Facade discolored after 4 years

The substrate must be capable of silicification. For example, a silicone resin plaster would not be. What was used there?

For this reason, we also chose silicate paint because it has a high pH value, is nutrient-free or low in nutrients, and of course biocide-free. If I remember correctly, we also selected it because it is often used on old buildings, such as churches, etc.

Yes. However, when dealing with algal growth, you must please take into account that old masonry on the exterior wall is significantly warmer than an ETICS (the wall is "heated through" from the inside), so moisture on the outside dries very quickly again. Your exterior wall is very cold and stays damp for a long time. Therefore, many ETICS facades become "dirty" and turn green after a relatively short time. I even have something like that at an exposed location after 1.5 years because there is also no roof overhang.

Hello and thank you!

@ Tolentino
It is a system from the manufacturer Gima, it was offered to us this way upon request.

@ nordanney
Spontaneously I could understand what you mean, but when I think about it, I wonder, a field chapel or even a church are not really heated.
But be that as it may. Maybe we made a mistake when choosing. How can this be corrected? Somehow I don’t feel much like repainting every 3 years. Sure, roof overhang! But we don’t have that now (and for other reasons, I would never do it like this again).

Still, why have large (geometric) areas on the facade remained almost clean?

maybe we made a mistake in the selection.

Basically not.

Still :), why have large (geometric) areas on the facade remained almost clean?

Got lucky during processing. Wrong temperatures can lead to stiffening, for example.

when I think about it, I wonder, a field chapel or even a church is not really heated now.

Partly different materials and partly only a few degrees warmer. In the past, pure silicate was also painted. In your case - I bet on a dispersion paint.

That means the processing is actually, as I have read, demanding?

"Mineral facade paint according to DIN 18363 para. 2.4" is on the manufacturer's website, and composition:
potassium water glass, polymer dispersion, titanium dioxide,
fillers, water, polysiloxane,
film-forming aids, additives

So, the processing is actually, as I have read, demanding?

Pure silicate yes, your paint absolutely not. Roll it in and paint. Standard - emulsion paint. But maybe the temperatures were wrong.