Just would like to add that a solution I've been thinking about is bag
sealing the things that may have to go in the basement. The bag itself
is 100% moisture proof and whatever small wear holes there are or
the tie around the bag opening would admit some air and therefore
humidity, but it would cut the air exposure rates down by a factor of
1000's to 1, I would think. May have to back it up with Dessicant in
the bag too.
Uline.com, for one, can sell that in bulk for this purpose.
Seal the bag in the climate controlled area first and then put that in the
basement to start off well.
John A.