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Wet-Weather Kit for Van Life

Why a van is the wettest place you will ever live

A van is a metal box with a large glazing area, thin insulation by house standards, and an occupancy density that no building would permit. Two people in 3.5 m3 of air is roughly 0.57 people per cubic metre; a typical bedroom runs at about 0.05. Every surface is either glass or a thermal bridge to the outside, and both are the coldest surfaces in the space, which is exactly where water vapour goes to condense.

Then there is the doorway. In a house you walk through a hall, kick off your shoes and hang your coat. In a van you step from rain directly into the living space, usually onto the same floor you sleep above. The first 30 seconds after opening the side door on a wet day decide how much water ends up in the bed, and almost nobody plans for them.

The result is that van dwellers who have never had a leak wake up to wet windows, damp bedding and a smell in the soft furnishings by the second week of autumn. None of that is a bag failure or a seal failure. It is condensation, and it is solved with airflow and separation, which is what the kit below is built to do.

The moisture budget: where the litres come from

Write the water down before you buy anything. Two adults exhale roughly 0.35 litres each over eight hours of sleep. Cooking on LPG is a bigger source than most people expect: burning 100 grams of propane produces about 164 grams of water as a combustion product, so a week of cooking two hot meals a day contributes close to 2.3 litres. Add showering if the van has one, add drying kit, and the daily total lands between 1.5 and 3 litres.

Add the column and it is obvious why a 500 g desiccant tub is a rounding error. That tub absorbs perhaps 150 grams before it is saturated, against a daily load of 1.5 litres, so it buys you a few hours and a false sense of progress. Airflow is the only control that scales, and it is the one worth spending money on.

Dew point: why the windows go first

Condensation happens on the coldest surface once it falls below the dew point of the air. At 20 °C and 60 per cent relative humidity the dew point is about 12.2 °C; at 70 per cent it rises to 14.4 °C. A single-glazed side window with 2 °C air outside and no internal insulation will sit at 6 to 9 °C on its inner face, so it is below the dew point for most of a cold night and it runs with water.

The fix has two halves: raise the surface temperature and lower the humidity. Insulated internal window covers do the first, lifting the inner face by 5 to 8 °C and often enough to stop the run entirely. Ventilation does the second, and it is the half people resist because it feels like letting heat out. It does let heat out, at a cost of roughly 30 to 60 watts for a modest continuous extract, which is less than a 2 kW heater spends in ninety seconds.

Ventilation maths: air changes per hour

Size the fan by air changes rather than by catalogue description. A 3.5 m3 cabin needs about 8 to 12 air changes per hour while cooking or drying kit, and 2 to 4 as a continuous baseline. That is 30 to 60 m3/h running and about 10 m3/h baseline, which is well inside what a single 12 V roof fan rated at 100 m3/h can deliver on medium against a small amount of back pressure.

The detail that matters is make-up air. An extract fan cannot move air out of a sealed box, so there must be a low-level inlet of comparable area, usually a floor vent or a cracked window on the leeward side. Without it, a 100 m3/h fan delivers perhaps 35 m3/h in practice and the humidity barely moves.

A diesel heater changes the numbers in your favour without adding moisture, because it is a sealed combustion unit. Raising the cabin from 14 °C to 20 °C at constant water content drops relative humidity from about 75 per cent to 52 per cent, which is the difference between a wet window and a dry one. Run heat and extract together for 20 minutes after cooking and the cabin dries faster than with either alone.

The door-side wet zone

The most valuable square metre in a wet-weather van is the 600 mm inside the sliding door. Everything that happens there decides whether water travels further into the vehicle. The rule is the 30-second rule: within half a minute of closing the door, wet outer layers are off, boots are in a bag, and the floor is wiped. After 30 seconds, water has already spread.

1. Brush or stamp water off boots on the step before stepping in.
2. Outer shell straight into the 10 L boot bag, never onto the floor.
3. Boots into a 10 L bag with the mouth open, standing on a ribbed mat.
4. Wipe the floor mat with a small squeegee or a microfibre cloth.
5. Hang the jacket on the rear door hook with at least 100 mm of air gap.
6. Close the door and run the roof vent on boost for ten minutes.

The mat matters more than people expect. A ribbed rubber mat with a raised lip holds about 0.5 litres in its channels and stops it spreading to the ply floor, where it will find a seam and start a rot problem you will not see for a year. A flat carpet mat holds nothing and dries slowly, which is worse than no mat at all.

Staging wet kit: three bag sizes, three positions

Wet kit needs three separate destinations, because a wetsuit, a pair of boots and a damp jacket have completely different drying times and odour profiles. Mixing them in one bag guarantees that the fastest-drying item is re-wetted by the slowest, and that the whole bag smells by day three.

Position is as important as bag size. Anything that is drying needs airflow on both faces, and a bag sitting flat on a floor delivers airflow to one face only. Hang it, prop the mouth open with a rolled towel, or stand it upright against a vent. A 20 L bag with a wetsuit in it will dry in about 12 hours hung and will still be damp after 36 hours lying flat.

Drying without a tumble dryer

Nobody has a tumble dryer in a van, so drying is a function of airflow, surface area and temperature. A 12 V fan moving 100 m3/h across a hung jacket removes roughly 200 grams of water per hour at 15 °C and 60 per cent humidity; the same jacket lying on a bed manages perhaps 60 grams. Surface area and moving air beat heat, which is why a cold van with good airflow dries faster than a warm one with none.

The practical setup is a line over the cab or across the rear doors, with each item hanging freely and at least 100 mm between neighbours, plus a fan aimed along the line rather than at it. Add a 2 kW heater on low for 30 minutes after the wettest items go up, not to dry them directly but to lower the relative humidity so the air can hold more water.

One caution about hanging near a heater outlet. Diesel heater air leaves the outlet at 80 to 110 °C, and a TPU bag 100 mm away from that outlet will exceed its comfortable service range within the hour. Keep bags at least 400 mm from any heater outlet and never drape anything over the unit, which is a fire risk as well as a fabric one.

Rain gear, sports kit and the garage

The garage, the space under a fixed bed, is the natural home for wet outdoor kit because it is usually the coldest and best-ventilated part of the vehicle and it is separated from the sleeping area by a bulkhead. That separation is the whole point: a wetsuit stored under the bed does not humidify the bedding. Keep the garage kit in a 40L bag with welded seams so that nothing seeps into the ply.

Sports kit brings specific problems. A surfboard bag carries salt and sand, a bike kit carries chain oil, and both should never meet the dry clothing store. Give each its own bag, rinse salt off with 1 litre of fresh water before storage, and accept that this corner of the van will always be the damp one. That is fine, as long as it is the only damp one.

If the van doubles as a base for winter sports, the load changes again. Ski boots carry 0.3 litres of melt water each and the liners take 24 hours to dry at 15 °C. A 20 L bag per pair, opened in the garage with the liners pulled out, is the only arrangement that works, and a small 12 V boot dryer running at 25 watts overnight is worth more than any bag.

Bedding and the sleep system

The bed is the thing you are protecting. A duvet that picks up 200 grams of water over a week feels damp, weighs more and loses loft, and it is the hardest item in a van to dry because it is bulky and usually lies flat. Two habits protect it: open the bed to air for an hour each morning before making it up, and keep a 40L bag for spare bedding that is never opened except to swap.

Memory foam and closed-cell mattresses are unaffected by humidity, but the ply beneath them is not. Condensation forms under a mattress that sits directly on a cold panel, and the classic result is a black patch of mould under the bed after one winter. Fix it with a slatted or ventilated base with a 20 mm air gap, and lift the mattress once a week to check.

Cold weather and frozen kit

Below freezing the problem inverts: instead of too much water in the air, you get water freezing where you do not want it. A water container in the garage drops below zero overnight, a wet bag left outside the rear door becomes a solid block, and a roll-top closure stiffens enough that three folds become hard work at minus 8 °C.

TPU handles this better than PVC, staying workable to about minus 30 °C, but the closure still needs care. Roll the bag loosely, do not force a stiff fold, and keep closures inside the heated envelope overnight. Water containers go in the cabin, not the garage, and anything with liquid in it moves inside below minus 3 °C.

Cold also changes how you ventilate. Cold air holds almost no moisture, so extracting it and warming it is the single most effective drying action available in winter: air at 2 °C and 80 per cent humidity warmed to 20 °C arrives at about 21 per cent relative humidity. That is why a winter van with a good fan and a heater is often drier than a summer one with the windows shut.

Mould, health and when it stops being cosmetic

Sustained relative humidity above 70 per cent on a cold organic surface is where mould germinates, and in a van the organic surfaces are ply, fabric trim, carpet and any paper or clothing stored against a panel. Damp and mould in buildings is treated as a health issue rather than a maintenance one, and the EPA guidance on moisture and mould indoors is the standard reference for why that is.

The health effects are real enough to plan around. Respiratory symptoms, irritation and allergic responses are all associated with indoor dampness, and the CDC publishes guidance on mould exposure and cleanup that applies just as well to a vehicle interior as to a house. If you find more than about 0.1 m2 of growth, treat it as a remediation job, not a wipe-down.

Practically, that means a weekly inspection. Lift the mattress, pull the garage bags out, feel the ply under the bed and look at the window rubbers. Ten minutes a week finds every problem while it is still a cloth-and-vinegar job rather than a rebuild.

The daily and weekly routine

1. Morning: extract on boost for ten minutes, windows wiped with a squeegee.
2. Bed opened and aired for one hour before it is made up.
3. Cooking with a lid on the pan and the vent above the hob open.
4. Door-side routine applied within 30 seconds of every entry in rain.
5. Wet kit hung with 100 mm gaps and a fan aimed along the line.
6. Evening: heater plus extract for 20 minutes, then vent on trickle overnight.
7. Weekly: mattress lifted, garage emptied, ply inspected, bags rinsed and dried.

The overnight setting is the one that takes longest to get right, because it changes with the weather. On a mild damp night, trickle ventilation at about 10 m3/h plus insulated window covers is enough. On a freezing clear night, more airflow and slightly more heat works better. Watch the windows rather than the thermometer: dry glass in the morning means the setting was right.

Kit list and the sizing checklist

• Buy one 40L, one 20L and one 10L before buying anything else; those three cover every job.
• Confirm welded seams, because a garage bag sits in water by design.
• Choose TPU over PVC if the van sees winter, and check the cold-crack figure.
• Keep every drying bag at least 400 mm from a diesel heater outlet.
• Colour code the bags so wet and dry are never confused in the dark.
• Match bag size to the garage, not to the shop: measure the aperture first.

Operators building rental fleets or conversion packages run into the same five decisions at scale: volume, film thickness, closure type, colour and hard points. Our production partner has produced waterproof bags since 2014 in an SGS-verified 4,950 m2 facility, with a 500-piece minimum and sampling in 6 to 10 working days, and van packages now make up a steady share of that work.

Finish by matching the kit to the climate you actually live in, because a setup tuned for a wet Scottish winter will over-ventilate in a dry Spanish one. Our climate matching guide covers that choice, and the condensation guide explains what is happening when a sealed bag still ends up wet inside. For the drying side, the racks and airflow notes go further on airflow geometry, and the slush protection guide covers the shoulder season when melt water is worse than rain. Our TPU waterproof backpack range covers the day bag, and the full blog index carries the rest of the series.