Waiving the vapor barrier in wood fiber insulation

Hi.

I took the construction example from the Steico manual. A vapor retarder is used on the inside there. See picture. The plan is to use a combination of above-rafter and between-rafter insulation with wood fiber.



Steico, for example, recommends the following vapor retarders



I am reluctant to stick a foil on the inside when using an ecological material like wood. We try to avoid plastics as much as possible.

Are there alternatives? I have read that when using OSB4 boards, a vapor retarder can be omitted. Steico also wrote in renovation reports that they only installed an airtight membrane between the above-rafter insulation and the between-rafter insulation.

Actually, I would like to have an OSB board under the rafter and then a drywall board. If you want to attach something to the roof slope, the screw would grip in the OSB board at the latest. Unlike foils, I do not think that an OSB board with tongue and groove can be laid completely airtight. What happens if I drill a screw through and later remove it again? Then there would be a filled "hole" in the OSB board.

Thanks. Best regards

OSB are also made with adhesive. So if you value healthy living construction, I would take a look at Baufritz. They invest huge sums in the research of modern bio-certified sustainable whatever building materials. If it could be done without brakes, they would do it ;)