I have a remote hunting cabin in a fairly dense wooded area in Wisconsin that I built 3 years ago with a yearly summer moisture problem.  The cabin is on a concrete slab (seems pretty dry after 3 years) and is stick built with sheetrock walls and ceiling.  Every summer the walls develop a significant mildew build-up that is pretty nasty.  The cabin seems quite damp throughout most of the summer (especially in the more humid months of July-Aug) despite leaving all the windows open for ventilation.  There is no electricity (propane, wood fireplace and intermittend generator use are my only energy sources) so a dehumidifier is not an option.  The cabin in not used at all in the summer months so I can’t just build a fire once a week or so to dry it out.  I assumed the problem was initially from moisture in the slab and that it would eventually resolve but it hasn’t improved at all with time.

Anyone have any ideas on how I could solve the problem.  I have considered a solar panel fan system to improve ventilation but am not sure if this will work as I already seem to get some cross ventilation from the open windows.  I may try to repaint the walls and ceiling with a mildew resistant paint but not sure if this will work.  Any other ideas.  Thanks alot.