Insulation of the top floor ceiling?

Hello,

we bought an older house last year. One part of the house had already been completely renovated 10 years ago. The rest of the house still needs to be renovated. Initially, we renovated the area that had already been renovated.

Now we face the mammoth task of renovating the rest of the building. At the moment, this part is still completely separated from the area where we currently live. It will be joined together through a breakthrough. I hope that was understandable so far.

I now wanted to start with the attic. The attic is accessible but cannot be made into living space. The boards on the attic floor are brittle and should now be replaced with 22mm OSB boards.

I have now started removing the boards. Underneath there was a layer of glass wool. However, there is no vapor barrier installed under the glass wool. Under the glass wool, between the wooden beams, is a layer of small boards and below are wood-cement-fiberboards installed.

In the part of the building that still needs to be renovated, I will be renewing the ceilings anyway and installing new insulation wool with a vapor barrier.

But what do I do now in the area that is already inhabited? Affected by this are a children's room, a laundry room, and part of the hallway.

To do it properly, I would basically have to completely redo all ceilings. Are there any other options?

Are you worried now because of the missing vapor barrier? What is your goal anyway? To redo the insulation because the old one is not good? Is there cold air coming down from the ceiling or what is the specific problem?

If it is only about the flooring in the cold roof, the easiest solution would be to lay tongue and groove boards instead of OSB. They are permeable to diffusion unlike OSB and you can initially leave the insulation as it is.

But if you want to redo everything anyway and insulate to a 'modern' level, you would have to redo all the ceilings, yes.