Prevention is better than cure, so read on for our top tips on how to stop condensation in a van.
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.
Do you live in a van full-time or spend long periods in cold climates? That moisture will play havoc with your health and pride & joy unless you handle it properly.
While there are many things you can do to mop up the moisture, prevention is better than cure.
So how do you stop condensation in a campervan?
What Is Condensation?
Before we can work out how to stop condensation in a van, it’s helpful to understand what it is and its causes.
In simplistic terms, condensation occurs when air, saturated with water vapor, touches something cold, transforming the vapor into liquid.
There are three things at play here worth understanding a little:
- Relative humidity
- Water vapor sources
- Dew point
This term refers to the amount of water vapor air can hold before it becomes saturated.
When the air is saturated, it can’t hold any more water vapor.
Relative humidity is determined by temperature. The warmer it is, the lower the relative humidity and the more water vapor the air can hold.
The more water vapor the air can hold, the less condensation will form.
So to lower relative humidity, we need to increase the temperature.
Water Vapor 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 vapor 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 vapor inside the van.
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 vapor.
Warm air filled with water vapor comes into contact with a cold surface like a window.
This cools the warm air, reducing its ability to hold water vapor.
Once it drops to a certain point, the water vapor 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 vapor.
Why Does Frost Form On The Inside Of The Windscreen?
Have you ever woken up in the morning to find frost inside your windscreen? It makes defrosting a bit of a nightmare but why does this happen?
If the windscreen is really cold – the condensing water vapor freezes, creating a thin film of frost.
How To Stop Condensation In A Van
In reality, stopping condensation in a van is easier said than done.
Taking the above points into consideration, you need to control a few things to stop or at least minimise the condensation in your van.
A well thought out camper van conversion will make for a comfortable, damp-free van.
- Campervan ventilation & airflow
- Controlling moisture in a campervan
- Keeping your camper warm
Campervan Ventilation & Airflow
Excellent campervan ventilation and airflow are the best ways 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 two 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 greatly, as do their features.
They have 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 in exhaust mode to draw out the rising steam whenever we’re cooking.
The other is above the living area, which converts to our bed at night. When we’re cooking, we have this vent drawing air towards the exhausting fan in the kitchen.
We run the vent above the bed in exhaust mode at night, drawing out our breath.
We have 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
Suppose you’ve only one roof vent installed. In that case, you still need another ventilation opening to create the airflow necessary to minimise condensation.
Opening a window in the van is an easy solution.
Our windows are almost permanently open when we’re in it, even with 3 roof vents.
Added wind deflectors protect the interior of the van from rain. They also disguise that the window is open, so opportunistic thieves won’t 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. However, 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 vapor 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 are a few ideas on how you can help reduce the moisture and water vapor you produce in the camper.
Avoid Propane Heaters & Cookers
Burning propane produces a LOT of water vapor – 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 vapor stays in your van.
If you’re considering installing a propane cooker or heater, think about how much time you expect to spend in cold weather conditions where condensation becomes a problem.
With the best will in the world, you’ll need a lot of ventilation to eliminate that amount of water vapor.
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 never cook in your van.
Just try to reduce how much cooking you do inside when it’s cold, if possible.
When practical and dry, use portable barbecues or a camping stove. If you’re staying on a campsite, use their facilities.
When it’s really cold, and you have no choice, up the ventilation and airflow when cooking.
Open the doors and windows and put those roof vents to work. If it’s especially cold, turn on the heater.
You can close up as soon as you’ve stopped cooking so it won’t get too uncomfortable.
Use A Pressure Cooker
Our pressure cooker is one of the van life essentials we think you shouldn’t travel without.
Aside from saving fuel and time, a pressure cooker also emits considerably less water vapor 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 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 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 wet coats and boots are unavoidable when living in the van in winter. So wherever possible, shake off as much moisture before you bring your wet gear into the van.
Better still, if a safe covered area is available, hang your gear 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, we recommend giving it a wide berth if there are signs of leaks (past or present).
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 vapor condenses on it.
A removable tank collects the condensed water so it can be quickly emptied.
We’ve never used a dehumidifier because 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. Still, 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 crucial for avoiding 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 not to mention.
Camper Van Heaters
Keeping your van warm will help to reduce relative humidity and help prevent condensation.
We’ve already mentioned how moist heat from propane heaters produces water vapor, so these aren’t ideal.
Install vented heaters that produce dry heat like Webasto, Espar, or Propex.
The water produced by the combustion is vented out of the van, so it doesn’t add 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 around 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 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 and close it when it’s especially cold.
Air can still circulate to help prevent condensation though the temperature is much lower in the front than in the back.
We do suffer from 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 vapor 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 from reaching the metal walls of the van, so preventing rust.
In reality, installing it so it is completely watertight is almost impossible, and some moisture will get through.
You might think preventing most of the vapor from reaching the metal is better than nothing, but we disagree.
Behind the vapor barrier, air can’t circulate as well as without it. 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 airflow gives any water vapor a far better chance of evaporating than a vapor barrier.
Our advice is to give vapor 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 shoebox 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 are no water producing activities like breathing, cooking, and showering, so the only moisture you need to worry about is what is already in there. And leaks.
If you’re winterizing your camper for storage during the colder months, there are a few things you should do to ensure you don’t return to a mildew infested van come spring.
- Keep at least two vents open | Crack a window an inch or two and leave your roof vents open if you’re undercover 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, 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 composting 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.
Condensation in a van is pretty common in a camper, but it’s important to understand how to prevent it and what you can do to stop it from causing mould and rust in your trusty steed.
With these top tips on how to stop condensation in a van you should be able to keep on top of it and enjoy your van life adventures for years to come!
Don’t let condensation ruin your trip.
Please share your tips for avoiding and getting rid of condensation in a campervan! We would love to hear from you.
Graham is a seasoned marine electrical engineer with two decades of experience designing customized electrical systems for plant machinery and converting campers and overland vehicles. His expertise has led him to author the reputable Campervan Electrics Handbook and become the chief designer of the RV Wiring Design Tool. As a knowledgeable figure in the field, his YouTube channel, blog, Facebook group, and newsletter, offering electrical advice and product reviews, reach more than a million users each year.