ᐅ I need your help with the vapor barrier / vapor retarder.

Hello,

I attended a homebuilding fair today focused on drywall construction.
I plan to add an additional floor to an existing house or extend it.
Because I want to avoid structural issues and water ingress into the existing building during construction, I have decided to use drywall construction. (Of course, also keeping in mind that drywall = wood = healthy)

At the fair, I noticed that many manufacturers, especially the well-known ones, rely on a vapor barrier or vapor retarder.

However, I keep thinking that a vapor barrier or retarder cannot simply make moisture disappear; it must stop the water somewhere, meaning moisture will accumulate. Additionally, the walls are completely airtight. So where does the moisture go?
The vapor barrier is always installed behind the assembly where the electrician and others run their installations.

I have now done some research online and, to be honest, I am quite worried.
What I absolutely want to avoid is moisture inside the walls and the related mold growth!

According to information and horror stories, moisture and mold usually appear where vapor retarders were installed incorrectly or were damaged during installation.
I would prefer to avoid using this film altogether because my common sense tells me it cannot be good to live in a "plastic wrap."

Is it possible to forgo a vapor retarder or vapor barrier in exterior walls?
If yes, what alternatives are there?
Am I imagining things, or is this a widespread concern?

Hello, I assume you mean timber frame construction to add an additional story to your house. It is possible to omit the vapor barrier by installing OSB boards on the interior side and sealing the joints. The OSB board serves the same function as the vapor barrier. Alternatively, you can also use a climate membrane, for example, Isover Vario KM.

A solid wood wall does not require a vapor retarder either :-)

Thank you for your responses.
Unfortunately, there were not many manufacturers offering solid wood walls.
Actually, there was only one, and that was Thoma Haus.
I really liked their concept.
According to the representative, Thoma Haus is 5–10% more expensive.
However, I cannot confirm if this is true and have to take their word for it.
Why don’t well-known manufacturers offer solid wood construction?

Many manufacturers offer solid wood walls. Just search for the keyword log house ;-) Ours is even called solid wood, but in English.

But is the problem of condensation completely eliminated with solid wood?