Anyone else struggling with condensation in a small off-grid cabin over winter?

My little cabin is about 20m² with a single skin timber build, and every morning this time of year the windows are streaming and I'm getting damp patches near the roof junction. Running a small woodburner most evenings but clearly that's not solving it overnight.

Currently no mechanical ventilation at all — just a couple of trickle vents in the frames. I've been wondering whether a small 12V extractor fan on a humidity controller would help, powered off my Victron/Fogstar 200Ah LiFePO4 setup. Anyone actually done this and seen a measurable difference?

Also curious whether it's worth adding a vapour barrier retrospectively or whether that ship has sailed with an existing build. What insulation are others using in similar sized cabins — I went with 100mm Kingspan between the studs but I suspect the thermal bridging is doing me no favours.

@NicolaTaylor72 not my area exactly (I'm in a van rather than a cabin) but I deal with exactly the same condensation headaches in a much smaller space, so some of this might transfer across.

The single skin is your main culprit — there's nowhere for that moisture to go. In my van I noticed a massive improvement just from adding a small 12V fan to keep air circulating overnight, even without opening anything.

A few questions that might help diagnose it:

• Do you have any vapour barrier behind internal cladding?
• What's your ventilation situation — any trickle vents or roof vent?
• Is the woodburner vented externally or pulling room air?

The roof junction damp patches suggest cold bridging more than just humidity. Might be worth looking at where timber meets roofing material specifically.

Single skin is brutal for this — the wall surface temperature drops so far below dewpoint overnight that you're basically running a dehumidifier in reverse.

Few things that helped in my 18m² build:

• Vapour check on the warm side of any insulation you add, not just insulation alone
• Small 12v extract fan on a humidistat rather than running it constantly — pulls moist air before it settles
• Woodburner is great but cooking and breathing still pump out litres daily

The roof junction damp patches concern me more than the windows tbh — that sounds like cold bridging where the timber meets whatever your roof structure is. Worth investigating before it becomes a rot issue rather than just a condensation one.

I run a cheap SensorPush to log humidity trends overnight. Knowing when it peaks helped me time ventilation properly rather than guessing.

@NicolaTaylor72 single skin timber in a UK winter is basically just a very expensive outdoor shower — have you considered a vapour barrier on the warm side before you refit anything, because that roof junction will keep weeping until you do?

@NicolaTaylor72 had this exact problem in my garden office before I sorted the insulation. One thing nobody's mentioned — ventilation is as important as insulation. Counterintuitive but sealing everything up tight just traps moisture. A small trickle vent or even a basic humidity-controlled extractor fan made a massive difference for me.

Also worth getting a cheap hygrometer in there. Once you can actually see the RH% you'll know whether you're dealing with a ventilation problem or a thermal bridging problem — they need different fixes.

Damp patches at the roof junction specifically sounds like cold bridging at the wall plate to me. Bit of flexible foam tape along that junction before anything else might buy you some time while you plan a bigger fix.

@NicolaTaylor72 worth checking your woodburner has a dedicated air supply from outside if possible — burning wood consumes oxygen and draws in cold damp air through gaps elsewhere, which massively worsens the moisture cycle. Also, a small hygrometer is genuinely useful (cheap on eBay) so you can see exactly when humidity is climbing and ventilate briefly before it hits the walls rather than reacting after the fact. Even cracking a window for ten minutes in the morning when the stove's going can shift a surprising amount of moisture without losing much heat. @Rodney is right that insulation is the real fix long-term, but managing the moisture load itself is equally important — no amount of insulation helps much if you're generating condensation faster than it can escape.