Clinker / Dutch clinker / Hand-fired clinker

Then you can also just use impregnated bricks, we used those as well.

With a facing facade, the dew point is ALWAYS INSIDE. If the brick absorbs water, its inside also dries faster. If the brick does not absorb water, like a real clinker, then all the dew water must escape through the joints.

So every brick is also available from the factory as an impregnated version? Or does the criterion "impregnated" limit the range?

The latter would be bad for optical reasons. Then we would impregnate ourselves again.

"If the stone absorbs water, its inside also dries faster. If the stone does not absorb water, like a real clinker, then all the condensation water has to come out through the joints."

And what does that mean?

Is it good or bad that the inside dries faster? I would say good. The inside dries faster because the water "crawls" back into the stone? Does that also mean that at the dew point, i.e., inside, no condensation water forms or less than compared to normal clinkers? I would assume that neither is true.

I would expect the same behavior with "real" clinkers, with the difference that first of all, less water penetrates the stone at all, and secondly, accordingly less water has to "crawl back." According to your statement, however, this does not seem to be true.

With real clinker, the water has to come out through the joint. That means the water "crawls" back through the clinker joints or that it runs/drips down and somewhere there can flow out through ventilation openings in the joints.

Or does the latter apply mainly to clinkers that absorb more water? Or does it not apply to any variant at all?

Is one of the mentioned "crawling methods" disadvantageous with regard to efflorescence or do these only appear, if at all, in the initial period as long as not everything is dried through?

Impregnated clinker bricks are only available in limited designs, I forgot to mention that. For example, we have the Olfry 1707 Antique with factory impregnation.

Regarding the dew point: The water I mean here comes from the inside, so from the living space. Moisture diffuses through the plaster, your inner masonry, and the cavity insulation. On the cold side of the cavity insulation, so outside, this moisture condenses. If there is a lot of it, it runs down the inside of the facing bricks and out of the joints at the bottom. Normally, however, there is not that much water that it runs. Normally, the dew water is conducted outward by diffusion through the facing bricks and the joints, where it evaporates. This is, of course, an invisible process. For this scenario, a "permeable" facing brick is "better."

If the facing brick is soaked by driving rain, then it must dry in the same way. A "real clinker brick" without water absorption capacity cannot become soaked, so it would be "better" in this scenario.

Overall, this is not really a relevant issue for your selection... The "real clinker bricks" certainly have their justification in HafenCity, but you are surely not building right on the coast.