Vapor tightness in inner vapor barrier with wood fiber insulation?

[JohanN03]

I'm putting up paper throughout my house from 1900. Cheap and easy, and it's been done before, so why change it? I'll use sawdust where I can, and in some outer walls, I'll use lin. I'm forced to change the panel in some places, and sawdust becomes impractical then.......

I've been thinking about doing that too. What kind of paper do you have? The house has sawdust insulation between planks, but I'm using wood fiberboards instead.

 

[KnockOnWood]

I have read, but can't remember where, that the internal vapor barrier should have at least 5 times higher vapor resistance in the internal "vapor barrier" than in the external wind protection.

And I have personally seen, in a new house that was not completely finished, how it had molded on the inside of the exterior gypsum. Inside the gypsum was cellulose fiber, but the inner panel was not completely finished, so it was possible to lift apart the insulation and inspect it.

 

[Rickard.]

At least 5 times denser in the wall and at least 10 times denser in the roof are guidelines, but this is solved by choosing a system from one manufacturer. One should not mix and match recklessly.

 

[JohanN03]

I have read, but can't remember where, that the internal vapor barrier should have at least 5 times higher vapor resistance in the internal "vapor barrier" as in the external wind protection.

And I have seen myself, in a new house that wasn't completely finished, how it had molded on the inside of the exterior plasterboard. Inside the plasterboard was cellulose fiber, but the inner panel wasn't completely finished, so it was possible to lift apart the insulation and inspect.

Mold only on the plasterboard or also on the insulation? Now, we don't know the circumstances, but it can still be interesting.

 

[JohanN03]

At least 5 times denser in the wall and at least 10 times denser in the ceiling are guidelines, but this is addressed by choosing a system from a manufacturer. You should not mix freely and take chances.

These are rules of thumb that I have also read about, but I don't know on what grounds they are recommended.

 

[witten]

Why complicate things with a diffusion-open interior?

 

[JohanN03]

Why complicate it with a diffusion-open interior?

Doesn't it result in greater moisture load in the rest of the house, especially at the junction between the extension and the older construction?

Edit: I should add that it involves an extension of about 25% of the original area and a small part renovation of an existing wall.

 

[Stefan1972]

I've been considering doing that too. What kind of papp do you have? The house has spån insulation between planks but I use träfiber in board form instead.

Regular grålumppapp......nailing horizontal paneling on all interior walls. Then it will be träfiber board. Just like it was before.

 

[JohanN03]

Common gray lump paper......nails horizontal paneling on all interior walls. Then it will be wood fiberboard. Just like it was before.

Now I'm curious. What kind of wood fiberboard is it?

 

[Stefan1972]

Now I'm curious. What is the fiberboard?

I haven't gotten that far yet, but it will probably be what's equivalent to tretex. There are similar boards available on the market.

 

[Daniel 109]

Doesn't it create a greater moisture load in the rest of the house and especially at the transition between the extension and the older construction?

Edit: I should add that it's an extension of about 25% of the original area and a small part renovation of the existing wall.

So little moisture gets through a vapor barrier that it doesn't affect the climate in the house.

 

[witten]

Doesn't it create a greater moisture load in the rest of the house and especially in the transition between the extension and the older construction?

No, how a wall is constructed does not affect the other walls in the house.

 

[useless]

Doesn't it create a greater moisture load in the rest of the house, especially in the transition between the extension and the older structure?

The vapor barrier is not meant to release excess moisture - that's what ventilation is for. Regardless of whether you have a vapor barrier or vapor retarder, it is never desirable to have moisture in the insulation. The difference is that with a vapor barrier, any moisture that gets in can still dry out, which can be useful, for example, during the renovation of an old house where it is difficult to install a comprehensive diffusion barrier without leakage at transitions between wall/ceiling, between floors, etc.

When building new and having the opportunity to install a comprehensive diffusion barrier, there is no major reason to use a vapor retarder instead.

 

[tompax]

Why?

Hunton Intello PlusApplications
Hunton Intello Plus is used as a vapor retarder, replacing the vapor barrier (plastic film) in all types of insulated and diffusion-open roof, floor, and wall constructions. The vapor retarder also ensures that building moisture can be directed inward in the building so that unwanted moisture dries faster. Particularly suitable for use in cabins and vacation homes that remain unheated for long periods.

https://hunton.se/wp-content/uploads/sites/17/2020/03/Nativo-träfiberisolering-Handbok-1219_SE_WEB.pdf

https://hunton.se/produkter/vagg/hunton-nativo-trafiberisolering-skivor/

 

[Daniel 109]

Construction moisture.....

Normally, there is a significantly greater moisture load from the inside than from the outside. In other words, this results in more humid insulation rather than drier.