Converting a Cargo Van – Mold Preventative Low-VOC Design

This post covers converting a cargo van into a camper for those sensitive to mold and chemical offgassing.

I will focus only on a few key areas:

• Insulating a van in a way that will not go moldy – as metal walls are the trickiest material to insulate because of the condensation factor. Most vans are built wrong and have mold (or will go moldy).
• Low or zero-VOC healthy materials for the walls, flooring, cabinets, and interior.
• A bed platform and keeping the bed dry and mold-free.
• A few appliances that are recommended.

Building a camper that will be both mold-free and chemical-free is tricky!

Keep in mind a cargo van can be anything from a metal box with a bed to a fully decked out camper with a stove, fridge, sink, heater, AC, and even a full bathroom.

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Insulating a Cargo Van to Prevent Mold

The most important aspect of creating a mold-free camper is the insulation.

Here is the key point: no water vapor can enter the wall cavity, in most heating conditions, this means no air can enter behind the insulation.

With exterior metal walls, as soon as you are heating the van to the point where the exterior wall will hit dewpoint, you have a serious risk of condensation and mold in the walls.

So again, to keep it simple, no water vapor and no air can enter the walls if you plan to heat your camper when it’s cold.

Ideally, no air at all should be trapped behind insulation if you want to be extra careful to prevent mold.

If you are in a hot or tropical climate where you don’t heat you will not have this problem of the exterior metal causing condensation.

Rigid Foam Insulation

Camp Like a Girl, a book about converting a van, had a number of flaws and misleading instructions.

The writer uses some XPS and some EPS insulation. XPS is a vapor barrier (meaning no water can pass through 1.5 inches), and EPS is not.

Using XPS foam is one option to insulate your van. XPS or polyiso with foil backing are usually tolerable for most people with MCS.

However, just the foam on its own will not be airtight. You need canned spray foam to fill in the gaps if that is tolerable for you – the thorough system to prevent mold that is working in vans, and was reviewed by a top building science expert, is to fill in the area behind the foam with spray foam and squish it in, leaving no air behind anything.

You need to fill in all the crevices that are not big enough to take rigid foam with spray foam as well.

One part canned spray foam is not chemical-free, but I have found it odorless once cured. You will have to see if it works for you if you are sensitive to chemicals.

Handi-Foam is the safest one, as it is GreenGuard Gold certified. Great Stuff will work for many people. This method involves a lot of canned spray foam.

You can also buy one-part in larger quantities, I am currently testing out this DAP liner to attach foam to walls. They claim this is closed cell foam.

The rigid foam also then needs to be riveted to the frame.

I would not recommend the method in Camp Like a Girl of putting in EPS and not sealing it – this leads to condensation. Because she barely heated the van, and had hot temps in the day, this did dry out in the day and did work in those conditions.

Any foam with air behind can be a problem when heated. Breathable insulation is even more tricky. A few cold days in a row and this will start to be a problem. (I would never use wool insulation in a van, the only exception is very hot climates where you will never be heating the van).

A good way to go about it – if it’s warm enough – is to sleep in the van empty and slowly work on insulating and building it out. The other option is to get it all done and then wait for it to offgas. 

Rigid Foam in the Bed

Some have used insulation in the bed platform to keep the bed warm. I would be concerned here with flame retardants in the foam, and putting a bed on a flat surface is a no-no for mold.

In the bed section, I discuss how to use insulation under the mattress without causing moisture and mold.

Spray Foam Insulation

Spray Foam without any rigid foam is, in theory, your safest bet for preventing mold. The foam will get into every crevice and form an airtight layer that will prevent all moisture from getting into the walls. 

Two-part spray foams are much riskier than the one part canned spray foam discussed above.

The best spray foams are Heatlock Soy line at Demilic and Icynene Proseal (both GreenGuard Gold) (closed cell). Both are polyurethane foams, from reputable companies that are usually easy to source.

A reputable and very experienced installer is more important than the brand, as that is where the process goes wrong and can cause it to fail to cure properly. This causes major offgassing that may not stop.

The DIY kits for this type of spray foam are a definite no. And it must be closed-cell spray foam, which is a vapor barrier. 

I might recommend these to healthy people who are set on spray foam. I don’t usually recommend them to people with MCS because of the possibility of prolonged offgassing.

The companies say they do not offgas, but I seen many stories from moderately sensitive people that this does offgas noticeably in buildings. A small sample may air out quickly, but test this in a building before using it.

At least two years (if this is installed correctly) may need to be scheduled into offgas this for the moderately sensitive. If not installed correctly it’s a goner, you’re going to be scraping out the whole thing. 

If you are mold sensitive but not chemically sensitive you could consider this in a van. I have heard though, both in Airstreams and in vans, stories of spray foam pushing out the frame in areas causing problems. A skilled installer may be able to clarify why this happens.

Airstream as well as Winnebago, have moved away from two-part spray foam due to problems. 

Wall and Ceiling Materials 

Metal is your safest bet unless you are putting the plastic covers back on.

If you do put the plastic covers back on, caulk around the seams to prevent moisture from going into the walls. 

If you want your interior walls to be another vapor barrier layer, the metal or plastic should be used and caulked airtight.

If tin/aluminum tiles are used it’s best that behind them is airtight (though if you have enough insulation this might not be necessary). If you don’t have enough insulation, you could have condensation behind the wall cover. 

Some folks are putting canned spray foam behind the tin tiles for an extra layer of air sealing.

I have also seen gaskets with solid silicone sheets used to make the walls airtight.

In a cargo van or trailer, instead of using metal walls, my preference would be to keep the walls as simple as possible so that you can open them up to check on problems.

You may want to use plastic sheets, or could simply tack up and cover the foam with the material of your choice:

• Silicone “leather” which comes in rolls
• Polyurethane leather
• Polyester fabric murals
• The grey side of house wrap (which looks cool)
• Painted foil or metal walls with AFM metal paint
• Polyethylene wall tiles (if you can tolerate the glue)
• Seal everything with shellac and then paint directly over XPS

There is no reason to use PVC, the most toxic plastic, in areas like the ceiling tiles. But real tin ceiling tiles could be used as a non-toxic alternative which also adds a fun look to your camper. 

While The Vanual, a popular van conversion, looks very pretty with its wooden ceiling, I would avoid plywood as walls, ceiling or subflooring. There are just too many points where the wood hits the metal.

If you are intent on getting this look, you would have to have lots of insulation at all the metal ribs to make sure dewpoint would never be hit there.

If that is possible, then you could use plywood with strips of wood over it to get the look in The Vanual. Use a wood that can take high humidity. 

Floor Materials for a Van

I wouldn’t use wood to raise the floor joists as the wood right against the metal is usually a recipe for condensation and mold.

Rigid foam may be your best bet for floors to solve the thermal bridging there, with the same system of canned spray foam above and riveting used to make it 100% airtight. 

Flooring materials that could be considered include:

1. 1. Metal sheets, which could be painted with AFM Metal Primer with different designs for a pretty effect, or covered with rugs.

1. 2. Marmoleum. Be careful here as Marmoleum sheet (the rolls) have jute backing. Use plenty of insulation underneath and an underlayment with a thermal break to prevent condensation. The Marmoleum tile format has a polyester backing.

• 3. Plastics: Hard plastic sheets like plexiglass, rolls of silicone, EVA mats.

• 4. Plastic-based flooring: plastic rugs, or luxury vinyl planks (LVP). Both are extremely low in offgassing, though still could be bothersome for some folks. You could also use polyurethane sheet flooring which is practically odourless or other similar flooring products listed here.

• 5. Garage flooring: super-duper easy to install. The brand is Europe is Bergo but in the US there are a number of them on Amazon like GarageTrac.

• 6. Wood Flooring: Engineered wood flooring or laminate if you are sure you have enough insulation underneath to prevent condensation from forming under the wood, a thermal break, and that the wood can withstand the humidity in your area. 

Subfloor

If you are concerned about denting, use hard plastic sheets (plexiglass) or metal sheets. MgO board has worked for some but is prone to cracking (and is permeable).

Interior Structures: Bed, Cabinets

Bed Platform – Non Breathable Set up

Camp Like a Girl and The Vanual used plywood for their bed bases. If it’s softwood plywood it needs a little time to offgas formaldehyde.

The other option is formaldehyde-free Purebond plywood (but I wouldn’t use a non-moisture resistant wood species in a van or small trailer if you will have high humidity).

Purebond does come in moisture-resistant species, even cedar. The glue is not made to withstand high humidity but should work in many vans.

It also doesn’t let the mattress breath. Mattresses are very susceptible to becoming damp in campers. Even in a house, one should never put a regular breathable bed on a solid surface.

To prevent this moisture transfer there are two strategies to use on a platform.

One, cover the mattress with a waterproof protector before installing it in on the camper platform.

The other option is to use a bed that doesn’t transfer moisture and doesn’t mold, like this well-tolerated TPU air mattress (takes only a couple days to offgas to my standards).

An air mattress won’t keep you warm. I use the thickest Thermarest which is more comfortable than an air mattress for me (took a week or so to offgas enough for me) and I put a waterproof cover on it.

If you want to add insulation, I would add cork sheets (Thermacork brand), this is healthier than foam because of the flame retardants in foam.

Bed Slats – Breathable Option

Another strategy is to have the bed base made of planks/slats that allowed some airflow. With this strategy, you may be able to use a bed that is not covered in plastic or isn’t an air mattress.

Either way, the bed should be flipped and checked often for dampness, especially if you cook or shower inside.

I would use bedding made of polyester, wool, or silk, (and not cotton) because these are more resistant to the high humidity in vans. 

How to keep warm in a bare metal van 

Since insulation is so tricky, many mold avoiders keep the van bare. The best way to stay warm is to have insulation below you and above you.

Extra protection from the elements would be to add a canopy over the bed and a heat source.

Insulate Under You

I like the method of adding insulation below you. There are a few ways.

A thick Thermarest like the Mondo King provides insulation under you. Or just a slab of polyurethane foam (I have used both).

But I like the idea of adding a layer of insulation below that. I like Thermacork, a pure cork insulation. You could use foam: EPS polystyrene (the kind made for packing or crafts should not have flame retardant), it is also a little bit breathable.

You then add your waterproof layer to your bed. Then add a biomat or heating blanket.

Above you, you have your sleeping bag/blanket.

Ideally for warmth, if you can tolerate it, your heating blanket is actually inside the sleeping bag. Heating blankets can run off solar. The smaller ones are only 60 watts but will keep you really warm if they are inside a sleeping bag.

Stay Even Warmer by Creating a Canopy or Tent Inside

You can go one step further to stay warm and create a canopy or use a raised up tent inside the van. Anything to create a canopy – using the fabric of your choosing (as long as you have enough air) will keep this even warmer.

If the area inside my tent or canopy is large enough for this to be safe – I add a tiny heater. I use this tiny Honeywell heater in all my small structures. Be careful!! you need to take a lot of precautions when adding a heater in a small space. Make sure you have enough clearance.

Cabinets

For cabinets, if you do use plywood, go for a formaldehyde-free plywood like Purebond (moisture resistant wood types only – the glues might not hold up to extreme humidity), offgassed APA exterior plywood, or use solid wood (which may warp in high humidity). I much prefer metal cabinets. You could also use polypropylene cabinets.

Ventilation in a Van

You need fans that move air out – one above the shower if you have one, and one in the general space.

My CampLite trailer had two fans and we still have problems just with cooking humidity making the mattress wet.

The standard camper fans are called Fan-tastic.

Van Appliances

The Vanual has some cool tips for solar power, wiring, and appliances.

If you want to go off-grid you will need solar. And you generally you will need to tolerate a fuel stove.

The Vanual and other van owners speak highly of Goal Zero solar systems because of how easy it is to install. Some people just use the solar charger outdoors.

The other option is to wire the van to plug into a campground plug (or modify to plug into a house), this would allow you to cook on an electric hotplate and would allow an electric heater.

Right now I use an Instant Pot to cook everything and I release the steam outside. This is a really good way to reduce moisture in a van or little trailer. You can cook almost anything in that.

Using an electric blanket is a good heating option to save energy. The best kinds are the large ones with the 10 hour shut off time to keep you warm all night. If you don’t tolerate those, a biomat may be better tolerated.

I would not use the stand-alone propane heaters that go inside as they will not be safe for those with MCS.

For cooking, if you are off the grid you will need to burn some fuel to cook. Cooking outdoors is safer. Alcohol burning stoves are safer than propane. Though this won’t be tolerable for many.

For a fridge, I would go with a 3-way fridge that can run on propane solar or AC electricity. Unlike in most trailers, propane is stored inside in vans, so this could become a problem for some.

The Vanual recommends running this fridge on solar or the car battery.

Here is an example of a fully decked out custom van made for someone with MCS (you would want to see how the construction was done if you wanted to copy or buy this one).

Choosing a Van

Sensitive folks have reported liking the big 4: Nissan NV, Dodge Ram Promasters, Ford Transits, and Mercedes Sprinters.

Some have found that Chevy and GMC were not as good for people with chemical sensitivities.

Anyone sensitive should check out a number of brands. And of course, there are differences between the brands in terms of size and height and all kinds of things.

Corinne Segura is a Building Biologist with 8 years of experience helping others create healthy homes.

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Carl Grimes, Certified Indoor Environmental Consultant, reviewed the mold preventative insulation system for vans. Extreme mold avoiders are using this system with success.