I have a cabin in Northern Wisconsin that is 2 years old (concrete slab, standard stud walls with drywall).  The cabin is in a fairly dense woods and is in the shade most of time.  Every summer I get mold forming on the walls and ceilings to the point where I have to clean them with bleach (a real pain).  I don’t have a vapor barrier under the slab but there doesn’t seem to be moisture coming up from the slab since I can tape down some poly on the floor and it remains dry throughout the year.  The cabin is unoccupied throughout the summer months (quite humid summers here) but up till now I have kept the windows open for ventilation.

Here is my question.  Someone suggested to me that the solution would be to simply seal it up throughout the summer months (keep the windows and doors sealed shut) to prevent condensation between the cooler walls and the warmer, humid air that blows in during the day.  I am on the verge of spending a fair amount of money on a better ventilation system (I don’t have electricity here though and it will require some type of a wind driven system).  Is there enough logic in this simple solution that I should try this for a year and see if it works.  It does seem to make some sense to me but I would appreciate any thoughts from some builders.