[Anahki]

The biggest problem with the mold growing in such locations is that they are a kind of "perfect storm": humid weather, countryside location and organic materials (wood) to construct the buildings... They will never get a permanent solution save for the most expensive ones (rebuild with brick/concrete, double window and proper wall isolation). Anyway, it could help if they keep a proper ventilation routines on the affected rooms, avoid leaving clothes inside to dry (some people don't have drying function in the washing machines) and using painting and varnishes to protect the wooden surfaces, and washing/cleaning the rooms at the very first sign of mold. But as I said, the solution is complicated.