KFW40 or better in solid construction, possible without additional insulation?

How about lower heating costs over the next 60 years.... KFW55 is actually out of the question for me. Rather in the other direction, namely towards passive house standard in terms of insulation.

That is complete nonsense, you are harming the environment, your wallet, and your nerves!

That's complete nonsense, you are harming the environment, your wallet, and your nerves!

That's your opinion. I see it a bit differently.

With KFW55 I have a heating energy demand of 35 kWh/m²
With KFW40 only 25 kWh/m²
With Passive House only 15 kWh/m²

That means that over many decades I need only 71% or even 42% of the heating energy.

So, if I don't have a thinking error here, then I find that it already makes a huge difference.

That may look like a big difference on paper. In reality, you just save a little bit from your already necessarily very low heating demand. As I said, calculate it for yourself, it simply isn't worth it.

With KFW55 I have a heating demand of 35 kWh/m²
With KFW40 only 25 kWh/m²
With Passive House only 15 kWh/m²

This means that over many decades I only need 71% or even 42% of the heating energy.

Only on paper. You can also have higher heating costs in a KfW40 house than in a 55 house. This is only theory based on technical data and a calculation. Real life often looks different.

Yes, that's how it is, you can't base it on bare numbers in that area anymore. Financially, you can calculate that amortization is excluded. It harms the environment because you have excessive resource consumption, whether EPS or mineral wool or something else. And the risk in construction increases because very meticulous work must be done on sealing and co.

Better do KFW55, controlled residential ventilation, photovoltaics, and geothermal energy. That does good, even if it takes a long time to amortize.

For KFW55 I have a heating demand of 35 kWh/m²
For KFW40 only 25 kWh/m²
For Passive House only 15 kWh/m²

This means that over many decades I only need 71% or even 42% of the heating energy.

Even if I took the most noble, most expensive and most universal form of energy, namely electricity, that would be at 26 cents/kWh

For KFW55 9.1 euros/m²
For KFW40 6.5 euros/m²
For Passive House 3.9 euros/m²

So a difference of 5.2 euros/m². For 140 m² that would be around 700 euros. But how much more are you allowed to
a) spend once,
b) pay more in maintenance?

Your actually used heating energy will be significantly cheaper per kWh than electricity – the calculation therefore shifts accordingly to your disadvantage.