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

Solid with ventilated curtain wall facade

Is not really cheap either

How about lower heating costs over the next 60 years....

save, whatever it costs From KFW 55 down to 40 is primarily more expensive technical effort. If anything, insulate to 40 level but keep the technology at 55 level.

In terms of cost, there is about 50 euros per year difference. Let it be 4 times as expensive because of CO2 tax, scarcity, and and....and then calculate your additional costs on top of that.

where exactly is the technical difference between KFW55 and KFW40?
So, heat pump and controlled residential ventilation will come anyway!

What I do officially and what not depends on whether I see if there are possibly any subsidies still available and if it’s worth it...
I believe the difference in KFW subsidies is 5000€. So if I do the insulation standard of KFW40 anyway, I could afford equipment that is 5000€ more expensive without paying a cent extra. The only question is, what is the more expensive technology?

I built KFW 55 and did not take the subsidy because I would have needed the KFW surveyor for it and the loan was unattractive. The topic is complex

If you already have a heat pump and controlled residential ventilation, you won’t need any additional technology for Kfw 40. Only from 40+ does something else get added.

Passive house is more expensive in terms of the building envelope. Floor slab, walls, windows, roof, insulation.
It makes a difference whether you choose a builder who says "well, if you insist and really want such a contraption, then we'll build it" or one who only builds KFW 40, KFW 40+ and passive houses.

Why don't you want a solid wood house?

which expensive technology makes the difference?

I believe the difference in the KFW subsidy is 5000€. So if I am going to do the insulation standard of KFW40 anyway, I could afford 5000€ more expensive technology without paying a cent for it. The question is, what is the more expensive technology?

Biomass heating system or ground-source heat pump instead of air heat pump, possibly a battery storage.

A domestic hot water circulation is then also not allowed...

If you insulate from the outside anyway, a few more centimeters don't make much difference in cost, but the technology that KfW requires for certification does.