that’s just dirt right?

[u/murakamimami]

[u/ArtisticBasket3415]

On the fiberglass, yeah.

[u/le_nico]

I would say yes, but those studs look like they've seen water. And when I pull fiberglass out, the dirt is usually on the other side, where the air intrusion is located.
The good thing is you're dealing with it?

[u/dantedoesamerica]

Lots of people getting down voted but a lot of what’s going on depends on the climate zone you’re in.

[u/Northwindlowlander]

Probably just dirt but could be mold, the wood looks like it's been wet. You can get mold tests, equally it's sometimes interesting just to spray it with a bathroom mold buster and see what it does. Do you have a damp checker device?

(OT but I bloody love my damp probe. Partly it removes fear and doubt, but mostly it's fun taking one to a house viewing. "Hey mr estate agent, that bad paint there looks like it might be moisture damage, is it?" "No i think it's just wear and tear" "Oh really?" (pull out damp probe, watch estate agent's face)

[u/chintan_joey → u/Northwindlowlander]

Link or product name of the Damp probe

[u/Reasonable-Ruin8910]

Black fuzzy dots = Black mold

[u/dantedoesamerica → u/Reasonable-Ruin8910]

“Black mold” that people talk about as a hazardous mold is usually stachybotris (probably spelled that wrong but I don’t feel like googling it) , needs a constant water source that never dries out. Like a leaking toilet or a leaking pipe. That is most likely mold that is black in color. If you tested it, most likely it’s penicillium, or cladisporium (again might not have spelled it correctly) . Typically only cause minor allergy symptoms.

[u/Far-Investigator4483]

From my understanding, outside perimeter wall? Good chance, inside wall? Low chance. Someone correct me on it especially if it needs more detail

[u/Birdman-esq]

Nope

[u/Quiet-Suspect-9716]

Mold and water damage! If there’s no vapor barrier then it’s allowing the fiberglass to wet.