New construction - gas heating and controlled residential ventilation - without solar?

For gas without solar plus controlled residential ventilation, you will need a correspondingly well-insulated exterior wall to comply with the energy saving ordinance.

Only a professional can calculate that. What speaks against solar? It is probably cheaper than elaborate insulation

The arguments against solar (thermal) are 1. a relatively unfavorable cost/benefit ratio and 2. the fact that about half of all thermal solar systems function inadequately or not at all after some time. Homeowners often do not notice this and mostly save on professional inspection/maintenance. I have about 20 years of professional experience in this field... Very good thermal insulation of the building - if not overpriced - saves energy costs in the long run.

Thank you very much for your answers/opinions. I have contacted our architect. If other people have experiences/opinions on the subject, I would be happy if you share them with me.

I had a first consultation with a GU the other day. I was actually on the same page as the TE, as the energy saving ordinance is enough for me. And I always had in mind that it is also cheaper than an air-water heat pump. However, the GU said that nowadays the heat pump is overall cheaper than gas + solar. That confused me a bit and unfortunately I can't assess whether that is true or just sales tactics. I will see what other providers will tell me about it.

That depends: A good heat pump, brand factory Junkers/Viessmann or similar, is significantly more expensive than a good condensing boiler from the same manufacturer plus the two solar panels on the roof. However, you still have to pay for the gas connection, which would be unnecessary with the air-water heat pump. Find out its price from the gas supplier. Here, unbeatable cheap at 700,- all inclusive. When calculating operating costs, much depends on the assumptions about gas prices/electricity prices. That is always somewhat uncertain. The fact is: With an air-water heat pump, electricity consumption increases significantly. After all, you don't buy any gas. But the system does have this compressor running on electricity plus an electric heating rod for cold nights. The gas heating, on the other hand, uses little electricity for its control technology. Joedreck knows more precisely. Contact him. Karsten