How do I determine if the paper is diffusion-tight?

[andreasimolndal]

I am planning to add insulation to my house from the inside. The house is from 1956. The walls are built with several different layers with some type of wind barrier in between.

How can you determine if a wind barrier is vapor-proof or not? Is it possible to see this? Are there any tricks?

The walls are constructed as follows:
* surface layer
* tretex
* wood panel
* paper
* fiberglass insulation
* paper
* wood panel
* paper
* air gap
* brick

 

[Åsa Lund]

Not without taking down a piece of sample material.

I would just (without knowing exactly) assume that a paper from the 1950s has a wind-breaking function.

 

[andreasimolndal]

A piece of cardboard can probably be managed. How do I go about testing the steam resistance?

 

[larsbj]

The cardboard is 99.9% certainly not diffusion-tight. I have never seen diffusion-tight cardboard from that time, but upload a picture so it will be easier to determine what kind of cardboard it is.

 

[andreasimolndal]

Here are 2 pictures of the pappen:

 

[Pagno]

The paper can be convection-tight but not diffusion-tight. Why do you want a diffusion barrier? A convection-tight system is more than sufficient if there is adequate ventilation in the house/building. BUT it must be airtight!
The plastic can cause moisture to get trapped in the wall due to construction errors, creating unhealthy houses, mold in the air... Paper and flax-based insulation provide the best guarantees that there will be no damage in the walls and roof!

 

[andreasimolndal]

I do NOT want it to be tight because I am considering the following panels:
https://www.k-rauta.se/byggvaruhus/tilläggs-isolering-gips-40x600x2600

 

[Pagno]

Okay! Just check with the retailer to make sure it can be combined with the existing insulation, considering that you want prefabricated insulated walls with boards, there shouldn't be any issues, but you should never assume that warranties apply to all installations!
SPU AL has a system with foil on the inside and outside, seems to be a similar variant, good choice, saves a lot of money for the winter!
Good luck with the insulation!