Condensation and moisture in a van can lead to poor health, mould and even rust if not managed well.
Waking up on a cold morning with condensation running down your windows and clinging to every cold surface is no fun.
And if you live in a van full-time or spend long periods in cold climates, this moisture will play havoc with your health and pride & joy unless you handle it properly.
While there’s lots of things you can do to mop up the moisture, prevention is better than cure.
So how do you stop condensation in van?
What is condensation?
Before we can work out how to stop condensation in a van, it’s helpful to understand what it is and what causes it.
In the most simplistic terms, condensation occurs when air, saturated with water vapour, touches something cold, transforming the vapour to liquid.
There’s basically 3 things at play here worth understanding a little:
- Relative humidity
- Water vapour sources
- Dew point
This term refers to the amount of water vapour air can hold before it becomes saturated.
When the air is saturated, it can’t hold any more water vapour.
Relative humidity is determined by temperature. The warmer it is, the lower the relative humidity and the more water vapour the air can hold.
The more water vapour the air can hold, the less condensation will form.
So to lower relative humidity, we need to increase the temperature.
Water vapour sources
When you’re inside the van on a cold day, the interior will become warmer than the outside simply because you’re in it.
Your body heat alone will increase the temperature as well as cooking or running any kind of heater.
A good thing in avoiding condensation in theory but there’s more to it.
These daily activities of living in a van create water vapour too.
An adult can produce as much as 1 pint of water every night just from breathing!
Wet coats and boots, cooking, showering, washing up and even using propane all add water vapour inside the van.
So while the temperature may increase, so does the relative humidity because the air has become more saturated.
This is the temperature to which air must be cooled to become saturated with water vapour.
In your van, the warm air, filled with water vapour comes into contact with a cold surface like a window.
This cools the warm air, reducing its ability to hold water vapour.
Once it drops to a certain point, the water vapour becomes liquid, forming condensation.
This point is known as the dew point.
Why does condensation form on the outside of your van?
That’s because the warm humid air outside, hits the cold surface of the van body or its windows, reducing its dew point and condensing any water vapour.
Why does frost form on the inside of the windscreen?
Have you ever woken up in the morning to find frost on the inside of your windscreen? It makes defrosting a bit of a nightmare but why does this happen?
If the windscreen is really cold – the condensing water vapour freezes, creating a thin film of frost.
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How to stop condensation in a van
In reality, stopping condensation in a van completely is easier said than done.
Taking the above points into consideration there’s a few things you need to control to stop or at least minimise the condensation in your van.
- Campervan ventilation & airflow
- Controlling moisture in a campervan
- Keeping your camper warm
Campervan ventilation & airflow
Excellent campervan ventilation and airflow is the best way to stop condensation and the only way to effectively win the battle.
A well ventilated van combined with constant airflow, draws in fresh drier air, expelling humid, moisture laden air.
An effective camper ventilation system will have at least 2 openings – an intake and an exhaust.
Air is drawn in from the intake creating airflow towards the exhaust.
Install a roof vent
If you’re serious about stopping condensation in your van you’ll install one or two electric roof vents.
The range of electric roof vents varies a lot as does the features each offer.
They have features like automatic rain sensors, remote control, adjustable speeds and climate control.
We have 3 roof vents in our Sprinter van conversion.
One is above the kitchen so we use it whenever we’re cooking in exhaust mode to draw out the rising steam.
The other is above the living area which converts to our bed at night. When we’re cooking, we have this vent drawing air in towards the exhausting fan in the kitchen.
At night, we run the vent above the bed in exhaust mode, drawing out our breathe.
We have a a third vent in the bathroom though we don’t use an indoor shower, it works great for airing wet coats, towels & boots.
The best roof vent on the market is the MaxxFan 7500k.
With 10 settings, the rain cover allows it to continue to operate even when rain is lashing down outside.
Open a window
If you’ve only one roof vent installed, you still need another ventilation opening to create the airflow necessary to minimise condensation.
Opening a window in the van is an easy solution.
We have our windows almost permanently open when we’re in it, even with 3 roof vents.
Added wind deflectors protect the interior of the van from the rain. They also disguise the fact the window is open, so opportunistic thieves won’t as easily notice the security lapse.
It’s not 100% safe but it helps.
12v fan or battery operated fan
Adding a portable 12v fan to your condensation fighting arsenal can help too.
Alone, it’s never going to be enough to eliminate the moisture but it will help increase airflow, especially if you place it in front of an open window.
Controlling moisture in a campervan
Given moisture in the van is the source of condensation issues, controlling how much water vapour you produce makes the fight easier.
It’s worth considering this during your build so you can make design, fuel and appliance choices with this in mind.
Here’s a few ideas on how you can help reduce how much moisture and water vapour you produce in the camper.
Avoid propane heaters & cookers
Burning propane produce a LOT of water vapour – about 1 pint of water for every pint of fuel burnt!
That’s shed loads.
Portable propane heaters and cookers tend not to be vented so all that water vapour is staying in your van.
If you’re thinking of installing a propane burning cooker or heater, think about how much time you expect to spend in cold weather conditions where condensation will become a problem.
With the best will in the world, you’ll need an awful lot of ventilation to get rid of that amount of water vapour.
We have an externally vented diesel heater and cooker in our van so avoid any additional moisture in this respect.
Take a look at our detailed post on heating for campervans to find the best dry heating option for your conversion.
Avoid cooking inside your van
We know this is a really tough one.
You’ve built a van with an all singing, all dancing kitchen then we come along and suggest you don’t use it.
Condensation is only a problem in the cold so it’s not like we’re suggesting you should never cook in your van.
Just try to reduce how much cooking you do inside when it’s cold, if possible.
When it’s really cold and you have no choice, up the ventilation and airflow when you’re cooking.
Open the doors and windows and put those roof vents to work. If it’s especially cold, turn the heater on.
You can close up as soon as you’ve stopped cooking so it won’t get too uncomfortable.
Use a pressure cooker
Aside from saving fuel and time, a pressure cooker also emits considerably less water vapour into the van than other cooking methods.
Make sure you allow the built up pressure to release naturally though.
While we’re talking about kitchen stuff, when you boil the kettle, fill up your flasks so you don’t have to boil it again for a 2nd cup of coffee.
Avoid showering inside your van
Indoor showers for campers obviously produce a lot of steam.
Even with a dedicated extractor fan in the campervan bathroom, it’s probably asking too much to expel all the steam from one shower.
Wherever possible, shower outdoors or use campsite facilities.
If you can’t help it, keep your bathroom door closed and all the extractor fans and roof vents running for at least a couple of hours after taking a shower.
Don’t hang wet clothes & towels
Van life laundry has its challenges but we never hang wet laundry indoors, regardless of the weather.
But when living in the van in winter, wet coats and boots are unavoidable. Wherever possible, shake off as much moisture before you bring your wet gear into the van.
Better still, if there’s a safe covered area available, hang your gear in there until it’s dry.
When we can’t avoid bringing damp coats and boots indoors, we put them in the bathroom and turn the extractor fan on for a few hours.
It’s not ideal but it’s better than nothing.
Check for leaks
Especially important when buying a campervan, check the vehicle for leaks.
If you’re buying a pre-loved camper, if there’s any signs of leaks (past or present), we recommend giving it a wide berth.
Always carry a spare tube of Sikaflex for emergency leak repairs too.
Keep things clean & dry
Keeping the inside of your campervan clean and dry isn’t just more hygienic, it helps reduce moisture in your van too.
Dry up as soon as you’ve finished washing up and put the tea towel outside to dry.
Don’t put things away if they’re damp.
Use a dehumidifier
A dehumidifier works by chilling the surfaces inside it so water vapour condenses on it.
A removable tank collects the condensed water so it can be easily emptied.
We’ve never used a dehumidifier because any of the 12v versions we’ve seen don’t get terrific reviews.
A mains powered dehumidifier designed for use in a house would be a better option but they draw so much power, they’re not practical for off grid living.
If you expect to spend the colder winter months on shore power hookup though, they’re probably ideal.
Let us know if you’ve used a dehumidifier in your van and if it was effective.
Keeping your camper warm
We’ve explained how low temperatures help create condensation so keeping warm is a key part of how to avoid condensation in a van.
Go somewhere warm
This is the ultimate way to stop condensation in a van. Avoid the conditions that create it.
Head south for the winter months, if you live or travel in the northern hemisphere and north if you’re in the southern hemisphere.
Of course, that’s not ideal if you love the snow and skiing but it’s a guaranteed solution we’d be amiss to not mention.
Camper van heaters
Keeping your van warm will help to reduce relative humidity, and so stave off condensation.
We’ve already mentioned how moist heat from propane heaters produces water vapour so these aren’t ideal.
Install vented heaters that produce dry heat like a Webasto, Espar or Propex.
The water produced by the combustion is vented out of the van so not adding moisture to the air.
If you want to boondock in winter, check out our other tips on how to heat a camper without electricity.
Cover your windows (or not)
This is a tricky one.
We have a converted minibus and so have windows all round our van.
We wouldn’t change it. We get fantastic daylight so even on wet, gloomy days, we don’t feel claustrophobic and keep the view.
The downside of the windows though is their thermal protection – or more accurately, their lack of thermal protection.
So to help keep the van warm, you could cover your windows with insulated shades.
The downside of this, is you WILL get condensation behind the shades because the warm heated air of the van won’t reach the glass.
So what do we do? We have insulated curtains on our windows in the back. They allow enough air to circulate to prevent condensation on the windows.
We have a thermal curtain between the living quarters and the driving seats so when it’s especially cold, we close these over.
Air can still circulate so as to avoid condensation though the temperature is much lower in the front than the back.
We do suffer with condensation in the front from time to time, but generally when the outside temperature is really low i.e. -5°c and colder.
Cover exposed metal
Condensation forms on cold surfaces.
Any exposed metal inside your camper will probably be the coldest surface in your van.
By covering as much as possible, be that with insulation, fabric or other lining material you reduce the surface area for condensation to form.
It also helps you more effectively warm the interior.
“Solutions” to avoid
Some advice out there pushes a couple of things we think are at best a waste of money and at worst, downright problematic.
A vapour barrier is basically a big waterproof sheet fitted on top of the van’s insulation and beneath the lining.
It’s intended to stop condensation reaching the metal walls of the van so preventing rust.
In reality, installing it so it is completely watertight is almost impossible so at least some moisture will get through.
You might think preventing most of the vapour reaching the metal is better than nothing but we don’t agree.
Behind the vapour barrier, air can’t circulate as well as without it. So any water that does condense behind it, is likely to sit there for a long time.
Time enough to cause isolated spots of rust and mould.
A well ventilated space with good air flow gives any water vapour a far better chance at evaporating than having a vapour barrier.
Our advice is to give vapour barriers a miss altogether. But don’t shoot us down in flames for going against the grain on this.
You know those little silicon gel pads your get in a shoe box or new electronic devices?
The tiny amount of excess moisture they can hold won’t save your van from condensation so save your money!
How to stop condensation in a van in storage
When your RV, campervan or motorhome isn’t in use condensation is much easier to avoid.
There’s no water producing activities going on like breathing, cooking and showering so the only moisture you need to worry about it what is already in there. And leaks.
If you’re winterizing your camper for storage during the colder months, there’s a few things you should do to ensure you don’t return to a mildew infested van come spring.
- Keep at least 2 vents open | Crack a window an inch or two and leave your roof vents open if you’re under cover or have fitted rainproof vents like the MaxxAir fan
- Open all your cupboard doors | This will help fresh air circulate into all the nooks and crannies
- Pull seat cushions and mattresses away from the walls | Prop them up a little to allow air to circulate around them, keeping them fresh
- Clean the fridge | Make sure it’s dry and keep the door open
- Empty your campervan water system | Empty your fresh and grey water systems and make sure your sink is empty too
- Decommission campervan toilets | If you have a composing toilet, make sure the liquid pot is empty. If you have a portable camping toilet, make sure it is clean and empty. Empty any black tanks too.
- Remove any damp clothes or rags