Substructure facade rhombus battens without insulation

You cannot see the difference. Except that the groove and tongue profiles do not warp. You save a lot of time during installation.

I also initially had the tongue-and-groove option in mind, but then decided against it because of the price.

Intuitively, I would have now stapled the underlay membrane to the battens. This way, the rhombus battens lie tight against the underlay membrane and the wall behind can breathe. Possibly, I would have wrapped the lathing of the substructure with an additional layer of underlay membrane to protect it from moisture.
How is it done correctly then?
From what you usually find online, those without insulation have not installed an underlay membrane either.

I am facing exactly the same question. I think that if the underlay membrane lies directly against the back of the battens, there could still occasionally be the possibility that rainwater penetrates through the joints during driving rain for some reason and may not drain properly, but instead partially accumulates between the membrane and the batten, which could eventually damage the wood.

The membrane is actually vapor permeable. That way, the wall can breathe. And if rainwater hits the joints, it can drain properly. I am also unsure about my theory. I will write to a manufacturer of these membranes and ask.

You can just let me know what you found out. Tackering the foil to the battens without contact with the house wall would of course be the easiest. Then you would have to figure out how to get the foil onto the house wall with simple lathing. Nothing will surely hold there in the long run.

I need to bring the post up again.

We want to clad the front of the garage and the bay window with rhombus slats. The total wall area is about 20 m². Does anyone know roughly what one can budget for that? On the internet, it says something like 200 EUR/m² - but that surely already includes labor costs, right? I would actually like to do it myself.

Now to my actual question: Since it is clear from the outset that we want to clad these two areas with wood for aesthetic reasons, can the application of the exterior plaster be "skipped" at those spots for building physics reasons? Or does it still have to be applied for insulation purposes?

In my opinion, the exterior plaster can be omitted if the cladding is properly insulated with a facade membrane and mineral wool. Is that correct?

Does one actually "save" a significant amount by leaving out the exterior plaster on the said areas totaling about 20 m²?

well, if you want to do it yourself, then you just have to calculate how much material you need and see what the cost per m² is. It also depends on which wood you prefer... there are already quite significant price differences.

I would definitely apply an exterior plaster under the construction and also paint it with color. This way, you don't offer any easy surface for possibly penetrating water to get into the masonry. Possibly you would also create a thermal bridge yourself, that would be my assessment. And since it’s only about 20 m², I wouldn’t think about any possible savings. Here you have certainly received a m² price from your plasterer and can calculate it yourself. ;-)