Facade paint: Should it be painted once or twice?

The silicone resin paint makes sense to me. Although it does not remain dirt-free over the years, it is dirt-repellent, water-repellent, and vapor-permeable. What would be a sensible alternative? Or is it about the ecological balance if I paint a few sqm of wall with it once every 15 years?

In my opinion, silicone resin paint makes sense. Although it doesn’t stay dirt-free over the years, it is dirt-repellent, water-repellent, and vapor-permeable. What would be a sensible alternative? Or is it about the ecological balance, if I paint a few square meters of wall with it once every 15 years?

A mineral paint belongs on a mineral plaster—not only because it doesn’t consist solely of chemicals and the lotus effect soon wears off—but a silicate paint. Ecological, bonded with the plaster, alkaline and thus algae-free over a very long time, also vapor-permeable and additionally moisture-regulating. The only disadvantage is that pure silicate cannot be made in strong colors. For that, dispersion silicate is needed.

But that chemical stuff, silicone resin paint, deteriorates considerably after a few years and you notice—better yet, you see—the difference.

One says this, the other that… even with colors there are quality differences and a direct comparison on a wall is not really possible/wanted ;)

One says this, the other says that... there are also quality differences in the colors, and a direct comparison on one wall is of course not possible/desirable ;)

Yes, the quality differences are with the silicone resin paints. It is more difficult to adulterate pure silicate. And if you walk through new housing developments from the 2000s, you don’t have comparisons on the same wall, but you do at many houses standing next to each other. In this respect (also due to experience in the industry) would I personally don’t put much stock in the advertising promises, but simply rely on the experience of the past hundred years. "Back then", almost only silicate paint was used. And you can tell. Dirty facades (especially in my home region Ruhr area) cannot be avoided anywhere. But the old houses have often not turned green until today. But this is just a digression. To the question of the OP: Please apply two coats.

We were not offered or discussed (prefabricated house in timber frame construction). I don’t even know how many times it was painted. I probably should have dealt with that.

Oh!? – I seem to remember it was about precisely achieving a certain shade of vanilla back then...

But the old houses have often not turned green to this day

THAT has nothing to do with the color. Walls that gently release interior warmth to the outside are rather not favored by algae. Google: algae on ETICS façades Fraunhofer Institute