We are planning to build a house! We need experience and help.

Hello guys,
Since we have an idea about certain things, we have already informed ourselves via Aunt Google that everything is a matter of taste, we still have a few questions.
Our house should have approximately 170 sqm of living space.
Upper floor with knee wall
Without a basement
It should be a solid construction house.
We are already struggling with the bricks. But I think it depends on Ytong. Through the internet and many bricklayers we asked.
Our planner says that when building with Ytong, the current standard of thermal insulation is achieved.
Do you also think that is sufficient? Or is additional insulation not wrong despite Ytong?
It will also be plastered on the outside.

Now about the heating.
We wanted underfloor heating downstairs and in the bathroom upstairs. No heating in the bedrooms, possibly cork or something else there, plus radiators of course.
We have chosen gas and additionally want solar for hot water.
We have already decided against an air heat pump for cost reasons.
We also want to possibly have a water-based fireplace.

Our questions.
Is underfloor heating alone sufficient to heat in winter? If not, shouldn’t you rather forego it and only use radiators? If both run in the end, that is actually double costs.
In our rental apartment (25 years old), underfloor heating is not sufficient without radiators. That is why we ask if it might be due to the age.

Which gas heating system would you install?
Would you install a controlled residential ventilation system?

These are our questions at the moment.
I hope someone can help us before it starts :-)
Thanks

On the subject of heating: Underfloor heating is of course sufficient if properly dimensioned. However, one should either go entirely with radiators or entirely with underfloor heating, because different flow temperatures are necessary or accordingly large low-temperature radiators must be used.

Gas and solar with the corresponding Ytongg blocks would have worked for us as an energy saving ordinance house. Since it then became a heat pump with ground-mounted flat collectors, we achieved the Kfw70 standard. Due to the adjustment of the energy saving ordinance, I do not know whether Ytongg+Gas+Solar will still be sufficient in the future or whether controlled residential ventilation or other measures will become necessary.

Is ytong sufficient for good sound insulation? Like so you don’t hear everything outside such as shouting, playing children, etc. :-) Did you only use the ytong blocks without any additional insulation?

Better for sound insulation is certainly sand-lime brick - but if you don't live next to a railway and are not aiming for 15 cm of masonry, Ytong is probably okay too. Masons like to build with it because the stones are light :D Do you want to use facing bricks? For heating, it makes sense to use one system consistently, due to the mentioned flow temperature - what also works are large-area radiators with low temperature, wall heating, etc. Yes, underfloor heating is sufficient. We also considered a water-based fireplace - but that doesn't really fit the overall concept, it's a certain investment, and you'll have to chop wood.

We have now been living in a house made of aerated concrete for just over 3 months. I have the feeling that certain sound waves penetrate the masonry quite easily, while others less so. For example, I was startled when fireworks took place at a distance. It sounded as if one were standing outdoors. Similarly, construction vehicles are heard quite strongly. In contrast, one hears our many children in the construction area or the regular cars in the residential area quite little. Near a railway line or a main road, I would only recommend aerated concrete with additional soundproofing measures.

Good morning,

For example, I was startled when fireworks took place at a distance. It sounded as if you were standing outdoors.

That should actually not happen, because aerated concrete also comes in different densities. Denser blocks are usually used for exterior walls.

Rhineland greetings