I think I know the answer to this question. But I would liek to get some input.
Mow that hte weather has cooled off quite a bit and humidty levels are more moderate, I'm noticing that my indoor humidity levels upstairs have not changed much. My dewpoint mosture levels indoors are often higher than the outdoors. thsi was not hte case when it was hotter outside.
When I mved in, I had the underside of my roof deck spray foamed wiht 5-7" of open cell foam. I did not remove the existing cellulose at the time (I now realize I shold have removed ALL of it first). and as such they did the best job they could but I think it didn't get completely sealed at the rim joist where the hip roof meets the attic floor on the perimeter.
My theory is that all the loose fill cellulose insulation (That I probably need to remove form my attic) is absorbing moisture in the afternoon when reverse stack effect is most prevelent, then slowly releasing it in the evening.
I wonder is removing it would make a noticeable impact. I'm also concerned that the opposite will occur in winter. War moist air form inside hte house will exfiltrate out the same leaks and as those surfaces get cold, moisture will form.
Of course before I insualted the roof, the same issues would have been occuring.
If nothing else, the stuff is really nasty and would make doing any work much, much easier up there and would make it a more useable space for storage if desired.