Myth?! "Breathing Walls" What is the truth?

Hello everyone,

I keep reading about the "breathing walls."

Statements like:
- "We were told not to insulate because otherwise my 31 cm brick wall can no longer breathe"
- "We don't need a ventilation system, the timber frame wall is without foil, it can breathe well"
- "We have a diffusion-open wall, so the moisture can get outside and I don't need a ventilation system"
- "The wall is diffusion-open, a ventilation system is not required and you don't really have to ventilate"

I keep reading these and similar sentences on the internet and have even heard them personally from house-building companies. The last one just on Monday. In addition, opinions like: Don't put photovoltaics on the roof, too much electrosmog. He would never install a ventilation system. Climate change? That doesn't exist. At some point, I got up and left.

I am an engineer, have nothing to do with house construction, etc. But in my opinion, these statements are in no way comprehensible.
A wall can never reasonably "breathe."
Breathing here means a significant moisture exchange.
How is that supposed to work physically? It is not a thin membrane, but a thick massive or insulated stuffed wall.
Sure, a certain moisture exchange always takes place. But in my opinion, it is absolutely insignificant. The few liters of moisture that are produced daily in a single-family house can never get outside through the wall without a ventilation system or manual ventilation. Physically, that just cannot work.

Of course, it is different in older houses. There I have everywhere leaks through which air exchange and moisture exchange can take place. But modern houses are airtight. So no proper air exchange can happen.
And besides the aspect of "bringing moisture outside," there is also the aspect of "bringing fresh air into the house."

I am not here to argue for or against ventilation systems. I am in favor, but it also works without if you don't want one. But in my opinion, then only with regular ventilation.

How do you see it? Do these "breathing walls" exist?
Am I perhaps totally wrong? Or does this myth simply persist incredibly stubbornly in the minds of home builders up to even the house-building companies?

Regards
Specki

A wall cannot breathe, that says it all.

You 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 breathe..., You say it yourself: diffusion-open. But no one who is not in the construction industry could/can make anything of it.

In my work, I carry out the "Kontern," only a few can even imagine what that means, so colloquially I work something out in a reversed way.

You simply use simpler terms for the interaction

So, then I must not be stupid yet and my mind 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 such information.

Or the construction company of a buddy who is currently building.
Wall construction: clay plaster with wall heating, solid wood wall, wood fiber, wooden facade
Builds without a ventilation system. Absolutely not necessary, he says.

In both cases, I consider ventilating twice a day necessary to get rid of moisture and bring fresh air into the house.
Both construction companies say it's not necessary.

I really don't get it. These are companies that have been on the market for years/decades.
Do they just want to be perceived consciously as "eco" and therefore go against the current? Do they want a competitive advantage because they are cheaper without controlled indoor ventilation? Or do they simply like to talk nonsense?

Regards
Specki

ps: No anecdote, which only marginally relates to the topic:
When we were at a home building fair, there was a company that mainly builds passive houses with timber frame construction. I'm fundamentally quite interested in the "Passive House system." He talked a lot about extremely thick insulation, etc. Then I asked about the heating. He said that everything happens through heating coils in the ventilation system. So in every room, there is a small electric heater installed at the outlet. I then asked what the advantage is compared to KFW40. Because the better insulation costs more money. In return, you save money on heating (it's cheaper than a heat pump with underfloor heating), so it evens out. BUT the heating energy consumption is just as high as in KFW40 because I miss the leverage of the heat pump (about 1 to 4) and heat directly with electricity. I see absolutely no advantage there. Well, then he admitted that the running costs are not lower than those of KFW40 with a heat pump and then ended the conversation quite quickly.
You really wonder if homebuilders really let themselves be told any nonsense?

Hello, we are currently in the planning phase of construction and want to build a wooden house. A few weeks ago, we had a preliminary meeting with a carpentry company that builds with the Klimaholzhaus from Lignotrend (solid wood) and with which my wife's uncle built 16 years ago, as well as his neighbor (heating technician) and a good friend of his (also built in 2005). They all built without a ventilation system and the carpentry company also said you don’t need one. On the Lignotrend website, it says something similar: you don’t need a ventilation system, but if you want, you can install one. Wood is generally climate-regulating, meaning it regulates temperature and humidity. With the Lignotrend concept, the solid walls also have cavities inside so that air circulates. You can search the internet for Klimaholzhaus from Lignotrend, everything is explained there. I can only say one thing: we visited my wife’s uncle many times, both in winter and summer. The indoor climate is simply fantastic. By the way, in summer the windows stay closed... Best regards