Most attics are dry plywood is a smart vapor retarder with variable permeance.
Attic plywood wet.
The black attic mold shown here confirms that this attic had a serious venting and moisture problem including moisture from sources lower in the building.
Attic venting attic moisture and ice dams.
The attic vents provide a secondary method to help everything.
Attic insulation combination of fiberglass covered by cellulose.
It s not a vapor barrier.
Inner plywood of roof wet.
Some woods are much more resistant to rot and fungal attacks.
What to do about a wet attic.
In this photo of very dark mold in an attic in a wet attic mold which we found to be brown in the microscope looked black on the plywood.
Wanted to add more cellulose but installer said it would make wet roof worse.
The second variable is the species of wood used in the plywood.
Even if conditions are conducive to mold growth elevated moisture plywood made from a fungal resistant wood will resist mold growth for quite a while.
Wet sheathing was found in attic area due to lack of venting.
Not wet but some areas slightly damp.
Plywood is original 49 years old.
Quite often the roof flashing is defective and needs replacement.
Black mold in attics.
If the sheathing either boards plywood or composite board along the lower edge of the roof is soaked and you can see a corresponding accumulation of ice on top of the roof ice damming is occurring.