Vapor tightness in inner vapor barrier with wood fiber insulation?

[tompax]

Do you have any more information supporting that the houses would become worse just by being wrapped in plastic? In most cases, the plastic is installed in connection with renovation, additional insulation, changed usage, and a change of heat source. Then blame the plastic when something goes wrong...

Exactly what goes wrong with wrapping, I guess, varies from case to case, depending on the original construction, the location of the house, the indoor climate, and other factors like the insulation material used, etc. But we've heard and read a lot about houses that have deteriorated after changing the original conditions during renovations. Then exactly what is behind it, plastic or something else, varies.

But my point was that over 100-year-old wooden houses built with natural materials like pure wood that can buffer moisture, etc., are still standing today and are usually healthy.

 

[tompax]

Because they have thin insulation in them, the wall is warmer all the way through.

There is a large temperature difference across the wall. Wood can handle a lot of moisture before it becomes so damp that mold thrives. Fireplaces draw out a lot of air, creating negative pressure in the house and ventilating out the moisture. It’s not because they lack a moisture barrier.

But you mean that newly built houses with cellulose insulation and no plastic, only a vapor barrier and asfaboard as wind protection, that these houses would be a risky construction and mold as well, because of the thick insulation compared to old wooden houses that have no insulation at all?

 

[Daniel 109]

As long as the vapor barrier is sufficiently tight, it will work. What I mean is that there are no advantages to a vapor barrier compared to a moisture barrier. Rather the opposite. But it will also work with a vapor barrier if it is sensibly dimensioned.

 

[tompax]

What I mean is that there are no advantages to a vapor brake compared to a vapor barrier. Rather the opposite.

Ok, I'm not disagreeing. But why should it be vapor brake instead of vapor barrier according to cellulose insulation manufacturers?

I have personally built according to that method and it was supposed to be a vapor brake according to the manufacturer, nothing else. It was also ok to use a vapor brake from another brand, as long as it matched the manufacturer's own specifications.

 

[guggen]

There are many misunderstandings when it comes to brake vs barrier, etc. The first is that in most cases, both are quite tight and none are completely tight, so it's always about a scale of tightness. The second important point is regarding old houses where an exterior air gap is typically lacking. No problems as long as no one idiotically paints the house with modern dense junk paint. But having a brake in this case means avoiding having a completely tight wall, which is disastrous. The taboo against plastic/barrier in old houses often concerns the combination of plastic on the inside and plastic (paint) on the outside.

 

[KnockOnWood]

Mold only on the drywall or also insulation? Now we don't know the conditions but it can be interesting anyway.

It was easiest to see on the light drywall paper.
Whether there was mold inside the cellulose as well and if it was replaced I don't know.
But it's likely that the mold also grew in the outermost layer of the insulation.

 

[Stefan1972]

Then you can't compare different houses and constructions either. Even if one has done it in a certain way, it doesn't mean it can be made a norm. All houses become almost individual unless everyone builds exactly the same. How air travels in a house can only be determined through careful studies over a long period, and that is not currently being done. Nowadays, construction is done in an accepted way. That way, you don't have to think about anything. You more or less skip the moisture migration in the wall and ventilate it away instead.

If you want to disregard the plastic, you can of course do so, but then it's more that you take the consequences yourself, and you should then know what you are doing and choose materials accordingly. You can't ignore plastic just because they didn't have any 100 years ago..........

 

[useless]

Another misconception is that all houses were better in the past. Sure, those that have stood for 100 years probably have some qualities, but that doesn't mean that all houses from the past were much better and free from problems with moisture and rot.

https://byggnadsvard.se/inte-battre-forr-kort-livslangd-pa-husen/

 

[guggen]

Another misconception is that all houses were better in the past. Sure, those that have stood for 100 years probably have some qualities, but that doesn't mean all houses from the past were much better and free from problems with moisture and rot.

[link]

Compared to the 70s and 80s, most houses were probably better in the past, but anything not maintained will eventually go to ruin. However, today we undeniably have good building standards, and today's houses will likely stand for a hundred years with reasonable maintenance.

 

[Daniel 109]

Then you cannot compare different houses and constructions either. Even if someone has done it in one way, that doesn’t mean it can become a norm. All houses become almost individual unless everyone builds exactly the same. How the air moves in a house can only be found out through careful studies over a long period, and that is currently not being done. Nowadays, houses are built in an established way. Then you don’t need to worry about anything. You more or less skip moisture movement in walls and ventilate it away instead. If you want to skip the plastic, you can, of course, do that, but then it’s more about dealing with the consequences yourself, and you should know what you’re doing and choose materials accordingly. You can't just skip plastic because they didn’t have any 100 years ago..........

Here, I do not agree with you. You can absolutely compare different houses. It's also not some kind of magic with how moisture in buildings behaves. It can be predicted relatively well.

 

[tompax]

Then you can't compare different houses and constructions either. Even if someone has done it a certain way, it doesn't mean it can be made into a norm. All houses become almost individual unless everyone builds exactly the same. How air travels in a house can only be determined through careful studies over a long time, and that isn't being done currently.

Here I don't agree with you. You can absolutely compare different houses. It's also not some kind of magic how moisture in buildings behaves. It can be predicted relatively well.

It is actually true that you cannot compare houses and group all of the same type together. I have read studies where it clearly emerges that even if you take two identical houses, built from exactly the same plans, at exactly the same time, with exactly the same type of materials, the results for how these are affected differ, depending a bit on where they are located. Because the only thing that can't be the same, is where they are placed. Two houses cannot stand in exactly the same spot. Apparently, it was enough that they were placed in different cardinal directions. Then the result depends a lot on where in the country the house is. Is it near the coast? Is it inland? What are the ground conditions? How high is the house located? Is the house situated on an open field where it is windy? Or in the middle of a forest? Perhaps in the middle of other houses? If I remember correctly, the study was primarily about whether or not to have an air gap in the roof and different roof constructions.

So what is right in one place can be completely wrong in another. As for an air gap or not in cellulose insulated roofs, there is no right or wrong. An air gap can just as well add more moisture and damage the under-roof. The absence of an air gap can do the same thing, under certain conditions.

The best thing should probably be to simply follow the manufacturer's recommendations, because then at least you might be secured in terms of insurance, etc. For then you have built according to the regulations.

 

[witten]

It is actually true that you cannot compare houses and generalize them all in the same way. I have read studies where it clearly shows that even if you take two identical houses, built from exactly the same blueprints, at exactly the same time, with exactly the same types of materials, the results of how they are affected differ slightly depending on where they are located.

This is exactly what happens with risk constructions, sometimes it works and sometimes it doesn't. Modern construction techniques have eliminated most older risk constructions with the help of, among other things, slab-on-grade with underlying insulation, vapor barriers especially in the roof, as well as the entire safe water regulation. With modern recognized solutions, it's not a lottery whether it works or not; if it's not built incorrectly, it works regardless of location.

 

[tompax]

This is exactly what happens with risk constructions, sometimes it works and sometimes it doesn't. Modern building techniques have eliminated most older risk constructions with the use of foundation slab with underlying insulation, vapor barriers primarily in the roof, and the entire safe water regulations. With modern recognized solutions, it's not a lottery whether it works or not; if it's not built incorrectly, it works regardless of location.

And in that case, back to the topic about vapor brakes with wood fiber insulation:
1. Is cellulose insulation with asphalt board as wind protection and a vapor brake on the inside a "modern recognized solution"?
2. Vapor brake or vapor barrier for cellulose insulation?

The question is relevant because cellulose insulation/wood fiber insulation with all its solutions is being fully marketed today and is said to be an ecologically sound solution, good for health and everything else that is claimed.

 

[Daniel 109]

Vapor barrier is definitely a well-established method known to work. The vapor brake surely works as well. It is tight enough that not much ugliness gets into the wall.

 

[witten]

And if so, back to the topic of vapor barriers with wood fiber insulation:
1. Is cellulose insulation with asphalt board as wind protection and a vapor barrier on the inside a "modern recognized solution"?
2. Vapor barrier or vapor barrier for cellulose insulation?

The question is relevant because cellulose insulation/wood fiber insulation with all its solutions is being sold extensively today and is said to be an ecologically sound solution, good for health and everything else claimed.

Yes, I would say that both solutions apply. All insulation materials work with a wall with an air gap on the outside and a vapor barrier (or vapor brake) on the inside. That is, the material is of secondary importance from a moisture technical point of view. Then there are insulation materials that are produced with more sustainable materials, which is good from that aspect, but as you say, a lot is claimed and much cannot be backed up with sources.

The vapor brake is just a plastic that is slightly more permeable than 0.2 mm PE film. It is used where there is a risk of trapping moisture between two tight layers, such as bathroom exterior walls with an inner installation layer.. Its purpose is to let the vapor out through the wall.