Build according to KFW 70 or the Energy Saving Ordinance 2014

according to the architect, in order to build according to the energy saving ordinance at all, we have to put solar panels on the roof.

That is not correct and your architect should know that! You can install 15% more insulation in the house instead of solar panels on the roof. Unless your house is being built at the North Pole, it should also work for you in combination with gas. Although the funds for KfW 70 these days are not much cheaper than usual annuity loans. When selling later, only the proof of the then current consumption costs counts anyway. Rhenish greetings

can you specify the 15%? is it about external insulation? because we definitely do not want to do that. but the roof etc. should of course be very well insulated. specifically: how can I comply with the [Energieeinsparverordnung] if I heat with gas.

I don't see the problem with gas and solar! The solar is only used additionally to the gas heating for water heating. I mention it because sounds as if he believes that the gas heating would be eliminated with solar.

And it is a pointless thing that practically hardly pays off - I would also oppose it

And it’s a pointless matter that hardly pays off in practice - I would also resist it

In your opinion - it is at least the cheapest alternative. But that is not the point. The OP should be fundamentally informed!

Well, you are reading something into him that I don’t see there...

It’s my opinion, but also a fact... it’s quite simple to calculate. But I don’t want to burst your bubble.