Purchase decision small semi-detached house 100 sqm from 1930

...dragging the lines again won't help either

I meant that the OP only redraws the walls - not everything. He knows where they are...

To bring up the topic of heating again:

My sanitary technician was on site yesterday and checked everything out.

Key statements:

You can forget about the heat pump for now, wait another 2-3 years until the market calms down.
The oil heating system is in top condition, let it keep running until then.
Underfloor heating is rather unfavorable – the cellar is not sufficiently insulated and he generally doesn’t understand why people bother to chisel out the screed instead of simply installing a ceiling heating.
Recommendation: Ceiling heating with about 6-8 cm suspension height (so about 2.45 m room height remains) – they apparently install this very often, it can be connected to a heat pump later without problems and much effort, electrical installations can be hidden and easily laid in the ceiling at the same time.

We’ll see, to me that seems quite plausible for now.

I think that is a sensible piece of advice. Our heating engineer speaks similarly. For now, we have also decided to wait and leave the gas heating in place, but we will have a tiled stove installed in the spring as an independent alternative. That is not everyone's thing, I know, but for us it's a good option. I think the heat pumps for old buildings will also make a good technological leap in the next few years. And then I'd rather buy one in a few years.

I also suspect that for people who can wait, this might be worthwhile in a few years.

Another example was the roofer who said that last year he couldn’t get insulation and the price for the available material rose from around €20 to €65 / sqm. Meanwhile, he says the price has normalized again and he’s getting the stuff thrown at him by the truckload.
However, he currently has a very hard time getting roof tiles – clay especially, but also concrete roofing is slowly becoming scarce (and very expensive).

So: we’ll put the heat pump on hold for now and the ceiling heating idea appealed to me quite a bit from the start. It does make me very suspicious that I’m being strongly advised against it here, but the plumber was convinced. Maybe it’s a matter of belief.

I think so too... like so many things. I personally don't know anyone who has a ceiling or wall heating system. They are simply hardly common, and I assume that's where the skepticism comes from.

A friend who works in the industry also told me we can calmly wait, especially with heat pumps for old buildings something will happen in the near future. So let's wait and see.

Wall heating has the disadvantage that it works best in bare rooms. When I look around, the free wall space is actually quite limited: cupboards, bookshelves, sofa, corner bench... all of that stands "in front of the heater." Besides, people also like to drill for a hanging shelf, which is basically possible but requires much more caution. You never drill into the floor. Accordingly, in new buildings, the matter is relatively clear. Regarding ceiling heating, I can't say much well-founded except that heat rises ;) and that is obviously not desired. Apart from that, it sounds like fewer disadvantages to me compared to wall heating because you don't block the ceiling and also drill into it less often.