In my 1950's house I have a 5'x5' square cinder block-walled, slab roofed abuttment that extends outside the foundation wall of my house behind a small door off the basement. It is entirely underground ~6" beneath a 5'x5' patch of ivy covered soil. The "room" houses my domestic water well head and pressure tank. The "room" does not have any form of intentional ventilation and the walls/ceiling are often damp. Exotic mold blooms have developed. I'm having the mold professionally removed, but I'm wondering what I can do to reduce the moisture in the room and reduce the potential for the mold to return. I suspect the outer walls of what we call "the goblin room" are not well waterproofed, but I'm loath to excavate. Someone suggested applying mineral wool to the inner wall might help as would putting a vent in the access door. I worry the former would just hide the problem and the latter might create a circulation path for mold spores into the main basement. Suggestions/opinions welcome.