Hello everyone,
I often read about the concept of "breathing walls."
Statements like:
- "We were told not to insulate because otherwise my 31cm (12 inch) brick wall won’t be able to breathe anymore."
- "We don’t need a ventilation system; the timber frame wall has no membrane, so it can breathe well."
- "We have a vapor-permeable wall, so moisture can escape outside, and I don’t need a ventilation system."
- "The wall is vapor-permeable, a ventilation system is not necessary, and you basically don’t need to ventilate."
I keep seeing these and similar sentences online and have even heard them personally from house building companies—the latest just this Monday. Other opinions include: Don’t put photovoltaics on the roof due to too much electromagnetic pollution. He would never install a ventilation system. Climate change? That doesn’t even exist. At some point, I just got up and left.
I’m an engineer, not involved in house building. But in my opinion, these statements make no sense at all.
A wall can never really "breathe" properly.
Here, "breathing" means a significant moisture exchange.
How is this supposed to work physically? It’s not a thin membrane, but a thick, solid wall or one filled with insulation.
Sure, a certain amount of moisture transfer always occurs. But in my view, this is absolutely negligible. There is no way that the few liters of moisture produced daily in a single-family house could pass through the wall to the outside without either a ventilation system or manual ventilation. Physically, this just can’t happen.
Of course, it’s different with older houses. They have numerous leaks that allow air and moisture exchange. But modern houses are sealed tightly. Therefore, there is no real air exchange through the walls.
And beyond the aspect of "removing moisture to the outside," there is also the aspect of "bringing fresh air into the house."
My point is not to argue for or against ventilation systems. I am in favor, but it can also work without one if you don’t want it—just with regular manual airing, in my opinion.
What do you think? Do these "breathing walls" really exist?
Am I completely wrong? Or is this myth just incredibly persistent among home builders and even building companies?
Best regards,
Specki
I often read about the concept of "breathing walls."
Statements like:
- "We were told not to insulate because otherwise my 31cm (12 inch) brick wall won’t be able to breathe anymore."
- "We don’t need a ventilation system; the timber frame wall has no membrane, so it can breathe well."
- "We have a vapor-permeable wall, so moisture can escape outside, and I don’t need a ventilation system."
- "The wall is vapor-permeable, a ventilation system is not necessary, and you basically don’t need to ventilate."
I keep seeing these and similar sentences online and have even heard them personally from house building companies—the latest just this Monday. Other opinions include: Don’t put photovoltaics on the roof due to too much electromagnetic pollution. He would never install a ventilation system. Climate change? That doesn’t even exist. At some point, I just got up and left.
I’m an engineer, not involved in house building. But in my opinion, these statements make no sense at all.
A wall can never really "breathe" properly.
Here, "breathing" means a significant moisture exchange.
How is this supposed to work physically? It’s not a thin membrane, but a thick, solid wall or one filled with insulation.
Sure, a certain amount of moisture transfer always occurs. But in my view, this is absolutely negligible. There is no way that the few liters of moisture produced daily in a single-family house could pass through the wall to the outside without either a ventilation system or manual ventilation. Physically, this just can’t happen.
Of course, it’s different with older houses. They have numerous leaks that allow air and moisture exchange. But modern houses are sealed tightly. Therefore, there is no real air exchange through the walls.
And beyond the aspect of "removing moisture to the outside," there is also the aspect of "bringing fresh air into the house."
My point is not to argue for or against ventilation systems. I am in favor, but it can also work without one if you don’t want it—just with regular manual airing, in my opinion.
What do you think? Do these "breathing walls" really exist?
Am I completely wrong? Or is this myth just incredibly persistent among home builders and even building companies?
Best regards,
Specki
D
Davidoff866 Mar 2020 09:54Thanks @Tego12.
I would prefer to leave your first paragraph about conspiracy theorists uncommented, as I think it’s a bit nonsense. I didn’t ask for "superficial" arguments, but for explanations using simplified language. In other words: Please no technical jargon.
Which you did further down, and I thank you for that. I could follow your explanations and will look into it further or check with the provider.
I could copy and paste from the Klimaholzhaus website, or you can check it yourself. I am not a building expert and, as I said, not a physicist. I find the explanation from the provider plausible. If you or others can explain with reasonable arguments why solid wood is NOT climate-regulating, I’m happy to listen. As I said, I’m open and have no problem saying: "Ah, I see? I didn’t know that. Learned something new."
I would prefer to leave your first paragraph about conspiracy theorists uncommented, as I think it’s a bit nonsense. I didn’t ask for "superficial" arguments, but for explanations using simplified language. In other words: Please no technical jargon.
Which you did further down, and I thank you for that. I could follow your explanations and will look into it further or check with the provider.
nordanney schrieb:
Let’s turn the tables for a moment. Just explain to us why a wooden wall, in contrast to a concrete wall, regulates the climate.
How does the moisture get out of the house?
I could copy and paste from the Klimaholzhaus website, or you can check it yourself. I am not a building expert and, as I said, not a physicist. I find the explanation from the provider plausible. If you or others can explain with reasonable arguments why solid wood is NOT climate-regulating, I’m happy to listen. As I said, I’m open and have no problem saying: "Ah, I see? I didn’t know that. Learned something new."
D
Davidoff866 Mar 2020 09:59Tego12 schrieb:
this needs to be secured differently (ventilation system, airing, ...).That’s a good point, by the way. Maybe regular airing is necessary instead? I’m not sure, I don’t recall the provider mentioning that. I will follow up on it.
When we visited my wife’s uncle and aunt, I never saw them open the windows (and they sometimes stayed for hours with several people there). Of course, I cannot rule out that they did it before or after. I will ask them about it.
Davidoff86 schrieb:
That is actually a good point. Maybe regular ventilation is necessary instead? I’m not sure; I can’t recall the provider mentioning that. I will follow up.
When we visited my wife’s aunt and uncle, I never saw them open the windows (and they sometimes stayed for hours with several people there). However, I can’t rule out that they do so before or after. I will ask them about it. The provider is required to give you a ventilation concept / plan.
Well, how is sufficient moisture supposed to pass through a solid wood wall? That simply cannot work physically. And as already explained, very little to no air passes through either, which is also not allowed in new constructions.
I don’t understand how anyone could come up with the idea that a significant amount of moisture exchange can take place through a solid wood wall.
Tego explained this very well.
Please copy what the manufacturer promotes on their website.
And yes, you simply have to ventilate. That’s the only way.
The disadvantages are:
- Effort (ventilating twice daily in a two-story single-family house is annoying)
- Air is still often used up (a ventilation system continuously supplies fresh air)
- Higher heat loss in winter (with mechanical ventilation with heat recovery this is not the case, but there is some electricity consumption)
I don’t understand how anyone could come up with the idea that a significant amount of moisture exchange can take place through a solid wood wall.
Tego explained this very well.
Please copy what the manufacturer promotes on their website.
And yes, you simply have to ventilate. That’s the only way.
The disadvantages are:
- Effort (ventilating twice daily in a two-story single-family house is annoying)
- Air is still often used up (a ventilation system continuously supplies fresh air)
- Higher heat loss in winter (with mechanical ventilation with heat recovery this is not the case, but there is some electricity consumption)
Modern houses are airtight, and this is tested. Breathable walls, which would ensure sufficient air exchange, would fail any blower door test.
If I remember correctly, a diffusion-open wall can compensate for about 3% of the indoor humidity produced in the house. That is too little.
If I remember correctly, a diffusion-open wall can compensate for about 3% of the indoor humidity produced in the house. That is too little.
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