Gas heating + photovoltaics possible without proof

If you can believe the energy consultant.

This is where one should start

I have already encountered a few representatives of this species and unfortunately many have little knowledge of the subject and/or no longer feel like delivering more than the standard. They can more or less operate their respective software solution and will click something together for a flat fee. But then the rule is "Doesn’t know/can’t use the software - doesn’t exist." The result is often an excess of materials when it comes to falling below certain limits ("No, we definitely need solar thermal additionally").

That’s how it was for us with the mentioned "shower pipe." That thing is apparently (still) a kind of exotic and consequently does not appear in many programs in the drop-down menu for standard solutions for renewable energies. The result: three out of four energy consultants could (or would) not consider it.
Another example were the thermal bridges (this was about the KFW funding), for which the KFW gives an incredible 4 options for consideration. However, the energy consultants always only calculated with the flat rate of 0.1 (for old buildings), everything else was considered new construction.
Or, as already mentioned, the mapping of real key figures of the system technology - too much work, so they fall back on the standard values of the DIN from 2001 (?), so on paper they are working with technology almost 20 years old.

Plan the whole thing with 36.5 cm Ytong instead of Poroton. I think then it will work out.

Ytong is not necessarily better than Poroton!

Try. You have to calculate. For us, it would have worked with a so-called [Thermobodenplatte] with gas. It was too expensive for us. Gas and solar was simply the cheapest.

Well, we have a basement anyway and were just thinking about the basement insulation.