Preventing damp/mould over winter

[Condi]

The caravan is getting damp over winter, and mouldy in places. I have usually had the roof vent open, trying to keep air moving and to keep temperatures inside and outside roughly equal to prevent damp, however this is clearly not working.

Next plan is to put a header and/or dehumidifier in once I get some electric to it.

Can anyone suggest what temperatures and humidity levels are likely to be acceptable to prevent mould? I have got a thermostat and humidity switch, so can set them to come on at given levels, but I was thinking maybe 8 degrees and 60/70% humidity? Or is there a better way to do it?

[donaircooleone]

Has it got any water ingress ongoing or new?

All vents and high/low level drops clear? We are seeing a fair number of 'vans where customers think blocking these are a good thing (it is not).

They don't generally get damp / mould build up when laid up appropriately.

[Condi]

I think its just moisture in the air coming in via the open top vents, and then condensing. Maybe when it rains there is some which splashes in via the vents, or blows in. Am pretty sure its fundamentally dry.

Sounds as if the obvious thing is just to close the vents, but then there wont be any air in it at all.

[DirtyHands]

Airflow is key. Make sure all high level and floor level vents are unobstructed. I also recommend having a window or two left on the vent latch. Winter covers normally make problems worse as the restrict the free flow of air.

[missing the VR6]

We have a couple of those £1 moisture collector things from Poundland or wherever, seem to be doing a good job so far in our nearly 5 year old motorhome.