Condensation is the single biggest annoyance of van life in the UK. Every van gets it — the windows stream with water, bedding feels damp, and if you ignore it, mould grows in your cupboards and behind your plywood panels.
You can't eliminate condensation entirely (the physics doesn't work that way), but you can reduce it to a manageable level. Here's how, based on what actually works in UK vans.
Why Vans Get Condensation
Condensation happens when warm, moist air hits a cold surface. Your van's skin (metal roof, single-glazed windows) is thin and cold. Your breath, cooking, and wet clothes produce warm, moist air. The two meet on the windows and walls.
In a house, you have central heating, double glazing, cavity wall insulation, and an extractor fan. In a van, you have a diesel heater that cycles on and off and a window that's a single sheet of glass.
The Fundamentals
Before buying dehumidifiers and anti-condensation paint, fix the basics:
Ventilation
Permanent ventilation is the single most effective intervention. Every van needs:
- A roof vent (Maxxair or Fiamma) — extractor mode pulls moisture out. Run it on low continuously during winter, even overnight. The power draw is negligible (0.5-1A on low).
- Cracked windows — leave a window open 5-10mm when you're in the van. The Fiamma Secure window rafter (£15-20) lets you crack a window open without leaving a security gap.
- Floor-level vent — many vans have a floor vent in the garage area. Cold air in at floor level pushes warm moist air up and out the roof vent. This is the "stack effect" and it works without any power.
Heating
A diesel heater running at a constant low temperature (12-15°C) produces less condensation than a heater that runs hot for 30 minutes then shuts off for 3 hours. The constant low heat keeps the van's surfaces above the dew point. The cycling hot/cold pattern makes condensation worse.
Cooking
Cooking produces more moisture than anything else. A pan of pasta boiling for 10 minutes releases 300-500ml of water vapour into the air. That has to go somewhere.
What helps:
- Cook with the roof vent running on high
- Use a lid on every pan (cuts moisture release by 80%)
- Consider cooking outside (under an awning or tarp) in winter
- An induction hob produces less moisture than gas (no combustion byproducts)
Products That Work
Moisture Absorbers
| Product | Type | Cost | How Long It Lasts | Effectiveness |
|---|---|---|---|---|
| Kilrock Damp Trap | Passive (calcium chloride) | £3-5 | 4-8 weeks | Moderate — absorbs 200-300ml before saturating |
| UniBond Aero 360 | Passive (refillable) | £10-15 | 8-12 weeks | Moderate — better coverage |
| De'Longhi DEX214F | Electric dehumidifier | £120-150 | Permanent | High — 500ml/day, but uses 200W continuously |
The problem with passive absorbers: People think one Kilrock damp trap in the middle of the van solves condensation. It doesn't. A moisture absorber absorbs about 200ml before it's done. A single night's breathing produces 300-500ml of moisture. You need the fundamentals (ventilation + heat), not just a tub of calcium chloride.
When to use passive absorbers: Inside cupboards and storage boxes where air circulation is poor. A small damp trap in your clothes cupboard prevents mould on your jumpers.
The Karcher Window Vac
The Karcher WV1 or WV2 (or generic equivalent, £40-70) is a hand-held device that vacuums water off windows. Wipe your windows in the morning with a dry cloth and then vacuum the excess with the Karcher. It sounds trivial but it keeps your window seals dry and prevents the water from running down into your door pockets and causing mould.
Alternative: A proper silicone window squeegee (like hairdressers use, £5) and a microfibre cloth. Same result, costs less.
Anti-Condensation Paint
Ronseal Anti-Condensation Paint (£25-30 for 2.5L) contains microscopic beads that create an insulating layer. It's designed for garages and sheds but works on van walls. One coat on the metal ceiling panels reduces condensation by about 30%.
Important: It only works on metal surfaces (the ceiling and walls above the lining). It does nothing for windows.
Thermal Window Covers
Internal window covers (like the ones from Campervan Covers UK or Van Windows) use a layer of insulating foam with a reflective surface. They reduce heat loss through the cab windows by 60-70%, which means the window surface stays warmer and condensation is less likely to form.
Cost: £8-15 per window (cab windscreen, side windows, rear doors). Get the silver-backed ones — they reflect heat back into the van.
What Doesn't Work
- Candles — a candle produces more water vapour than it absorbs. "Candle dehumidifiers" are a scam.
- Cat litter in a tray — silica crystal cat litter absorbs some moisture, far less than a dedicated damp trap. It smells like a litter tray after a week.
- Rice — absorbs almost nothing in van conditions. Stick to actual dehumidifiers.
- Cracking a window 1mm — that's not enough. You need 5-10mm gap for meaningful air exchange.
Winter Mould Prevention
Mould in a van is a health hazard (respiratory issues, allergies, asthma triggers). It grows in dark, warm, damp spaces — i.e., inside your cupboards.
| Area | Risk | Prevention |
|---|---|---|
| Cupboard under sink | High (damp from pipes) | Leave cupboard doors open when possible |
| Bed base storage | Medium (mattress sweats) | Slatted bed base (not solid plywood) for airflow |
| Clothes cupboard | High (damp clothes) | Damp trap inside, don't store damp clothes |
| Behind wall panels | Low (if properly insulated) | Vapour barrier between insulation and panel |
| Floor under bed | Medium (cold spot) | Elevated bed with airflow underneath |
Once a week in winter: Open all cupboards, lift the mattress, open the rear doors, and run the roof vent on high for 30 minutes. This flushes out the trapped moist air that accumulates behind closed doors.
The Morning Routine
Every van lifer in the UK develops a morning condensation routine:
- Wake up. The windows are wet. Don't ignore it.
- Wipe all windows with a microfibre cloth. Wring the cloth into a sink/bottle.
- Vacuum the window seals with a Karcher or wipe dry with a second cloth.
- Open the roof vent. Crack a window. Let the van air out for 10 minutes while you make coffee.
- Wipe the metal walls above the window line — they'll be damp too, even if you can't see it.
- Check the damp traps in your cupboards. Replace if saturated.
This takes 5 minutes. Skipping it for a week leads to mould.
The Bottom Line
Condensation in a van is a ventilation problem, not a product problem. A roof vent + cracked window + constant low heat fixes 80% of condensation. The Karcher window vac and thermal covers fix another 10%. The last 10% is accepting that UK van life is damp in winter and staying on top of it.
