On Friday, February 8, 2019 at 8:35:59 AM UTC-5, wrote:
7:40 wrote:

"I think the crux of the issue is not really insulation - but rather
ventilation ... is your "storage " area going to be well
ventilated to the great outdoors - or sealed off from outside
temperatures ?
John T. "

In a traditional unoccupied attic, the only thing the roof keeps
out is the beating sun in summer, and precipitation and strong
winds year round. Other than that, it is ventilated, around the
edges where the eaves meet the attic deck, and optionally,
via a ridge vent along the peak. That is why we insulate the
attic deck(the ceilings of the highest rooms in the house).

This should be common knowledge John.

Agree. The OP doesn't say how the attic is ventilated. Without adequate
ventilation, air won't move to equalize humidity levels between inside
and out. Also, is there a vapor barrier on the insulation in the attic,
facing the living space? Is he sure that all bath vents, dryer vents,
etc are properly run outside and not into the attic? And regardless of all
of the above, I would think there would be periods where the humidity level
inside the attic will be much higher than outside. If it was humid outside
at 65F and then at night the temp quickly drops to 35F, the humidity will
go up until enough air moves to equalize it again.