How Do I Stop Condensation and Mold in a Van?
Condensation is physics: warm wet air hits cold surfaces and dumps water. Mold is what happens when that water stays. The fix is not a “magic dehumidifier.” It’s moisture control plus surface temperature control, every day.
CONDENSATION
Cause: humidity + cold surfaces
Driver: sleeping + cooking + wet gear
Fix: vent + heat balance
REALITY
The rule that ends the guessing
If your windows are wet in the morning, your air was wetter than your surfaces could tolerate. You fix that by moving moisture out, reducing moisture in, and keeping key surfaces warmer.
Non-negotiable: You need controlled ventilation even when it’s cold. “Sealed up for warmth” is how you grow mold.
Related:
QUICK FIX
Quickest improvements that actually work
VENT
Move moist air out on purpose
- Crack two openings for crossflow (even small).
- Run a roof vent or fan during cooking and after sleeping.
- Dry the van with airflow, not wishful thinking.
HEAT BALANCE
Warm key surfaces, not the whole world
- Keep the sleeping zone warmer than the windows.
- Stop cold-soaking the van all night with zero airflow.
- Insulate where you can; block drafts where you can’t.
MOISTURE IN
Reduce what you create
- Cook with lids and ventilation every time.
- Dry wet gear outside the living zone.
- Do not use unvented combustion as primary heat.
Fast test: If you can wipe water off walls/windows in the morning, your overnight plan is failing. Fix the routine before you buy gear.
Fast win: Airflow during and after cooking is one of the biggest single improvements you can make.
WHY
Why condensation happens in vans
Vans are thin metal shells. Metal gets cold fast. Your breath, cooking steam, and wet gear raise humidity fast. When that humid air touches cold metal, moisture condenses into liquid water.
SOURCES
- Two people sleeping can add a lot of moisture overnight.
- Boiling water and simmering adds moisture fast.
- Wet jackets, boots, and towels keep feeding humidity.
- Unvented combustion adds moisture and pollutants.
SURFACES
- Windows are the first place you see it (coldest surface).
- Thermal bridges (bare metal ribs) condense behind walls.
- Mats, bedding, and wood panels hide moisture until mold shows up.
- Closed cabinets trap humid air against cold panels.
DAILY ROUTINE
Daily condensation routine (15 minutes that prevents weeks of cleanup)
MORNING
- Vent the van immediately (two openings).
- Run a fan to purge humid air for a few minutes.
- Wipe windows and any visible wet spots.
- Pull bedding back so moisture can escape.
- Open cabinet doors briefly to air out trapped humidity.
EVENING
- Cook with ventilation and lids on pots.
- Dry wet gear outside the sleeping zone.
- Keep a controlled crack for airflow overnight.
- Keep sleeping insulation off the cold wall if possible.
- Do a quick moisture scan: windows, corners, under mattress.
Mattress warning: If you have moisture under your mattress, you’re already in mold territory. Add airflow under the mattress and stop sleeping on a cold, sealed platform.
COOKING
Cooking without soaking your van
STEAM CONTROL
- Use lids. Steam you keep in the pot is moisture you don’t have to remove.
- Vent during cooking, not after you’re done.
- Prefer lower-steam meals when conditions are cold and damp.
- Wipe condensation around the cook area immediately.
GREASE CONTROL
- Grease films hold moisture and feed odor problems.
- Use a splash guard and keep cook time tight.
- Wipe surfaces while warm, before residue hardens.
- Store cooking gear dry, not in a sealed humid cabinet.
SLEEPING
Sleeping moisture and bedding control
Sleeping is a major humidity source. Your goal is to prevent warm, wet air from being trapped against cold surfaces (walls, windows, mattress base).
BEDDING
- Keep bedding off cold metal and cold glass.
- Air out your sleeping system daily if you see dampness.
- Avoid storing damp blankets in sealed bins.
- If you wake up clammy, you’re trapping moisture.
UNDER-MATTRESS
- Create airflow under the mattress (slats/mesh/air gap).
- Check corners weekly for dampness and smell.
- Dry the platform if it’s wet before you sleep again.
- Don’t seal the bed base like a cooler.
INSULATION
Insulation and thermal bridging (where hidden mold starts)
THERMAL BRIDGES
- Bare metal ribs and framing stay cold and condense behind panels.
- Cabinets against exterior walls trap humid air against cold surfaces.
- Look for cold corners, not just wet windows.
- Air gaps without airflow can still condense and stay wet.
PRACTICAL FIXES
- Seal drafts and control airflow paths.
- Keep interior surfaces warmer with insulation where feasible.
- Leave small ventilation paths behind cabinets where possible.
- Reduce moisture input so the system has less to fight.
DEHUMIDIFIERS
Dehumidifiers: what they can and can’t do
CAN HELP
- They reduce humidity when the van is closed up.
- They can help dry the air after cooking or sleeping.
- They are useful when you have stable power and time.
CAN’T FIX
- They don’t solve cold surfaces and thermal bridging.
- They don’t stop moisture created faster than removal.
- They don’t replace ventilation during cooking.
- They won’t prevent mold if you keep storing damp gear inside.
Reality check: If you rely on a dehumidifier but still wake up to wet windows, your airflow or moisture input is still failing.
MOLD
Mold cleanup and prevention (keep it controlled)
CLEANUP
- Identify and dry the source area first, or it returns.
- Ventilate during cleanup to avoid breathing spores.
- Clean hard surfaces thoroughly; replace porous items that stayed damp.
- Check hidden zones: under mattress, behind panels, inside cabinets.
PREVENTION
- Keep a daily airflow routine in cold and wet weather.
- Stop storing wet gear inside the living space.
- Keep surfaces warm enough to stay above condensation conditions.
- Do a weekly moisture check before it becomes a project.
STOP DOING
What to stop doing (because it creates the problem)
- Sealing the van tight overnight with no planned airflow.
- Cooking without ventilation because it’s cold outside.
- Using unvented combustion heat as your primary heat plan.
- Leaving wet towels, boots, and jackets in the sleeping zone.
- Ignoring moisture under the mattress until it smells.
- Assuming “I’ll just wipe the windows” is a solution.
Simple target: wake up to dry windows most mornings. If not, reduce moisture input and increase controlled airflow.
If you only do one thing: ventilate during cooking and do a morning purge. That alone prevents a large share of van mold problems.