Insulating wooden beams of the attic ceiling

Hello, I don't know what to do. I have now read many pages about vapor barriers, yes or no. We were advised to lay styrofoam boards on the existing floorboards and OSB boards on top of that.. the floor should remain walkable. I am attaching several pictures for better explanation. We have a wooden beam ceiling.. in between are sauerkraut boards and partially rubble on top... Now the questions.. Should we remove all the wooden floorboards and lay insulation between the beams? Or just put styrofoam boards on the floorboards and OSB on top? Do we need a vapor barrier here? If yes, does it have to go on the "sauerkraut boards" and then insulation on top? I have no idea what is best here, help!

if you wanted to insulate between the beams, you would definitely need a vapor barrier underneath (barrier vs. retarder vs. climate membrane, all different). Otherwise, the moisture from the person in the room below would cause your insulation to mold. This vapor barrier must be sealed almost 100% airtight up to the four walls. Pay attention to the attic hatch. That could be difficult because you would have to tear down your entire existing ceiling in the rooms below for that.

Alternatively, I could imagine that you could lay a foil on the floorboards or below on the beam layer, insulate it with polystyrene panels, and then lay OSB on top again, but I can't say whether that makes professional sense.

It could also help to get a subjective opinion from the building materials dealer. They probably want to sell their products, but you can definitely get valid alternatives with prices.

Hello Matafox, I am facing a similar question. Have you made a decision? What exactly are the "Sauerkrautplatten" for you? Heraclitus? Regards

Hello, so I’m joining in here. In spring 2018 we are facing the same problem and don’t know yet exactly how to handle it. We also have the sauerkraut boards, I think Heraklith boards.

Regards

Please describe the entire setup and exactly what is done and to what extent.

So, I'll describe our setup:

16 cm wooden beams
Heraklith boards
Plaster

We removed the boards on the wooden beams. Between the wooden beams there was partly slag, which we also removed. In some places there was no insulation at all. Unfortunately, it is not possible for us to remove the Heraklith boards because the rooms below are in use.

Our current plan is:

- 160 mm insulation between the beams
- OSB boards screwed onto the beams
- to even out, we will probably need a dry fill because the top of the wooden beams has height differences of about 7 cm
- OSB boards laid floating on the fill
- vinyl or parquet flooring

Now the question is how we handle the vapor barrier / retarder? And whether it makes sense to use tongue and groove boards instead of OSB boards. The price is about the same.