ᐅ Attic Insulation Using Wood Fiber Insulation

Hello fellow builders,

Our shell construction is complete, and soon we need to focus on the roof insulation.

Current situation: Roof tiles will be installed this week.

Roof battens
Counter battens
50 mm (2 inches) wood fiber boards

Now, what about the interior?

Our energy certificate specifies the following roof structure:

50 mm (2 inches) wood fiber insulation WF DIN EN 13171
200 mm (8 inches) mineral wool MW DIN EN 13162 035
PP foil ≥ 0.05 mm (0.002 inches)
30 mm (1 inch) *static air layer, heat flow upwards
15 mm (0.6 inches) gypsum plasterboard DIN 18180

From what I have read, the wood fiber boards are vapor permeable. So, it should be possible to install insulation between the rafters.

But which type of foil (vapor retarder/ vapor barrier/climate membrane) should be used?

View between the rafters

We also need advice regarding the attic. What is the current best practice here? If the roof slopes are fully insulated up to the ridge, should the attic space itself be additionally insulated with mineral wool or similar, including the appropriate membrane?

Thanks for your help and suggestions.

Best regards