Simon Waddell wrote:
I live in central Europe - where the weather is neither too hot nor too
cold.

Seems to me that in the not too distant past many people fitted little solar
powered extractor fans to their trailers to improve ventilation. Looking
round our club trailer park the other day I noted that only one out of 25
trailers was so equipped.

What are the pros and cons of fitting such fans and is there a trend not to
fit them?

If the source of the moisture were from inside the trailer then one of
these vent fans used for drying would make more sense to me. As it is
I believe all they can do is draw outside air, at whatever humidity it
may be, into the trailer. Now if the vent fan is only turned on when
the outside air is relatively dry then perhaps there is some logic for
trying to dry the inside of the trailer. But this scheme is hopeless
when the outside air remains wet for days (weeks?) on end, IMHO.

The route I have chosen is to seal the trailer up as tightly as
possible and install a small dehumidifier inside the trailer. I then
do whatever it takes to get power to the trailer to run the
dehumidifier. The extracted water is drained through a small screened
hole in the bottom of the trailer. It all stays bone dry inside even
during the wet season where it can rain continuously for days or weeks.
The dehumidifier cycles itself on and off as necessary via its
built-in humidistat.

Regards,

-Doug