Anyone else had condensation issues with their garden office in winter?

Dealt with this extensively last winter after converting a 4x3m timber cabin into a proper working space with a full Victron off-grid setup inside. The condensation was genuinely terrible — frost on the inside of the roof panels by January.

The root cause in my case was a combination of single-skin OSB walls with inadequate ventilation and the thermal mass of the battery bank actually contributing moisture as temperatures cycled overnight. Not something I'd anticipated.

What actually made a meaningful difference:

• Continuous background ventilation rather than just opening windows periodically — I fitted a small MVHR unit which transformed things
• PIR insulation boards on all internal walls, not just the floor and roof
• Vapour barrier installed correctly on the warm side of the insulation (so many guides get this backwards)
• Desiccant dehumidifier running on a timer overnight — the refrigerant types struggle below about 15°C so they're essentially useless in an unheated cabin in January

The battery bank itself (Fogstar Drift cells in a DIY 24V build) now lives in an insulated enclosure which also helped stabilise temperatures and reduced condensation around the terminals.

Still not perfect if there's a prolonged cold snap and I haven't been in for a few days. The space needs occupancy heat to really function properly.

Curious whether others have found structural solutions versus just running dehumidifiers constantly — feels like treating symptoms rather than the actual problem. What insulation approaches have people gone with on existing structures rather than new builds?

@PaulaFisher91 this resonates deeply — had identical grief with my shepherd's hut last January. The off-grid electrics actually made it worse initially; the inverter and battery bank were quietly adding humidity through thermal cycling.

What shifted things for me was a small Meaco dehumidifier running directly off the system during occupied hours, combined with vapour barrier stapled behind the tongue-and-groove cladding. Dramatic difference within a fortnight.

Worth checking your Victron MPPT and battery enclosure specifically — mine was acting like a cold bridge against the rear wall, pulling condensation exactly where you don't want moisture near terminals.

The hut is properly liveable now, but it genuinely took that whole miserable winter to understand what was actually happening with airflow and thermal mass in such a small timber structure.

Slapped a Victron SmartShunt in my motorhome years ago and still managed to grow enough mould to open a farmers' market — vapour barrier first, electrics second, lesson learned the expensive way.

@PaulaFisher91 what insulation spec did you go with on that cabin? Because in my experience the condensation is almost always a thermal bridging problem rather than a ventilation one — people slap PIR on the walls and forget the floor entirely, then wonder why they've got damp.

Got a static caravan that had similar grief until I sorted the underfloor situation. Made a bigger difference than anything else I tried.

Also — what's your heating setup? If you're running a small electric heater off your Victron system and not hitting a consistent temperature, you're basically creating a condensation machine every time it cycles off overnight. A decent thermostat controller makes a surprising difference to that.

What were your internal humidity readings during the worst of it? That'd help diagnose whether you've got a moisture ingress problem or purely a temperature differential one.

@PaulaFisher91 the frost on the inside is a classic sign your dew point is being hit on the inner face — means your insulation is either undersized or you've got a thermal bridge somewhere obvious like a floor joist or window frame.

Worth getting a cheap IR thermometer and mapping the cold spots properly rather than guessing.

On the electrical kit side — Victron gear generates a surprising amount of heat which actually helps, but it also means any cold shutdown can create localised condensation on the components themselves when temps swing. I run a small Victron cerbo in my static and had moisture ingress on connectors until I stuck a desiccant pack in the enclosure.

Vapour barrier placement matters enormously. Warm side of insulation, not cold. Most timber cabin manufacturers bodge this completely.