moulded very badly the first winter I had it. It was buttoned up fairly tight with only minimal ventilation. After a long job of cleaning up all the black stuff I went with a small fan, a 100W open light
bulb, and most of the jalousie windows
open a touch. No more mould, and we get very damp, cool winters here. (the rest of the seasons too, but hey, we got TREES!)
The little fan has been running night and day, all year long for over three years now. What a fine little device.
100W bulbs are getting hard to find, but I did get a lot of them a while back when the local Home Depot was blowing them out.
Simple solution to a problem that was a real bear to clean up from.