KfW - construction: is it necessary or not?

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Much of what you write reads arbitrarily incoherent, I either cannot work out your core statements or do not find them convincing.

There will also be no efficiency increase in photovoltaics

Besides KfW55 being cheaper to build than the Energy Saving Ordinance, that is another statement I absolutely cannot understand. Since quite a few polycrystalline modules are still being installed, and the Fraunhofer ISE only opened a new photovoltaic center two years ago, I would take the opposing view here as well: There is still a lot of potential in the efficiency of photovoltaics. Both in the modules and in the inverters.

Heating pads between kfw55 and kfw70 no longer differ significantly. Usage behavior plays a bigger role here. Much of it is only theory.

Thank you for your answer to my question. Of course, everyone here asks all sorts of questions and I am happy to be interested in individual views and their backgrounds. Now it is already my 3rd house in life and in many ways I have my very own parameters. I keep noticing that some discussions are far too one-sidedly technical-calculative, but I believe that especially the behavior of the residents has the greatest impact. In 1990 I had already built a nice house with the standard of that time, and through careful energy use we were always well below comparable houses and would probably still be in the mid-range today.
I read so many standpoints and certificate designations as well as must-haves here, but I firmly believe that 95% of these sometimes hotly debated topics will not noticeably change daily life in the house; but that is what building a house is about after all.
I have lived in various houses and regions and have always made sure that I feel comfortable and use as little unnecessary energy as possible.
What I have learned in all those building times is that almost all prophecies on the subject of house building, be it value increase, cost development, technical change, mostly turned out completely differently than predicted.
Somehow I sometimes cannot imagine that some people feel perfectly comfortable in their little house after all the confusion about numbers, trends, forecasts.
What you write may be true, or maybe not, and it is the same with the other side. I do not know... but until then I use my time to feel comfortable in my house, far from subsidy frenzy, technical top performances, or expected development trends.

Make confident decisions and build how you want instead of stretching for subsidies. Build one or two sizes smaller than you could. Think about the quality of life during the years in the house instead of building for a fictional future buyer. Stay relaxed, hire local craftsmen, and enjoy the construction period. Simply don’t let others stress you about what "people" do these days while at the same time being interested in technology and processes.
It’s actually not hard.

Thank you
I see that as a good approach. I notice that every time I take a different path in building a house; precisely because each person’s life situation is different.
This time with a general contractor and hopefully more peace of mind, but a bit less freedom, and investing in the highest quality where it is important to me or brings joy, elsewhere perhaps Spartan and/or unconventional and, if possible, without any external constraints.
I am more interested in the motives than the numbers, without neglecting the latter. That is why I asked what a builder should do today.

No one can tell you an actual consumption,
because it does not exist, the user behavior would have to be the same for that.



Whoever is looking for something does not change which facts allow a factual assessment and which do not.



I am not talking about theses but facts. The efficiency of photovoltaics has been poor for decades.
Whether an investment (e.g. KfW55) is worthwhile can also be calculated. On "bauen-energie" you will find some examples
for investors. They also hold a webinar for engineers and architects, which is recognized by the chambers.
But anyone else can also participate for free.



Seen this way, everything depends on us consumers. You could not go wrong much with real estate so far.
Feeling comfortable is of course very important, but that can already depend on a neighbor.
I just wanted to point out that currently a lot here is politically determined and scientifically
not provable at all.
On the other hand, where do tax funds actually ever run back and at the same time form part of the security.
Whether now in old age or for descendants.
And of course I see myself in my job as a kind of "lawyer" for the builder vis-à-vis the institutions.

The efficiency of photovoltaics has been poor for decades.

This form of glorifying the past is exactly the main reason why the German "key technologies" are currently being overtaken from both eastern and western directions. Clearly, the efficiency of photovoltaics was modest for decades. Because there was no market pull to make significant changes to the efficiency. Area costs nothing, development and innovation, however, do. As soon as the ISE spends less than 2 years on research: bam, efficiency records are pouring in. As I said, there is still a lot of potential.

but facts.

Aha. Then prove your thesis that KfW-55 is cheaper to build than the Energy Saving Ordinance with exactly these facts. Even the KfW speaks here of ~10% additional costs. Which I can also confirm to that extent, since I had my building offered as KfW 70 (Energy Saving Ordinance), KfW 55, and KfW 40.