Vapor tightness in inner vapor barrier with wood fiber insulation?

[KnockOnWood]

The vapor brake also ensures that construction moisture can be directed inward in the building... Particularly suitable for use in cabins and vacation homes that remain unheated for long periods.

In unheated buildings, it's not common to install either a vapor brake or barrier, right?

 

[JohanN03]

I still can't figure this out.

If I add an extension, I increase the total volume of the house. If the extension is built completely vapor-tight but the existing house basically has straight pipes through the wall, then the extra air volume in the house that holds the moisture should increase the moisture load on the diffusion-open structure of the old building. Having proper ventilation doesn't prevent vapor transport through the wall.

Help me think this through

 

[useless]

If you have straight pipes through the wall, that's where you should prioritize the work.
If those living in the house produce as much moisture as before the extension, the moisture load decreases with the increased house volume.

 

[ArneTW]

Whether it's right or not, I will probably never build or renovate anything "tight."

Asfaboard and vapor barrier for the win.

/ATW

 

[witten]

There is usually not much more moisture in the air indoors than outdoors, so the air volume doesn't matter.

 

[witten]

Regardless of whether it's right or not, I will probably never build or renovate to something "airtight."

Asfaboard and vapor brake for the win.

/ATW

An emotional argument that might be okay to have personally but not to impose on others. We don't have a problem with moisture damage due to vapor barriers in this country; on the contrary, we started using them to avoid moisture problems.

 

[ArneTW]

An emotional argument that may be okay to have personally but not to impose on others. We don't have a problem with moisture damage due to vapor barriers in this country; on the contrary, we started building with them to avoid moisture problems.

Impose...

I don't agree that a wall with a vapor brake on the inside, wood fiber insulation, and asphalt board on the outside would somehow be worse for the wall's health... I don't understand those of you who praise plastic in the wall, claiming it would be healthy and without problems, I don't agree...

What does the curve for tighter houses plotted against allergy/asthma look like?

/ATW

 

[JohanN03]

If you have straight pipes through the wall, that's where you should prioritize the work. If the residents of the house produce as much moisture as before the extension, the moisture load decreases with increased house volume.

The original construction should not be touched. It has worked well for a hundred years.

I think that indoor moisture is more influenced by the properties of the outdoor air via the supply air, which varies greatly over the year than by the residents.

The volume in the building increases with the extension, which provides greater available moisture content in the air, but the total diffusion-open area remains constant.

If the new part is built with diffusion-open properties, the total wall area increases and the insulation in the old part is less burdened. Still a wrong idea?

 

[useless]

The misconception is still that there should be some form of moisture migration from the indoor air into the insulation.
The vapor barrier has the opposite function - That moisture in the insulation should be able to dry out.

 

[JohanN03]

The misconception is still that there should be some form of moisture migration from the indoor air into the insulation. The vapor retarder has the opposite function - That moisture in the insulation should be able to dry out

But it must be a scenario that occurs only with negative pressure in the building. Otherwise, we always have moisture migration towards the outer part of the wall. Creating constant negative pressure in an old house is not possible.

Then I can imagine (rather guess here) that moisture migration occurs differently over the height of the wall and in the ceiling?

 

[witten]

Press...

That a wall with a vapor barrier on the inside, wood fiber insulation, and asphaboard on the outside would somehow be worse for the wall's health I disagree with... I don't understand those of you who praise plastic in the wall as being healthy and having no problems; I disagree...

What does the curve for more airtight houses plotted against allergies/asthma look like?

/ATW

You might have been unfairly accused, but it was someone who wrote that it MUST be a vapor barrier. There are a few cases where it must be, but those are not the ones we are talking about here. Plastic healthy? Do you mean that it is unhealthy? By the way, a vapor barrier is also made of plastic.

I don't get the last line? Are you insinuating that allergies increase if you have a plastic film in the wall with extremely high vapor resistance (vapor barrier) but not if you have a plastic film with only high vapor resistance (vapor barrier)? Allergies are believed to be due to reduced exposure to dirt and bacteria.

 

[ArneTW]

I might be wrong about what ångbroms is... I was thinking of something like wind barrier...

But then we'll skip ångbroms entirely.

Yes, I do actually claim that today's airtight/well-insulated houses contribute to allergies and asthma.

/ATW

 

[Daniel 109]

It was built with some unsuitable techniques during the same period when plastic became standard. But I haven't heard of any connection between building plastic and allergies. Do you have any kind of evidence for that opinion?

 

[tompax]

In unheated buildings, you typically don't install a vapor barrier or retarder.

Maybe they mean buildings that are periodically heated?
It says: "Particularly suitable for use in cabins and holiday homes that remain unheated for long periods."

 

[useless]

I might be wrong about what a steam brake is... I pictured something like windproof paper...

From an allergy standpoint, it's not good to have asphalt-impregnated paper on the inside of the wall.