Substructure facade rhombus battens without insulation

Hello everyone,

to visually lighten up the entrance area, we would like to equip the facade with rhombus slats. It is an area of 5m length and 3m height.
I have already ordered the rhombus slats (untreated Siberian larch). I would simply paint them with colorless wood glaze.
The wood would be on the north side of the facade, meaning it is not exposed to sunlight. Only early in the morning does some morning sun reach it.

The facade is already plastered and painted, and behind it is the stairwell.
I want to forgo insulation as it is really only for aesthetic purposes.

Now my question is how I should make the substructure.
My plan was simply to screw a squared timber onto the facade, then staple a black diffusion-open underlay onto it, tape the seams with the appropriate tape, and then screw the rhombus profiles onto that.
Is that feasible?

What thickness of the substructure do I need at least? A squared timber of spruce 40x60 is, I think, somewhat oversized, right? Would a simple roof batten with 24x48 mm also do?

Well, the roof batten should hold if it is properly dowelled. But why the underlay membrane? Leave it out, you’ll cause condensation. The facade is ventilated at the back and fine. Regarding the color, please get advice from a specialist retailer. Larch will definitely develop a silvery-gray patina. Instead of glaze, I would look for a special oil. But please ask a professional about that.

I would have used the underlay membrane to prevent water from reaching the facade due to the gap (8mm) between the battens and to ensure the background is nicely black. Otherwise, I would have to paint the wall behind it black (it is currently white) and also paint the sub-battens black. You read everywhere that the underlay membrane should go underneath.

Okay, I will then get advice from the specialist trade regarding the treatment of the wood with glaze or oil, thanks for the information.

Yes, of course, the black one lights up, I didn’t know that. I’m not a façade builder, but foil on the outer shell, I would have concerns. That’s a question for all building physicists.

It is a diffusion-open underlay membrane as used in roof construction, so that works. Of course, you can also leave it out, but then the white facade will shine through underneath, which I do not want. I also estimate that I am well served with 24x48 impregnated spruce battens. It will be doweled to the house. I was only concerned about whether there is a minimum amount of ventilation that must be maintained for air circulation.

The underlay membrane is simply part of the desired look. Otherwise, you can see the substructure and the masonry. It also does not rest on the masonry but is attached to the battens and is therefore ventilated from behind. It protects the masonry and the airflow deters nesting pests (not 100% but it works).