Revisions log for Answer #844

Start by buying a weather station with a remote sensor. Place the sensor in the basement, in the dampest place. Start observing.

Try to change the position of the fans in the vents, the heat fan inside the basement, by lifting the pipes through the corner of the vents along the wall on one side. On the basis of the indicators you will be able to draw conclusions

There may be differences in winter and summer. The humidity of the basement is a purely individual value and many components can affect it.