Black frogs in the house and in the attic?

Hi everyone,

this is about a house that was built in 1995 and the previous owners rarely ventilated and more or less left the house to itself. This means it was not maintained, heated irregularly, and nothing has been renovated for 21 years.

Inside the house we saw black discolorations above the radiators and around picture frames. I think after 21 years that is normal as well.

However, when we were in the unused attic, we saw the black spots shown in the picture in the corner between the insulated floor slab and the uninsulated roof peak.
Is this just a concentration of the black "frogging" which can also be seen in the apartment, or was insulation done incorrectly here and is this mold or something similar?
The spots are almost in every intermediate area of the roof beams.
I would be grateful for your opinion.

Many thanks and best regards
Scharlie

I can only repeat the advice of and send an expert into the preferred house. That provides security. A forum cannot do this based on photos.

Frogging is green for me. Isn’t it called Fogging?

:-D yeah yeah... was probably still too early in the morning :-D