Air in, air out
Over the years we have tackled the ventilation problem two ways.
First we added two of the ss Beckson vents on the cabin top, one over the head and the other over the aft cabin. We keep the hatches on their "vent" position most of the year, unless a major sideways rain is forecast. They work all the time, and required very little breeze to pull inside air out.
Next I added ventilation for all (!) of the closed off areas inside -- under all settees and other places with no vents. I also replaced all of the factory zip-open "doors" on all the inside lockers with exact replacements done with Phifertex (sp) inserts rather than the stock solid cloth centers.
For an Ericson with lots of teak doors, I would have installed teak louvers in all doors.
And speaking of Doors, our boat came with chrome hooks that hold all of them open a couple inches for ventilation I have some pix in my blog here titled ("Vent Method for Cabin Doors").
Lastly, we clean out all (!) of the "hidden" spaces once a year with bleach & soap & wet rags and wipe dry. Once you get ahead of the mold spores, it's pretty easy to keep them out. And lest you assume that this was always easy... our "fixer upper" boat was a veritable Mold Farm when we bought it in '94 -- looked gross and smelled gross.
Happy eradicating,
Loren
ps: I have heard examples of those solar fans for years on other boats, bad bearings crying for help. That was a reason we wanted only a "passive" vent.