Which heat pump? Ventilation system / Air-to-water heat pump

That is the U-value of the wall, which alone is not useful. The Ht value refers to the entire envelope (including windows, doors, roof,...).

And yes, 0.28 is not exactly great - but I already suspected something like that for a single-family house with 8kW heating load.

I also believe that trench collectors would very often be possible; but you just have to bear the consequences. Delayed vegetation, risk of ground heaving/sinking, logistical challenges (always difficult when the house is in the way and the excavator can no longer reach the property, etc. etc.) – if you tinker yourself, certainly also errors in the design.

My HT with 0.25 is not much better either – but with calcium silicate bricks and clinker you can hardly do much better. I also think that insulation is an 80/20 game... arbitrarily expensive in the long run and not very effective. The great prefabricated houses with an HT of 0.15 sometimes have just as high heating costs.
For us, the hot water share will probably be around ~30%+ – there, gas would almost really have been more sensible.

What is the U-value? None was mentioned...

And it was clear that a sentence like that would come . I'm out, the guy just ignores everything.

What is the U-value? I didn't mention any...

And it was clear that such a sentence would come . I'm out, that guy ignores everything.

Then don't talk about "insulation," because I think of the U-value. Units also help to assign numerical values. Your value corresponds to an Ht value (transmission heat loss through the envelope) of 0.28 W/m²*K. That should be approximately 165 m² of living space plus the basement.

You asked me about the Ht value, I gave it to you - so don't tell me otherwise here.

Unfortunately, it's almost 250sqm of complete living space... sucks.

You asked me for the Ht value, I gave it to you – so don’t tell stories here.

Unfortunately, it’s almost 250 sqm of complete living space… stupid.

Given yes – but in combination with a wrong reference (insulation).

And regarding the square meters, you should reconsider whether my statement was really that stupid. 165 sqm plus basement -> if you assume 3 floors of identical floor area, I end up with 247.5 m² "living space". (Although even a heated basement is often not considered living space – that’s why my figure "living space" only refers to the ground floor + upper floor).