Which vapor barrier is recommended for this construction?

Hello,

we have renovated the roof structure in the old building and have now installed the insulation between the rafters. The rooms under the roof are a living room, a bathroom, and an office.

The following roof construction we have or plan:

· Clay tiles
· 80 mm insulation above the rafters (wood fiber boards Pavatex)
· 240 mm insulation between the rafters (wood fiber Pava-Flex)
· Dampfbremse
· Battens
· Drywall boards

Yesterday we visited the local building materials store regarding a Dampfbremse. They had two options to choose from:

1. A classic one with an sd value of 100 (this is "tight" and lets more or less "nothing" through)
2. A breathable one with an sd value of 2 (Delta Luxx from Doerken)

According to our carpenter, it does not matter which type we take. In other words, one that breathes on both sides like the Delta Luxx or one that is largely tight (with an sd value of 100).

We are now uncertain and wanted to ask for your opinion on which type of membrane you would recommend for this roof construction? Especially considering that one room will be a bathroom.

I would also be grateful if you could provide the exact designation of the vapor barrier (manufacturer and type) along with your recommendation. There are many different manufacturers such as isover, Würth, etc., etc.
So, which one is frequently used, enjoys a good reputation, and where is the price-performance ratio the best?

We would like to thank you in advance for any recommendation.

Best regards,
Markus

nobody an answer? :(

My knowledge is also that it does not matter. Whether that is really the case is another matter. A bathroom in a normal house is usually only temporarily exposed to higher humidity than other rooms through regular ventilation.

The best thing is probably to get advice from a professional.