Vapor tightness in inner vapor barrier with wood fiber insulation?

[ArneTW]

From an allergy perspective, it is not good to have asphalt-impregnated paper on the inside of the wall.

Ok

 

[ArneTW]

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

No, I can't say that.

However, I haven't seen any other explanation that is proven either.

It wasn't a peak of allergies but they continue to become more and more common.

/ATW

 

[Daniel 109]

Sure, you can see a connection with all development if you feel like it. Just mention something that has become more common in the latest generation, and you can point out a connection.

 

[useless]

'Hospital sickness' emerged during the 70s when, among other things, more tightly sealed houses were built. However, the problems are not due to the tightness itself, but to the introduction of many new synthetic materials such as PVC and various paints that emitted high levels of harmful substances in combination with poor ventilation, along with changed living habits where we started showering longer and more often, significantly adding more moisture to the indoor air.
Additionally, many older houses were retrofitted with 'modern' insulation despite lacking a vapor barrier, and people stopped heating with traditional methods and switched to electric heating, which impaired the previously functional natural ventilation and caused moisture in the insulation.

Nowadays, there are much lower threshold limits for how much harmful substances can be emitted, it is known that ventilation is important and that some form of diffusion barrier/brake is needed when insulating more—regardless of the material being used for insulation.

 

[postkontrollen]

Why?

There are many schools of thought on what is right and wrong. Nowadays, very well-insulated houses are being built. If moisture is built into the walls or moisture enters over time and doesn't dry out, problems arise. If a wall is too thick, the dew point can fall inside the wall, which may not dry out. If you don't have much insulation, there's a better chance that the insulation/wall will dry out. If I were to build a house with cellulose insulation, I would use a vapor brake so that the wall can absorb and RELEASE moisture and dry out. Without being an expert, I also wouldn't use plastic with, for example, mineral wool, so that these walls can also release moisture. An important aspect should be to ensure that the dew point doesn't fall inside the wall because, eventually, the load increases and moisture seeps down over time to the sill, creating problems there.

 

[useless]

An important part should be that the dew point should not end up inside the wall

The dew point always ends up inside the wall if the outside temperature is lower than the dew point for the indoor air.

 

[postkontrollen]

The dew point always ends up inside the wall if the temperature outside is lower than the dew point for the indoor air.

Yes, you are so right. The dew point just must not be too far in from the outside so that it doesn't dry up.

 

[Daniel 109]

You have obviously not understood what is called the dew point. It has nothing to do with moisture in the wall.

 

[postkontrollen]

You obviously haven't understood what is called the dew point. It has nothing to do with the moisture in the wall.

You obviously haven't read research on the subject.

 

[Daniel 109]

I have read what I have come across. But feel free to refer to research.

 

[useless]

The dew point is the temperature at which water begins to condense out of the air. If the humid air inside cannot move into the insulation, there will be no condensation.

 

[ArneTW]

The dew point is the temperature at which water begins to condense from the air. If the humid air from inside cannot move into the insulation, there will be no condensation.

I think that's how it works too...

That is, the warmer, more humid air from inside moves out into the wall, and when the temperature comes down closer to the outer wall and reaches the dew point, condensation occurs.

This has been my thought about avoiding dense layers when renovating old houses, as it results in more humid air trying to move out in fewer places, leading to more local moisture that can cause problems.

/ATW

 

[Stefan1972]

I still think one should downplay the amount of moisture that normally travels through walls........Some reason as if it's almost liters per hour.............In reality, it's probably barely measurable and that's why it normally works in most cases regardless of how one builds. In cases where there have been problems, I often think it's due to a number of factors rather than just the chosen products. Today, people use plastic because that's the customary way to build. One could probably skip the plastic many times, but it's simply easier to plastic everything.

 

[useless]

If you have proper ventilation with a slight negative pressure in the home, there will be no problems.
Since we normally use much more water in households today and often no longer have fireplaces, one cannot just rely on the fact that 'the house has stood for 150 years without problems' when renovating an old house. But unfortunately, you often hear this type of argument from typical building conservators...
New ways of living and usage require new solutions.

 

[Stefan1972]

Yes, but does anyone know how much water normally moves through the wall? No matter how much we do in today's houses, it might still be incredibly little in total. Maybe barely measurable... and in the past, maybe it was even less compared to what's increased today. Even if they were less airtight and ventilated themselves back then, what I primarily mean is that even if the load has increased, maybe the levels would still be completely manageable without plastic and without anything. I leave the department of modern airtight houses entirely as that's a different matter. Now I'm only talking about normal houses with and without plastic. From the 70s-80s onwards, houses started to be plastic-covered as a standard. Then you don't have to worry about the reality. It's there even if studies on that particular house might show it wasn't needed. But you can't do that for every building, so everything gets plastic, and it automatically creates the popular belief that you must have it, or the house will rot away... For the same reason, those who've built without it say it works perfectly, but they only see their own experiences. Someone who's torn down damages for 50 years might see something else, and someone who studies the behavior of insulation thinks another thing. In the end, very few people are familiar with the whole aspect and get involved in the entire situation of each house. Only those who build themselves with loose timbers, possibly. The super-interested types. Others build with proven methods...