High construction costs with rising building interest rates

Why should that not make sense? You would keep the building skeleton, which already saves valuable resources and is therefore more sensible than an immediate new build. But you can't live forever with old electrical systems (also legally, if changes are mandatory somewhere), and at some point, it doesn't help much if you only replace the old carpet to spruce up the appearance. Then you're at a full renovation, which unfortunately is often a financial loss.

What is a somewhat young house? Let's try with simple logic: We have a house with small radiators operated at a flow temperature of 60 degrees. For gas heating, that's not a problem. For the heat pump, it is, because then it is efficient. Now you really want to operate a heat pump efficiently and therefore go down to 35 degrees. Where is the heat with 25 degrees less supposed to come from? So far, 60 degrees were needed, because the radiator size was dimensioned accordingly. You can't compensate for this with less night setback, turning all radiators fully on in the house, etc. You can at most reduce the room temperature, but that greatly reduces comfort. That is your choice. No, I would go for underfloor heating. There you get at least more comfort for the renovation. Insulating the building envelope to keep the old radiators costs too much compared to the saving potential and doesn't really offer greater comfort. You can do that if the facade is anyway in terrible condition. I can understand it more for the basement and roof. The latter, however, is only done if the roof has to be redone anyway.

I’ve been through all that twice. Including electrical work, without completely gutting. Chasing slots and then plastering them up again. Then renovation felt and painting. Nothing rocket science. Screed can stay. If I absolutely want surface heating, that also works on the wall. I myself have a house from the 1960s. Walls insulated with 3cm by the previous owner. Basement ceiling and upper floor insulated by myself. Despite front door and windows from the early 90s, I manage with 40 degrees flow temperature at -11 degrees outside temperature and 21.5 degrees inside throughout the house. The radiators were not always designed for 60 degrees. Keywords that help: targeted elimination of thermal bridges and leaks, hydraulic balancing, lowering flow temperature as much as possible in 24h mode. I claim the majority of heating systems are not properly balanced. User error. Then replace radiators in a targeted manner. There are even convectors if it really can’t be done otherwise.

For me, somewhat young houses are from the mid-90s. The roof was already insulated then and the windows had values of 1.1. The electrical system is also fine. That is modern enough and still affordable. At least in Lower Saxony compared to new builds.

Yes, chasing grooves and filling them again is quite nice if you want to renew the electrical system in a single room. But what about main cables that lie in the ceiling or floor? Not always, or rather rarely, has the builder worked with empty conduits that make it easier for subsequent generations during renovations. And even this task takes a lot of time, because the wallpaper looks terrible afterward. Try doing that in the whole house as a lone wolf with family obligations.

-11 degrees? Fortunately, there is climate change. There are quite a few places (actually every German low mountain range and thus half of southern / central Germany) where -10 degrees was a standard temperature at night, and it actually dropped to -20 degrees or lower annually. Source: my own childhood / youth.

Replacing radiators selectively? How do I do that with low windows that only exist because the radiators underneath are tiny, designed for high flow temperatures? Should I clutter the rest of the wall with them? Or alternatively insulate the facade for a six-figure sum? Of course, if I buy an existing house with heating systems that were already designed for low temperatures earlier, that works. But why would one have done that broadly? It only takes valuable wall space and looks ugly. So, it doesn’t exist in the majority of existing buildings.

There is a reason why heat pumps rot in warehouses and are actually only used in new buildings. The investment is expensive and complex, and the ongoing savings have been minimal so far. Oh yes: I myself heat with a heat pump in an existing building.

Otherwise, I find a house from the mid-90s quite acceptable. Only they are not cheap and certainly not numerous. Maybe here and there in rural regions.

You will probably connect the photovoltaic system yourself as well. Oh yes, you also just remove the asbestos during the renovation and take it to the nearest recycling center. Occupational safety used to be much stricter. So were the building regulations. Just quickly building an exterior wall with thin stone was not possible in the 60s. Caution: irony.

And yes: you had to know friendly craftsmen first back then. But that was the rule because the density of craftsmen was much higher (people also knew more to do themselves on the side) and you stayed in your home village with an intact social network. That is now missing especially for those who move to the big city for the job. The further you go into the countryside, the more it still works today.

I have no personal experience with asbestos. But there have been cases in my circle of acquaintances, and yes, they disposed of it themselves in those asbestos bags. But as I said, no experience.

You can definitely install photovoltaic systems yourself. However, connecting the inverter to the grid must be done by a certified electrician.

Well, if you want a structurally and energetically poor exterior wall, you will certainly find someone to build it up. Why would I want that?

Yes, chasing grooves and filling them again is quite nice if you just want to renew the electrics in a single room. But what about main cables that lie in the ceiling or floor? Not always, or rather rarely, has the builder worked with empty conduits that make it easier for subsequent generations during renovation. And even this activity takes a lot of time because the wallpaper is also ruined afterward. Try doing that throughout the whole house as a lone wolf with family obligations.

-11 degrees? Luckily there is climate change. There are not few places (actually every German low mountain range and thus half of southern / central Germany) where -10 degrees was a standard nighttime temperature and it actually went down to -20 degrees and lower annually. Source: my own childhood / youth.

Targeted replacement of radiators? How do I do that with low windows that only exist because the radiators underneath are tiny, designed for high flow temperatures? Should I cover the rest of the wall with them? Or alternatively insulate the facade for a six-figure sum? Of course, if I buy an existing house with heating that was already designed for low temperature, that works. But why should that have been done broadly? It only takes valuable wall space and looks ugly. So it does not exist widely in existing buildings.

There is a reason why heat pumps rot away in warehouses and are basically only used in new builds. The investment is expensive and complex and the ongoing savings so far are low. Oh yes: I myself heat with a heat pump in an existing building.

Otherwise, I find a house from the mid-90s quite okay. But they are not cheap and certainly not in large numbers. Maybe here and there in rural areas.

Strange, nothing had to be replastered for me, except the bathroom. Of course, chasing grooves and filling them is possible. For example, you can create steep channels or ducts. Decommissioned chimneys work as well. Many older houses have 2-3 of the same. We're not talking about wallpapering here, those are renovations. This is about the core renovation you mentioned, down to the foundation walls, to bring a house into the current millennium. And that is possible. Without huge investment. Expensive are deep interventions in the statics etc.
And yes, there are also options for radiators. Same size, with quiet fans. Significantly reduces the flow temperature.
Heat pumps “rot away” because heating installers ask for outrageous prices. I repeat: a monoblock can be installed by an ambitious administrative clerk himself. There is plenty of help for that on the internet.

Funny, your constellation regarding house prices. That’s exactly what it is about here for the OP. Building/buying in the countryside in Lower Saxony. Best conditions to buy a good existing house at good terms.

Yes, bathroom renovation is also such a fun thing. Nicely clearing the pipes, especially when you don’t even know exactly where these pipes run in an old building. You don’t have to be a craftsman for that, but you do need a certain physical fitness, dust resistance, and above all time. Of course, you can also do without and only do the bare minimum. Then you just live at the standard from a few decades ago.

Once again: doing it yourself is great, but you also have to be realistic. What can the average person still do nowadays and how much time can be invested? Especially as a DIY beginner, you have to bring time to learn things. Unfortunately, people often only buy / renovate when time is tight, namely shortly after starting a family despite two full-time jobs. If you then have no network to fall back on, the wise sayings from various know-it-alls here in the forum won’t help you either. Above all, you have to have this knowledge BEFORE the purchase, because only then can you realistically assess the effort and possibilities when inspecting a used property.

I have no personal experience with asbestos. But there have been cases among acquaintances, and yes, they disposed of it themselves in these asbestos bags. But as I said, no experience. You can definitely install photovoltaic systems yourself. Connecting the inverter to the grid must be done by a certified electrician. Well, if you want a structurally and energetically poor exterior wall, you'll surely find someone to build it up. Why would I want that?

They probably disposed of it themselves; otherwise, the professional company would have been quite expensive. But certainly not cheap at the local recycling center.