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
N
nordanney6 Mar 2020 07:36You have already answered the question yourself. Old houses "breathe" through their leaks, not through their walls. Modern houses do not "breathe" at all, unless they have a ventilation system or the occupants open the windows.
Don’t hold your breath... As you said: vapor-permeable. But no one outside the construction industry really understands what that means.
In my work, I do the “counterstrapping,” but very few people can actually imagine what that is, so I explain it in a more casual, simplified way.
You just use simpler terms to describe how the components work together.
In my work, I do the “counterstrapping,” but very few people can actually imagine what that is, so I explain it in a more casual, simplified way.
You just use simpler terms to describe how the components work together.
So, I guess I’m not completely clueless yet and my reasoning still works.
But why are so many others convinced of the opposite?
For example, the architect from Monday.
Wall construction: drywall, OSB, timber frame insulated with wood wool mats, wood fiber, plaster.
He said it’s so vapor-permeable that you don’t need to ventilate at all. That’s almost criminal to spread that kind of misinformation.
Or the home builder of a friend who is currently building.
Wall construction: clay plaster with wall heating, solid wood wall, wood fiber, wooden facade.
They build without a ventilation system. According to him, it’s absolutely unnecessary.
In both cases, I see ventilating twice daily as essential to remove moisture and bring fresh air into the house. Both builders say it’s not necessary.
I really don’t get it. These are companies that have been on the market for years or even decades.
Do they just want to appear “eco-friendly” by going against common practice? Do they aim for a competitive advantage by being cheaper without controlled residential ventilation? Or do they just like to talk nonsense?
Regards,
Specki
ps: Not really an anecdote related to the topic, but still:
When we visited a home building fair, there was a company mainly building passive houses with timber frame construction. I’m generally quite interested in the “passive house system.” He talked a lot about extremely thick insulation, etc. Then I asked about the heating. He said it's all done via heating coils in the ventilation system. So in each room, there’s a small electric heater installed at the outlet. I then asked what the advantage is over KfW 40. Because the better insulation costs more money, but you save money on heating (cheaper than a heat pump with underfloor heating), so it balances out. BUT the heating energy consumption is just as high as with KfW 40, because I miss the factor of the heat pump (about 1 to 4), and I heat directly with electricity. I see absolutely no advantage there. Well, then he admitted that the operating costs are not lower than with KfW 40 and a heat pump and pretty quickly ended the conversation.
You really have to wonder if home buyers believe every bit of nonsense they hear?
But why are so many others convinced of the opposite?
For example, the architect from Monday.
Wall construction: drywall, OSB, timber frame insulated with wood wool mats, wood fiber, plaster.
He said it’s so vapor-permeable that you don’t need to ventilate at all. That’s almost criminal to spread that kind of misinformation.
Or the home builder of a friend who is currently building.
Wall construction: clay plaster with wall heating, solid wood wall, wood fiber, wooden facade.
They build without a ventilation system. According to him, it’s absolutely unnecessary.
In both cases, I see ventilating twice daily as essential to remove moisture and bring fresh air into the house. Both builders say it’s not necessary.
I really don’t get it. These are companies that have been on the market for years or even decades.
Do they just want to appear “eco-friendly” by going against common practice? Do they aim for a competitive advantage by being cheaper without controlled residential ventilation? Or do they just like to talk nonsense?
Regards,
Specki
ps: Not really an anecdote related to the topic, but still:
When we visited a home building fair, there was a company mainly building passive houses with timber frame construction. I’m generally quite interested in the “passive house system.” He talked a lot about extremely thick insulation, etc. Then I asked about the heating. He said it's all done via heating coils in the ventilation system. So in each room, there’s a small electric heater installed at the outlet. I then asked what the advantage is over KfW 40. Because the better insulation costs more money, but you save money on heating (cheaper than a heat pump with underfloor heating), so it balances out. BUT the heating energy consumption is just as high as with KfW 40, because I miss the factor of the heat pump (about 1 to 4), and I heat directly with electricity. I see absolutely no advantage there. Well, then he admitted that the operating costs are not lower than with KfW 40 and a heat pump and pretty quickly ended the conversation.
You really have to wonder if home buyers believe every bit of nonsense they hear?
D
Davidoff866 Mar 2020 08:34Hello,
we are currently planning to build a house and want to use wood as the main material.
A few weeks ago, we had an initial consultation with a carpentry company that builds with the climate wood house system from Lignotrend (solid wood) and that also built the house of my wife’s uncle 16 years ago, as well as his neighbor (a heating engineer) and a good friend of his (also built in 2005).
All of them built without a ventilation system, and the carpentry company said it is not necessary. On Lignotrend’s website, it states similarly: a ventilation system is not required, but can be installed if desired. Wood generally regulates the indoor climate by balancing temperature and humidity. The Lignotrend concept also includes solid wood walls with cavities on the inside to allow air circulation.
You can easily find detailed information online by searching for Lignotrend climate wood houses. I can only say this: we have visited my wife’s uncle many times, in winter and summer alike. The indoor climate is simply fantastic. By the way, the windows stay closed during the summer...
Best regards
we are currently planning to build a house and want to use wood as the main material.
A few weeks ago, we had an initial consultation with a carpentry company that builds with the climate wood house system from Lignotrend (solid wood) and that also built the house of my wife’s uncle 16 years ago, as well as his neighbor (a heating engineer) and a good friend of his (also built in 2005).
All of them built without a ventilation system, and the carpentry company said it is not necessary. On Lignotrend’s website, it states similarly: a ventilation system is not required, but can be installed if desired. Wood generally regulates the indoor climate by balancing temperature and humidity. The Lignotrend concept also includes solid wood walls with cavities on the inside to allow air circulation.
You can easily find detailed information online by searching for Lignotrend climate wood houses. I can only say this: we have visited my wife’s uncle many times, in winter and summer alike. The indoor climate is simply fantastic. By the way, the windows stay closed during the summer...
Best regards
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