The previous owner tampered with the insulation. Do I need to do something?

Hello,

first of all, I am an absolute layman and have little knowledge of handyman topics. It’s about a low-energy house built in 2012. The attic is insulated with mineral wool and a vapor barrier (or vapor retarder?).

Recently, the previous owner told me that birds once nested in the gable. On this long beam where the roof slopes rest. He had to insulate and close everything from the inside at one point (he is not a handyman himself...).

When I wanted to check directly at home, I found this upstairs (see photo).

The previous owner says he put new foil on, glued it back to the wall with the appropriate adhesive, and additionally sealed it with tape. Reinserted the insulation behind it. Does that look okay or should I have a professional check everything?
By the way, I feel a very slight draft upstairs. The lighter test was normal, however. A hanging hair on the ceiling moved slightly. Shouldn’t it be completely airtight? So that you don’t feel anything? I crawled around everywhere but couldn’t find any damage to the foil....

Maybe someone has advice. Best regards

A hanging hair on the ceiling was, however, slightly moving.

Oh dear, of course the concern is justified ;)
Did you breathe? Did you move? ;)
No, seriously:

Shouldn't it be completely airtight?

That's the cold roof! And without plaster, nothing is airtight.

Oh dear, of course the concern is justified ;) Did you breathe? Move? ;) No, seriously: That’s the cold roof! And without plaster, nothing is airtight.

Ah ok. I thought if the foil is completely under the roof, it has to be 100% airtight. Thanks for your contribution

Indeed, the question here is why there is still a foil installed on top. For a construction year of 2012, the seller should still have all the documents. In this respect, I would check what should be behind the foil and whether it is relevant for thermal insulation. Also check the ventilation of the attic. A cold roof should be ventilated, then the insulation of the roof slopes and the vapor barrier can actually be omitted.

Well, isn't that a ventilation duct (flat channel)? It has to be within the thermal envelope, maybe that's why the roof was insulated afterwards. No idea if the ceiling insulation actually had to be removed then...