What is being worked with, at the moment, is a sealed room inside the home that has no ducts into it (yet) and an electric de-humidifier dedicated to that room alone. There is another de-humidifier elsewhere in the basement. With all the concrete involved (including the floor) it just seems that over time after everything's been closed/locked up for a while that it's "stale" or whatnot in there. Not quite wanting to say 'musty' as that implies to me 'moisture' and the de-humidifier is taking care of that.
But after leaving the door open for a while, and the fan on (oscillating fan) thing seem to normalize. Maybe one should just leave some Hoppe's 9 out in a pan or something, but for a person like me to actually notice it upon walking in there, it's something to be concerned with. Otherwise I myself wouldn't bother.
I was thinking about building a heat-exchanger and/or ducting in some HVAC as well as return vents. Just don't want to create vulnerable points.
The Blessings of having this situation to begin with, is a huge deal in its own. This 'problem' (if one could call it that) is of a minor issue and one of just 'tweaking the last few details' but we all just want to ensure that no further problems are going to come up. Rust is obviously a concern, always. Temperature differential being the first thing to avoid. But being the first to admit that I don't know everything yet (gimme another week

) I just want to head things off at the pass before finding out after that "something huge" could have been prevented by "something minor" in comparison.
Thing is, there really isn't much of a venue, anywhere that I know of, for researching/discussing "problems" such as these. Woe is us with our First World luxuries, eh? Oh, the dilemma....