Wall structure prefabricated house manufacturer diffusion-open?

Hello,
I have a question regarding the wall construction of timber frame houses.
For example, the company Allkauf Haus advertises an "unrivaled breathability" of the wall, even though rigid foam and a PE film are part of the wall construction.
Such a wall with PE film can't really breathe anymore, can it?
Thank you!
Regards
Rainer

No matter which wall construction you choose, walls do not breathe. Breathing houses come from the time when windows were still drafty. Today, a plaster can absorb a minimal amount of moisture and release it again (ideal: clay plaster), everything else is just advertising buzzwords.

We want to sell our old house and build a new house with the money, plus a small financing. Option A: Sell the old house, pay for the new house or land from that. Risk: devaluation of money between the purchases? Option B: Short-term financing (if such a thing exists) + build new house, then sell old house Option C: ???

For example, the company advertises with "unmatched breathability" of the wall,

I interpret the current situation as "the new plot is not even secured yet" - that would be a very wrong time to commit to a construction method or even a specific provider (I almost said general contractor, but that would not apply for a self-builder). Design should not come before the plot, contractor selection not before the design. Why build a new house at all?

I interpret the current situation as "new plot is not secured yet" - that would be a very wrong time to commit to a construction method or even a specific provider (I almost said general contractor, but that would not be the case for a build-it-yourselfer). Design not before the plot, contractor selection not before design. Why a new house at all?

Yes, true, the plot is not final yet... clear that a decision comes only when you have a valid development plan. The old house has become too big for me...