spots

Look behind cushions, inside lower cabinets on outside walls, under the mattress and around the back-door seals. The EPA lists walls behind furniture, where condensation forms, among common spots for hidden mold.

If mold has already started

For small patches, the EPA's basic approach is to fix the moisture source, scrub hard surfaces with detergent and water, and dry them completely. Porous materials such as foam, carpet or headliner may need replacing if mold has grown into them. Wear gloves and eye protection and avoid breathing spores. Don't paint or caulk over mold.

What people who've done it say

In a January 2026 r/VanLife thread, a builder whose windows were dripping onto wooden framing after the first night asked how to stop it. Replies agreed it can't be eliminated, only reduced. One owner described running a roof fan on vent at about 20 percent all night with the skylight slightly open, at temperatures from 10 °C down to -10 °C. They called it counterintuitive but effective: "warm and dry not warm and wet."
Several commenters in the same thread recommended window vacuums or microfiber cloths each morning, and thermal window covers or fitted pads at night. Another pointed out that covered glass still gets wet behind the cover. One said a mains-powered dehumidifier helps on a powered campsite but probably isn't practical on battery.
Another commenter in that thread stressed the heat source, recommending a diesel-type heater, and noted that breathing also puts moisture inside the walls, not just on the windows.
On a Wild Camping for Motorhomes thread, an owner felt unwell after running a diesel heater all night. Several members suggested the air had become too dry, and some said they turn the heat down or off at night and use a timer for the morning. Another member reminded them that an exhaust or combustion-chamber leak is possible and worth checking with a CO detector. That's a useful reminder that a diesel heater dries the air, and any unexplained symptoms should be checked with a CO detector first.
On the Class B Forum, a van owner who ran out of propane on a winter week fell back on a portable propane heater with a window cracked. That kind of unvented heat is the setup this guide suggests replacing, both for moisture and CO safety.

Common mistakes

Sealing the van up tight to save heat. Without ventilation, humidity climbs all night.
Relying on an unvented propane heater as the main heat source.
Drying clothes and gear inside overnight.
Leaving bare steel exposed in the living area, where it drips behind panels and rusts.
Trusting a small desiccant tub to handle two people breathing all night.
Ignoring the water system. If heat goes off while you're away, the cold that causes condensation can freeze the lines too. See how to winterize a camper van water system.

Bottom line

Camper van condensation in winter is a moisture-balance problem. Use vented heat, keep a small, steady air exchange going with a roof fan on low and a cracked window, cover the glass, keep wet gear and steam out of the cabin, and check the hygrometer: under 60 percent, ideally 30 to 50 percent. Wipe what still condenses each morning and check hidden corners for mold. For the power side of running fans and a heater all night, see the van electrical system guide.