So I still have no AC because my wife preferred a toilet renovation first and she gets priority. So I'm planning it and I want it in all rooms of my apartment, but outdoor units are only allowed to go on the balcony. So the bedrooms, on the far side of the apartment from the balcony, will need very long pipes running through the ceiling. Installers are telling me they won't do it or don't like to do it. So I've requested all the founding documentation of the building at the city archive in hopes of getting technical drawings of the building so I can see how deep the rebar is embedded in the concrete ceiling. If the rebar is >6cm deep I can dig these AC pipes in the concrete and then hopefully we're good to go! Making a little cut through horizontal structural concrete should be fine if the cut is at the bottom as the bottom is in tension and the top is in compression and when designing a building you should assume concrete has zero tension strength so my cut will be accounted for. Of course will pass this by installers and contractors too. Will look dig through this 22GB tomorrow. Or instead we'll see if Claude can find and understand pdfs with technical building drawings.