Compliance with the 2016 Energy Saving Ordinance with the following heating

Good day everyone,

I also have to slowly deal with the topic of heating.
Again and again I read in the forum that it is difficult for the gas boiler to comply with the new Energy Saving Ordinance 2016.

I have come up with the following concept and would like to hear your opinion on it.

General about the house:
170m² on 2 full floors + hipped roof
Exterior wall: 36.5 Ytongg PP-2 0.35 λ=0.08 U-value=0.21 W/(m²K)
no additional insulation
insulated floor slab

Heating: (prices estimated)
Gas connection = 2500€
Gas boiler 20KW = 3000€
Controlled residential ventilation + heat recovery = 8500€
Solar thermal 5m² = 6000€ ([Möglich/Sinnvoll auf einem 22° Walmdach?])
Underfloor heating = 4000 €
__________
Total price: 24000€ (price realistic?)

Would this combination make sense in your eyes, or have I made a fundamental error?

Regards
D.Gerner

20 kW?! What do you want to heat - or is this one of those moments where I misunderstand something? For us, a power requirement of 6.3 kW was calculated for 190 sqm - you do have a controlled residential ventilation system with heat recovery. I believe that the boiler including installation will rather be more expensive. Decentralized or centralized controlled residential ventilation? For centralized, I would also guess it will be more expensive. Which windows, which roof insulation, which floor insulation, which geometry? An example was once calculated with ST. The solar coverage share for heating is 10% and for hot water it is 64%. It is not entirely clear to me whether these are flat rates - but you can approach it with the help of U-Wert.net - there is a heat demand calculator there. Ultimately (without completing a study of the Energy Saving Ordinance) this can only be clarified using software - at least that is my understanding.

Controlled residential ventilation + heat recovery is currently offered by me for €12,500 including installation (and I haven't seen a cheaper price yet). I consider €8,500 to be priced too low.

Why gas?

The 20KW power was spit out to me by deine-gastherme. Seems to be a bit high.

A central ventilation system is planned.

Windows have a U-value = 0.9

There seems to be a general discussion about Gas+Solar or heat pump.
I chose gas because, as can be read in the forum, heat pumps have higher investment costs. Also, the electricity price in the future is not predictable. (Except that it steadily increases). Gas prices remained relatively constant over the years.

I have not yet dealt with the topic of insulating the floor slab and roof.
I will probably have to do that next.

Thanks for the tip for u-wert.net
I have to watch a crash course on YouTube.

You will end up building with some kind of planner anyway, right? Self-study only helps to a certain extent - without the right tools, you can only estimate. As I said... so a gas condensing boiler for 3k € is rather unrealistic - an air-water heat pump is not that far off in price from ST+gas condensing boiler+connection. Take a look at Heizungsvergleich.de, many systems are exemplary calculated there (the prices are of course only estimates and differ in real cases - in some places one can certainly question them).