Which is more sensible: heat pump or insulation?

Correctly identified, the complete external insulation (material + labor) represents a multiple of the savings.
Unless you have to renew the facade for other reasons, then the problem naturally presents itself differently.

That is precisely the problem, due to the ongoing environmental discussion, which one does not want to ignore, one is subconsciously constantly motivated to take action, even if, for example, one is completely satisfied with the facade.
Those who build new, or have to invest anyway for repair reasons, have no choice.
But there are many who (like me) are quite satisfied and have no problems.

However, they are constantly encouraged by references to… – environmental problems / saving through the use of new technology / saving the world etc. – to activate themselves and take action. Thermal insulation and airtightness are driven to heights which are demonstrably sometimes to be classified as pointless.
In the zeal of information regarding new technologies, the problem of amortization is often pushed into the background through the jungle of information – for reasons of interest by the providers. That is what I would like to hint at with the skepticism.

One should not always put financial savings in the foreground, but it is often forgotten that after the often assumed 15 years the repayment is only completed, the promised profit zone has usually evaporated by then, as the parts are already scrap again.

Perhaps I have disproportionately experienced the negative problems due to my existing skepticism, which of course shapes one.
The best was some years ago the chimney sweep’s advice to renew my oil heating system because the emissions no longer met the requirements. All information from the specialist companies also stated this.
By chance, I learned that there is a way to optimize combustion in old boilers through a simply retrofittable combustion aid and achieved 8.5% flue gas loss, thus solving the problem!
Everyone I subsequently asked about this said they had never heard of it and thought it was not possible.
Only the "Schorni", who measures, grudgingly said “astonishing” what is possible.

If there are still a few who have such a problem, they can gladly contact me via PM so that I can pass on the tip.

As already said, I am happy to also contribute my share to saving the world, but in the end, I have to pay alone, which is why I naturally always have the euro in the back of my mind. The respective retrofits ultimately eat up the amortizations, which I have to pay immediately!

Regardless of my price info on heat pumps (China), I just bought a great bargain on a small heat pump (used, because the seller had to upsize as the unit was not powerful enough – so much for the planning of specialist firms!) which I will try out for hot water use.
There I will see, measure, compare if, what, and possibly how much it brings me, and then decide whether I switch completely to a heat pump. – As the saying goes: practice makes perfect ;-)
When I have values, etc., I will post them later.

Of course, it may be exaggerated when I claim that most of the "advisors" have their own interests more in mind than optimal advice, but when you look at the offers on the internet, which for example offer free information, you will (if you are able to do your own research) quickly realize that it is only about the data (these providers are sometimes not able to give information on the topic at all)
And the "advisors" who come afterwards, I have never experienced as objective.
So thumbs up to all skeptics and keep it up; and good luck to the others and don’t forget to recalculate after 15 years but don’t forget anything!
I am aware that what I have expressed will not be the majority opinion, but the critical side should also have its say here.
That’s it, so again ---- Sorry for the long text……

But there are many who (like me) are quite satisfied and have no problems. But they are constantly encouraged by the reference to… –environmental problems / saving through the use of new technology / saving the world etc.– to activate themselves and do something.

Ah, so now we have the culprits: do-gooders and world saviors forced you against your will to start this thread. Truly, everyone is against you. It’s terrible how far the eco-dictatorship has already advanced :oops:

Ah, so now we have the culprits: do-gooders and saviors of the world forced you against your will to open this thread. Everyone is really against you. It's terrible how far the eco-dictatorship has already advanced :oops:

I read that without reproach.

I don’t want to elaborate on this further, as there are of course accurate consultants, but many (of the inexpensive ones) are de facto “pushers” who like to create problems, want to make plans, measure the heating room etc. to justify the consulting effort in order to then make corresponding offers, which are usually company-specific for commission reasons.

Wow, I would really pull that guy’s ears if he serves interests other than those of his client. Or were you a) properly informed that a third party is co-paying the fee and b) had the option to be the sole payer? My clients – although I do not do energy consulting – almost all choose the subsidized fee, where the subsidy portion is fixed and known transparently to the client. However, this also involves measures with concrete procurement, while in my opinion an energy consultant should propose manufacturer-neutral solutions.

I do not see insulation for the ground floor/basement as a loss, since for the reasons mentioned, I do not want to have a cold basement.
From years of practice, I can say that 70% goes to the ground floor and the 30% downwards are effectively a "basement ceiling heating."
In my eyes, this is not a loss.

I think you are mistaken about the dimensions.
You are now heating the entire area/volume in the basement 24/7. Just to perhaps feel 15 instead of 10 degrees comfortable for maybe 8 hours a week.

Usually, it is much more economical if you simply turn on the fan heater for those 8 hours, no matter how inefficient. That might cost you as much in those 8 hours as your underfloor heating would consume in 16 or 32 hours, but that is still better than running it for 168 hours! This is not about 20-30% efficiency, but multiples of that!

Regardless of my price info about the WP (China), I just bought myself a small heat pump at a super cheap price (used, because the seller had to upgrade since the unit did not manage enough - so much for the planning by professional companies!), which I will try out for hot water.
I will see, measure, compare whether, what, and possibly how much it brings me, and then decide whether I'll fully switch to the heat pump. –As the saying goes: Trial makes wise ;-)
When I have data etc., I will post it later.

Also a nice example, with hot water you have just chosen the area in which a heat pump operates most inefficiently! Every degree the heat pump has to cover in lift costs massively in efficiency.
You don’t need to worry about the flattening of the curve in your insulation material if you take this as your basis for forming an opinion about heat pumps.

Regarding insulation: Also calculate the U-value per euro, not based on thickness. Because your U-value per euro is what counts. A flattening efficiency curve does not consider that most of the costs are not the material, but the installation.

Overall, many of your lines of thought are not wrong, but I think you often lack an overview of the whole and especially the dimensions (which factor at which point affects what amount) are somewhat confused for you.

PS: Note down all costs that arise during your heat pump trial exactly and then calculate how much more insulation with guaranteed success you would have gotten for that.
I am also a fan of small trials like this, but most of the time it escalates extremely and is a funny little game for understanding, but economically not justifiable.

Thanks for the warnings, the thing with the basement is certainly correct for most people.
But I spend many hours (office/workshop) in the basement and use it like the ground floor. Moreover, I have an open basement staircase to the basement without doors etc.
Certainly, I could insulate some rooms better, but the "luxury" of moving down there like on the ground floor is worth it to me, which is why I am satisfied with this solution. Apparently, the basement is quite well insulated on the outside with the 36 Ytong stones, even though it protrudes 1.3 meters out of the ground because of the windows.
I have already given up on the external insulation of the ground floor as mentioned above, since the material and labor costs are much higher than the additional heating oil costs.
That was the reason for opening the thread (U-value sum Ytong + insulation). If the day comes when oil is no longer allowed to be used, it might look different again.
Even though I may seem to look at prices as a matter of principle, I am not a complete penny-pincher, so I do not see a liter of oil more or less as a problem. Regarding wall insulation, I am not a professional, which is why I have not deducted any own work and was overwhelmed by the total price.
The installation technology is no problem for me, which is also why I tried the small heat pump (it is still standing around, currently no time).
Your note on the inefficiency of the heat pump for hot water is interesting. I had already researched it, but the more I learned, the more problematic everything became.
Question why? - If I heat 10 liters of water from 20° to 40°, the heat pump needs, for example, X watts // I can measure all 3 values - temperature - kW electricity - time.
Whether I then use the water as shower water or pump it into the heating – I thought – it should be the same, right? 40° is 40°.
Perhaps I am not seeing this entirely correctly. I am always on the quick experimental side — (the heat pump barely cost me anything).
And as a small note on the skepticism: a long time ago, I was supposed to use a new control recommended by Viessmann, which would save energy!
I got such a device (modulated burner technology) once (and sold it again, because in the meantime I had repaired the old control ;)). It is always said to run fully controlled and not intervene manually. I measured exactly and logged the data – it brought nothing. In the transition period, I switch it off during the day with a timer. By "nothing" I mean, of course, more than a few liters of oil. (Just as additional info: I do not have a condensing boiler but still the old yellow burner – hence all the considerations.)
I also run the hot water in summer with electricity (partly collector) and do not run the boiler (as recommended by the professionals). I have a separate hot water boiler with a 3 kW heating rod, which heats up in the morning and then remains off. Admittedly, the water is not quite as warm in the evening, but I shower in the morning. I measured exactly and found that the additional consumption of oil was higher than the electricity. Probably the standby losses of the boiler were higher than expected. Back then I wanted to try installing a motor-operated boiler flap, as I had seen in the industry with large boilers. However, the chimney sweep banned it because it was not permitted.
Well, let's see what the hot water will cost me once I put the device into operation. Thanks to the heating rod, I can measure and compare exactly.
Since the outside temperature is already in the lower range now, and consequently the electric heating rods for heat pumps also switch on, I once asked my neighbor near me (new building without chimney! – so heat pump) to write down the electricity meter readings, as I wanted to know it concretely.
He looked at me questioningly, after which, because I didn't want to be persistent, I considered the matter closed. My suggestion to note electricity for the heat pump and electricity for the rest was answered that he does not care; he has to pay for it anyway. o_O