Condensation is a common phenomenon that occurs when warm moist air meets a cold surface. Condensation occurs because the volume of water in the air increases. Moisture-laden air can quickly cool down when it comes into contact with a cold surface, such as a window, and when that happens it is no longer able to hold the moisture. As a result, the vapour turns into liquid and accumulates on the surface, leading to the buildup of moisture inside the van.
In the case of vans, this can lead to a buildup of moisture on the windows, walls, or roof. The most significant issue with condensation in a van arises when it’s cold outside and you’re trying to stay warm.
This is important because water in a campervan can lead to all sorts of problems, from mould, to rotting to rust.
This article will break down what condensation is, how to know if you have it, and what you can do to prevent it. In the next article we’ll dive much deeper into ventilation, and how to install roof vents and (eventually) windows in your campervan.
But first, some science:
What is condensation?
There are three primary factors that cause condensation: relative humidity, water vapour sources, and dew point.
Relative humidity is the amount of water vapour in the air compared to the maximum amount it can hold at a given temperature. The relative humidity in a van can be influenced by several factors such as cooking, washing, and breathing. When the humidity level (amount of water in the air) is high, the chances of condensation increase. Temperature plays an important role in relative humidity, increasing the temperature inside the van can help reduce the relative humidity and prevent condensation.
Water vapour source; human activities inside a van can contribute to the amount of water vapour in the air, which can increase the likelihood of condensation.
And Dew point, which is the temperature at which water vapour in the air begins to condense into liquid. When warm air filled with water vapour cools down to its dew point, the water vapour in the air condenses into liquid form.
What causes Condensation in a campervan?
The main cause of condensation in a campervan or motorhome is the introduction of moisture into the warm environment of the vehicle. Various factors can contribute to the moisture in the air, which ultimately leads to condensation settling on any surface that is colder than the dew point. Here are some common culprits that can increase the absolute humidity level inside the van*:
Overnight breathing and body heat: at rest, a person can release about 50 ml of water per hour, which amounts to 400 ml overnight. During the day, breathing (more heavily than at night) releases roughly 2l of water per person.
Cooking: more or less, about 250 ml of water is evaporated when cooking a meal.
Wet clothing left to dry: can release around 250 ml of water per day.
Showering: taking a 5-minute shower can release up to 250 ml of water into the air.
Washing-up in hot water: can release around 100 ml of water per day.
Drying stuff: drying dishes, dish cloth, boots, jacket, etc. can add another 250+ ml of water per day.
Water ingress: any water leaks that lead to damp floors, walls, and ceilings can contribute to increased humidity in the air.
All of these activities increase the absolute humidity level by evaporating water into the air, and can lead to condensation if the moisture becomes trapped and settles on any surface that is colder than the dew point, unless there is circulating air to move it around and take the moisture-laden air away.
*Please note that these values can vary depending on factors such as the size of the vehicle, the temperature, and the humidity levels outside.
Signs of Condensation in a Campervan
Signs of condensation in your campervan are easy to spot. The most obvious sign is seeing moisture on your windows, ranging from a slight mist to heavy droplets/ water trails, depending on the amount of moisture in the air. You may also feel that your bedding or clothes are slightly damp, even though they were dry when you went to bed.
If the condensation is persistent, it can lead to mould growth, particularly in areas where air circulation is limited, such as under your mattress. You can clean this mould off with a cleaner but it will continue to return until the root cause of the problem is addressed.
If it’s any worse; mould, black marks, or damp patches along seams and joints in walls and ceilings, accompanied by a musty odour, may indicate that you need a damp check, for which you will need a damp metre. Any more than 20% damp and you will need to take some time to really investigate the issue.
Why is Condensation such a big deal?
Condensation in a campervan or motorhome is not just a minor annoyance that can be dealt with when it comes up.
Unchecked moisture can lead to mould, as we’ve seen. That can – on the low end of the scale – make your van a less enjoyable environment to be in and – on the higher end of the scale – make you sick.
If you have any woodwork in your campervan, the moisture could lead to the wood rotting.
Same goes for any fabrics, causing stains and pretty foul odours that can be hard to remove. Here’s the big one though, if certain insulation materials get wet, and since you probably can’t see them through the walls, mould can form without your knowledge.
Anywhere that wet insulation touches your body panels will turn it to rust that can eat your van from the inside out, with you none the wiser until it’s too late.
Condensation Prevention
As condensation is formed when moist air hits a cold surface then to reduce condensation in the van we must try to either reduce the amount of water vapour in the air, remove the air completely, or warm up the cold air and surfaces.
Vapour Barrier (or sound deadening material): Adding a vapour barrier or sound deadening material can help prevent condensation by minimising the surfaces where moisture can accumulate. Cover all exposed metal on the inside of the van to achieve the best results.
Proper insulation: Proper insulation installation during your van build can be a major life-saver. The key point with insulation is getting it flush with the van’s metal surfaces. There are many types of insulation to choose from, and we have a guide for insulation.
Good ventilation: Maintaining good ventilation is crucial in preventing moisture inside the van. Pulling the moist air out of your van and replacing it with fresh air from outside while keeping good airflow is one of the best tactics for preventing moisture inside the van. Installing a good-quality van roof fan is a great way to pull moist air out of your van. Here’s our take on ventilation and installing vents.
Heaters: Specifically, an externally vented heater. Propane heaters are easy to install and do a great job of heating the space, but they produce a lot of moisture. Externally vented heaters are designed to burn out the moisture before bringing the air into the van, preventing extra water vapour. If you want to, you can jump straight to our heating your van section.
Dehumidifiers: While dehumidifiers can be useful for controlling moisture, they are not a complete solution to condensation, especially when it gets too cold outside. They work by removing moisture from the air, but if the temperature drops below a certain point, condensation will still occur.
If you want the most thorough method, it’s best to try to combine insulation, ventilation, and heating to keep the interior temperature above the dew point temperature.
Our tips for reducing Condensation whilst on the road.
This isn’t really linked to Van conversion, per say, but we’ve learned this since living in a van and so happy to share it with you:
- Keep Your Motorhome Warm: One of the most effective ways to prevent condensation in a van is to keep the inside of the van warm. This can be achieved by running your van’s heating system or using a portable heater. By maintaining a warm and comfortable temperature, you can prevent the air from cooling down enough to cause condensation.
- Open a Window: Opening a window is another effective way to reduce humidity and prevent condensation. Fresh air will circulate throughout the van, and this will help to keep the air dry.
- Open windows and doors while showering: Fully open roof lights or windows while showering and leave them open for 30 minutes after finishing to help reduce excess moisture. Read about installing windows here.
- Cook outside: Take your moisture outside, you are living #vanlife, after all. Here are some cooking options for you.
- Keep the lid on: If you have to cook inside the campervan, keeping the pan lid on while cooking helps to remove (some) steam and moisture from the air.
- Don’t block air vents: Air vents located under campervan furniture should not be blocked up as they are a vital source of ventilation. Make sure furniture is arranged in a way that allows air to flow freely.
- Keep the Roof Vent Open: A roof vent is a great way to keep the air circulating and reduce condensation in your van. Even a small opening can help create cross-flow ventilation, allowing fresh air to enter and wet air to escape.
- Install a powered vent: Installing an extractor fan or vent is another effective way to remove excess moisture from the air. These fans can help remove moisture from the air after taking a shower or cooking, which are the two main activities that generate a lot of moisture in a van.
- Use insulated window coverings: Insulated window coverings help to keep the heat in and prevent the cold air from coming in contact with the window. These coverings come in many different materials, including foil, bubble wrap, and quilted fabrics. Cab blinds can also be helpful in preventing warm air from reaching the windscreen.
- Invest in a dehumidifier: Dehumidifiers work by removing excess moisture from the air, leaving the air dry and free of condensation. There are many different types of dehumidifiers on the market, including 12v and rechargeable models.
- Don’t invest in a dehumidifier: Dehumidifying crystals or placing a few bowls of salt around the van can act as a homemade moisture absorber. The crystals and salt will absorb excess moisture from the air and can be easily replaced once it becomes saturated.
- Clean on a breezy day: Cleaning the interior of the van on a breezy day with windows and roof lights open can help dry out any excess moisture. It’s best to avoid cleaning on a damp or rainy day as this can add moisture to the air.
- Avoid drying clothes indoors: Drying clothes indoors increases the amount of moisture in the air. Instead, hang clothes outside and if you must dry clothes inside, try keeping it all to the cab/ garage.
- Use kitchen roll: Using kitchen roll to wipe down the windows in the morning can help to remove any condensation that has built up. This is a quick and easy way to keep your windows clear and free of condensation build up on the panels below.
- Use a window vac: A window vac can be a great tool for quickly and easily removing any condensation from your windows in the morning. Bourgie.
- Ensure dry storage: Before putting away any items or clothing, make sure they are thoroughly dry. Moisture trapped in storage containers can contribute to condensation in the van, or mould in the boxes.
- Manage condensation in wardrobes: Store clothes and other items in wardrobes so that they aren’t too close together, ensure they are dry before hanging them up, and consider using dehumidifying crystals to absorb excess moisture.
- Keep wet pets outside: Controversial, because we love our animals. But, wet pets can contribute to excess moisture in the air, so it’s best to keep them outside until they’ve dried off (if you can).
- Turn cushions and mattresses: Regularly turning cushions and mattresses can help with air circulation and prevent excess moisture from being absorbed into one spot.
- Check for leaks, often: Check under the bathroom and kitchen sink for any leaking taps and get them repaired to prevent excess moisture.
Bonus material:
Why Does Condensation Form On The Outside of Your Van?
Condensation can form on the outside of your van when the outside air is warm and humid, and the van’s surface is cold. When warm, moist air comes into contact with a cold surface, the air temperature drops, causing the moisture in the air to condense into liquid form. This is why dew forms on grass and other surfaces early in the morning when the temperature drops overnight, and the ground and other surfaces cool down.
Similarly, when the surface of your van is cold, and the air outside is humid, the moisture in the air can condense on the van’s surface, leading to the formation of condensation. This can happen when the van is parked outside on a warm, humid day, and the air inside the van is relatively cool. The cold surfaces of the van, such as the windows and metal body, attract moisture from the surrounding air, causing condensation to form on the outside.
Why does frost form on the inside of the windscreen?
Frost can form on the inside of the windscreen when warm, moist air inside the van comes into contact with the cold windscreen. The moisture in the air condenses on the windscreen, forming droplets, and if the temperature drops below freezing, the droplets can freeze, forming frost.
This can happen when the van is parked in a cold place, and the inside air is warm and humid. When the warm air comes into contact with the cold windscreen, the moisture in the air condenses and freezes, forming frost on the inside of the windscreen. This can make it difficult to see out of the windscreen and can be dangerous when driving.
Now we know a bit more about condensation. There’s more to come on the website about heating the van, and installing windows and ventilation. It’s about time to start the build, so let’s cut some holes and get the air moving in our next article.