Air conditioning during the renovation of an old building?

otherwise try surface cooling or chilled ceilings, but it costs several times as much

The ceiling is usually not suspended in old buildings (stucco) or is meant to be preserved, so that is ruled out.

You get used to the look of No. 2 quickly if it means you can sleep through the summer. And almost all manufacturers now offer something a bit more "stylish."

Do you have examples? I really couldn't find anything even remotely nice. At best, you can't see it at all... Something just came to mind: Is there any reason not to put a cover in front of it as long as air can flow freely in/out?

In the best case, you don't even see it...

I don't have that in store right now. ;-)

And I don't believe that any casing - like a white box? - is nicer than... well: the original, white box...

Models:
Mitsubishi Electric Style
Daikin Stylish

I guess the expensive series from almost all manufacturers are nicer than the standard models. It also depends on the HVAC technician and what they have on offer.

Do you have examples? I really couldn't find anything even remotely nice. At best, you don't see it at all... Something just occurred to me: Is there anything against putting a cover in front of it as long as the air can flow freely in/out?

Toshiba HAORI, for example, I find quite nice.

Have a look at LG Artcool. The air comes out of a picture frame there. But I have no idea if the device meets your requirements in terms of performance, etc.

And I don't believe that any covering - like a white box? - is nicer than... well: the original white box...

Well - then you can get creative :) An example: we have the original radiator covers made of wood. Or something that looks like a cabinet but has large slits for air in the right places. All looks better than some plastic things ;-)

Toshiba HAORI for example, I find quite nice.

LG Artcool

Thanks - I'll take a look at those too. But right now I'm more on the trip of putting on a nice cover. You can get something that you actually don't see or that looks original.