Is attic insulation without a vapor barrier okay?

Hi,

we have bought a 5-year-old KfW 55 house. The attic of the house is unoccupied, but it was insulated because of the gas heating installed there by the previous owner. The roof space is developed and inhabited. I have now noticed that the insulation of the roof in the attic does not have a proper vapor barrier. A foil was nailed over the insulation wool, but it is not sealed.

Can it stay like this?

Is it about an insulation between rafters?

How is the OG ceiling constructed? Has a vapor barrier perhaps already been installed there and the attic subsequently insulated by the owner, so that the hot water tank is not so cold? The heating system itself should actually not bring any moisture into the attic.

Is it about cavity insulation between rafters?

Yes, exactly. The insulation directly beneath the roof tiles

How is the upper floor ceiling constructed? Has a vapor barrier perhaps already been installed there and the attic later insulated as a DIY job,

The ceiling between the upper floor and the attic is also insulated and I (hope) that a vapor barrier is installed there as well.

Then I rather don't see a problem with that. Having a vapor barrier on top again would be nice, but it probably wouldn't be decisive.