Construction project - ventilation system, heating - your experiences?

TGA planner, but that costs money. Otherwise, read up on the knowledge yourself (specialist forums on building services engineering, there have been some good posts in this forum for some time) and work together with good craftsmen. They can definitely do it if you give them a few specifications.

Plan the underfloor heating with a maximum flow temperature of 30-32° based on room-by-room heat load calculation. All circuits about 80 meters, maximum 100. Avoid very small circuits. If you manage this early on, you are on a good path.

Heat pump without buffer storage.

Thank you. But I am surprised that the heating engineer does not know these "standards"? They also want to have a good reputation, so that customers are satisfied afterwards and recommend them. He must be proficient in the subject.

The heating engineers are often commissioned by the main contractors, where reputation counts little, but it must be cheap. Quick estimates and few meters of pipe.

The heating engineer I commissioned was very competent, I presented him with plans and was able to discuss them well with him. However, I do not know how he would have planned for me on his own initiative.

And if the manufacturer states that a buffer tank is mandatory, then the heating engineer will install it that way. Unless you explicitly commission it differently.

What is of no use during construction is to be surprised about anything.

And if the manufacturer says that a buffer tank is mandatory, then the heating engineer will install it that way. Unless you specifically commission it differently.

A buffer tank only makes sense with a normal heating system, but not with pure underfloor heating. Well, the general contractor basically wants to sell their contractual equipment and the unaware homeowner / buyer still ends up with the buffer tank....
I understand

The manufacturers of heat pumps partially require it. It is also somewhat understandable because individual room control is mandatory ([Energy Saving Ordinance]).

Heat pumps require flow, which is not compatible with individual room control. If all thermostats are closed, then the heat pump can charge the buffer. An alternative to the buffer are bypass valves, which should also be avoided or closed when the [ERR] is removed. It is also easier for the heating installer: with an overly warm buffer storage and individual room control, the occupants can just adjust the thermostats as usual. It gets warm and everyone is happy for the time being.

The Heizis are familiar with gas because it has been a well-known technology for decades. However, if someone now tries to simply replace heat source 1 (Gas) with heat source 2 (Wärmepumpe), the whole drama begins. That was our feeling!