ᐅ Roof Construction – Which Type of Vapor Retarder?

Hello,

we are planning to build a timber frame house with a vapor-open design. We have received an offer presenting different options for the roof construction, specifically regarding the type of vapor barrier. Could someone provide an assessment of the advantages and disadvantages?

-Roof tiles
-7cm (3 inches) battens / counter battens
-6cm (2.5 inches) wood fiber boards
-22cm (9 inches) rafters with wood fiber insulation
-Vapor barrier as a foil
-Battens / counter battens
-Gypsum board
-Wallpaper / plaster

This is the structure in the occupied attic. In the roof ridge space, OSB boards are used as the vapor barrier for vapor control, bracing, and cladding.

As an alternative for the occupied attic, I have been offered a vapor barrier foil made from thick paper/cardboard with mesh (manufacturer: Pro Clima) or OSB boards.

What are your thoughts on these options?

How is the attic space used? Is the ceiling of the top floor insulated?

The attic is traditionally used as storage space. The ceiling between floors is also insulated with wood fiber.

Pommes01 schrieb:
The attic is traditionally used for storage. The ceiling between floors is also insulated with wood fiber.

Instead of using foil, battens, and drywall panels, we simply screwed on OSB boards and glued the tongue and groove joints.
We might add diffusion tape over the seams.

It looks neat, requires less work, and reduces the overall build-up height.

And it is also better for summer heat.
I probably wouldn’t insulate the attic space.

I wouldn’t trust an OSB board as a vapor barrier inside living spaces. Besides, the surface would require a lot of work before you could put up wallpaper. I would also prefer a membrane over paper, since paper would likely be damaged even by a minor water leak, right?