I believe many people do not know how effective air conditioning technology is.

A single portable monoblock unit with window exhaust pipe is plenty for all but the worst rooms if you target 26.5C while it is around 33C outside.

The air my portable unit emits is cooled to like ~5C.

Insulation does not even matter; the window is literally partially open. I can still cool a 70m2 room in the top floor of an ancient building, at least together with ventilating at night.

If the room was not on the top floor, or if it was only 35m2, I imagine I could comfortably cool it to 24.5 - 25C.

The only issue here is that it draws close to 1000W 24/7, it is loud, and the window has to stay open all the time.

With even just a portable split/window unit this could be much more effective and comfortable, but sadly it is not allowed for preservation reasons that make no sense.