What is the sd value for the vapor barrier?

Hello everyone,

I have already tried searching, but haven't found anything 100% suitable.

I am wondering which vapor barrier I should take.
So far, I have two offers. A Topfol with sd>100 and the Siga Majpell with sd>5.
I myself was thinking of one with a variable sd-value.
However, the plasterer has expressed concerns, saying that these would open up in the cold season and the moisture could cause problems then.
I have the following construction:
Delta Maxx Plus
200mm WLG 035 fleece insulation
Vapor barrier with questionable sd-value
40mm counter-batten WLG 035

Siga offers the Majpell once with an sd-value of 5 and once with 25.
What should one take now, or what should I make this dependent on?

Regards

Don't understand the structure. Vapor barrier or vapor retarder? For a vapor retarder, I would take one with sd 2-3, maybe a Proclima DB.

I myself thought of one with a variable sd-value.

Why? What advantages do you expect from it? There is no critical construction that would allow condensation or accumulation in the insulation.

The further outwards in the insulation layer the foil is located, the more permeable it should be. With insulation under the rafters, never a vapor barrier (sd >1000m). Everything else depends on the ventilation situation of the roof, existing insulation above the rafters, the sd-value of the insulation between the rafters, and the sd-value of the underlay membrane.

I wouldn't know why you would need more than 5m of sd-value. Everything beyond that has at most 0.5m and is ventilated.