Took down fiberboard after recommendation here. Now what?

[MathiasS]

The black is a vapor barrier that you must put back in place, I believe the original name was alkydpapp or something like that and it is not a vapor barrier like plastic but a combination of wind protection and diffusion-retardant paper, so you need to put up a new one to protect the outer walls

I had that throughout the house (the walls had kutterspån). I think it had zero moisture-blocking function given how it was installed, etc., but I have replaced it with age-resistant plastic in conjunction with additional insulation both inside and outside.