Gas or Air-Water Heat Pump

The sad truth is that even the professionals often tend to follow the "more is better" and "more safety means fewer complaints" approach when it comes to heating dimensioning... at least that's our experience.

Now I'm just reading this... you get credited €2500 and in return, no controlled residential ventilation is installed? That's really not nice – I would install controlled residential ventilation regardless of the heating type... just the thought that at -10°C you are ventilating the expensively heated air (and with an air-water heat pump it really is expensive) out the window, because otherwise you can't regulate your humidity...

Take gas and ask again if it really should be 30 cm – it can't be, at least not Ytong.

Could be, it was written 30cm total with insulation, and a 17cm aerated concrete block with 12 cm insulation could fit, also with statics, it’s probably not a two-story building

17er aerated concrete... fine, why not - it wouldn't be my thing.

Everyone is allowed to build however they want. A matter of taste. I also have 17.5 aerated concrete and am satisfied with it. After that comes mineral wool and then very massive clinker bricks, which is something else again..

That's how I know it too - so double-shell; we also had the choice between PB or KS. But single-shell with ETICS would probably be too drafty for me.

The thermal insulation/soundproofing is somewhat weak, otherwise I don't think it is a problem as such.