Anyone else finding condensation a nightmare in their cabin this winter?

Not a cabin as such, but dealing with the exact same battle on my narrowboat — so I imagine the problems are pretty much identical.

The single biggest change I made this year was fitting a Webasto diesel heater and running it on a timer to keep temps from dropping overnight. Before that I was waking up to rivers of condensation on every single window and the walls were starting to look worrying around the corners.

A few things that seem to actually help:

• Vapour barrier behind the lining panels — wish I'd done this during the original fit-out rather than retrofitting it bit by bit
• Running a small dehumidifier overnight (pulling about 40W, so manageable on my Victron/Fogstar setup)
• Keeping the wood stove going longer into the evening rather than letting the boat cool rapidly

What I still haven't cracked is the condensation forming inside the roof panels where I can't easily get to. Moisture finds its way in during fitting no matter how careful you are.

Curious whether cabin folk are dealing with the same internal cold bridge issues? I'd imagine timber framing creates slightly different problems to steel — or does it end up being just as bad in practice?

Also wondering whether anyone's tried those silica gel tub things as a supplementary measure or if they're basically pointless at scale?

@MultiPlus_Queen interesting point about the Webasto — forced-air diesel heaters do a decent job of keeping RH down because they're pulling combustion air from outside rather than consuming indoor air and dumping water vapour into the space like an unflued propane burner does.

On my setup I've found vapour barrier continuity is the real battleground. Condensation isn't just a heating problem — it's where warm moist air finds a cold surface. Even a small gap in your insulation layer creates a cold bridge and you'll get localised dripping regardless of how hard your heater works.

Worth investing in a decent hygrometer (I use a calibrated SensorPush) and logging overnight RH. If you're consistently above 70% even with heating running, you've got an air infiltration issue rather than a heating deficiency.

Both worlds here — narrowboat and static caravan — so condensation has been my nemesis for years.

The thing nobody mentions alongside any forced-air heater is thermal bridging at your windows. I spent a winter puzzling over why my RH stayed reasonable but I still had rivers running down the glass every morning. Turned out my aluminium-framed windows were acting like giant cold fingers poking into the warm interior.

Fitted secondary glazing on the static (cheap Perspex DIY job, not pretty) and the difference was genuinely embarrassing — should've done it years ago.

On the boat I use a small Govee humidity sensor linked to my phone. Once you can actually see the RH climbing in real time, you understand exactly which activities — cooking, drying clothes, even breathing in a small space — are the real culprits.

Slightly off-topic as mine's a van rather than a cabin, but the condensation battle is identical so hoping this is useful —

Has anyone looked at vapour barriers on the walls before insulating? I made the mistake of just slapping 25mm Celotex straight onto my van's metal skin and the cold bridging was horrendous. Redid it properly with a layer of foil-faced foam and the difference was noticeable immediately.

Also curious what people are using to monitor RH — I picked up a cheap SensorPush and it's been eye-opening. Some mornings I'm hitting 80%+ before I even boil a kettle.

@DerekDixon you mentioned something nobody talks about — genuinely curious what that is, your post seems to have got cut off?

Spent three winters on the narrowboat convincing myself the damp was "character" before admitting I'd basically been living inside a cloud — thermal mass in a steel hull is genuinely cursed.

One thing nobody's flagged yet: vapour barriers on the cold side are a trap — you just move the condensation point somewhere you can't see it and discover it six months later when your insulation looks like a wet sponge.

Also worth noting that a cheap hygrometer (few quid on Amazon) will tell you more about what's actually happening than any amount of poking walls — I run mine alongside the Victron kit and the correlation between solar charging cycles dying off in winter and RH spiking is deeply depressing data to own.

Three winters on the motorhome taught me that condensation is basically your breath coming back to haunt you. The single revelation that changed everything for me was understanding the dew point — your walls don't care how warm the air feels, they only care what temperature they are.

On the narrowboat I now run a Victron SmartShunt monitoring exactly how much power my ventilation is pulling overnight. Sounds nerdy, but it told me I was running the fan too hard and actually increasing moisture ingress through a poorly sealed vent.

Two practical fixes that cost almost nothing:

• Moisture-absorbing panels behind cushions where cold steel lurks
• A cheap hygrometer — keep relative humidity below 60% and you've essentially won the battle

@OffGridGeek — "character" is just what we call mould when we're in denial. Been there, mate.

Relate to this hard — static caravan winters are brutal for condensation. The walls are essentially cold metal sandwiches.

Two things that genuinely shifted things for me beyond the usual advice:

1. Vapour barrier on interior walls where I'd ripped back the original lining — made a noticeable difference to cold bridging
2. A small Mitsubishi wall-split running in dry mode overnight rather than full heat — barely touches the battery bank and pulls surprising amounts of moisture out

Also worth checking your skirting situation if you've got a static. Ground moisture wicking up underneath is often contributing to overall humidity levels more than people realise — I sealed mine with rockwool and a breathable membrane and it helped considerably.

@OffGridGeek that "character" phase is real — I told myself the same thing for about a year before the window frames started going mouldy.

Good thread this. One thing I'd add that nobody's mentioned yet — thermal bridging is often the silent culprit that defeats everything else you try. You can insulate brilliantly but if you've got metal fixings, roof rails, or structural frames conducting cold straight through to your interior surface, you'll get persistent cold spots that attract moisture no matter what. Worth getting a cheap thermal imaging camera (or hiring one for a day) to find your actual problem areas before throwing money at ventilation or heating. Sorted two stubborn damp patches on my shepherd's hut that way. Saved me a fortune in trial and error.

@MultiPlus_Queen knows what's what — narrowboats and van conversions are basically identical battles, just one floats.

My van conversion nearly defeated me third winter in. Found moisture pooling inside my Fogstar lithium battery box one morning, which was a genuinely alarming Tuesday. Turned out I'd created a perfect cold pocket behind the wheel arch by insulating around rather than over it.

@Bazza49 is dead right on thermal bridging — that wheel arch was basically a radiator running in reverse.

The fix that actually worked: a small Govee hygrometer in every distinct zone. Cheap as chips, logs overnight data, shows you exactly where the problem's hiding before it finds your electrics first.