Mysterious musty odor permeating house
This is such a strange situation...really hope someone has some insight. Is there such a thing as a fungus that only stinks in the AM? For the past month or so there has been a musty odor permeating the house, strongest on the 2nd floor (sometimes stronger in one room; strongest in 2 out of 3 upstairs rooms), less pungent on the 1st floor, barely noticeable in the basement. The noisome assault begins sometime after sunrise (it usually gets potent enough to wake me around 9:00 AM) and gradually diminishes until early afternoon. Then it disappears (the master bedroom stinks the longest) and we get a reprieve until the following morning.
I thought maybe it was a plumbing issue, but the odor seems to be strongest in the master bedroom. I'm wondering if it could be water damage in the attic or moisture seeping into the ductwork near the bedroom. Do either of these theories sound like possibilities? Anyone have a different theory?
Thanks in advance for any help in cracking the case of the Malevolent Morning Mustiness.