Floor construction height: KfW55, ventilation ducts, underfloor heating 150 mm

Dear forum,
unfortunately, I did not find anything suitable via the search function. If it was my user error, and there are actually entries on this topic, I would appreciate a brief note.
Otherwise, I am concerned with the following question:
For our new building KfW55, the general contractor proposes a floor structure of 190mm. An independent architect confirmed to us that he has planned and built his floor structures in the past with 150-160mm. His calculation is as follows:

[*]Concrete ceiling
[*]50mm insulation, with milled-out space within for ventilation ducts (50mm high), supply and return, fresh water and electricity
[*]Filling with perlite granulate
[*]20-30mm (impact sound) insulation
[*]20mm for underfloor heating
[*]45mm for screed
[*]15mm for covering
[*]totals 150-160mm

Since we are limited by the maximum building height, we would like to save every centimeter in the floor to add it to the room height.
Wastewater pipes will not be routed over the floor in our planning but will be routed directly in the drywall one floor below or in the basement.

Can you understand, confirm or refute the above calculation of the floor thickness based on your experience?

Thank you very much for a brief assessment from the knowledgeable members of this forum!

Have a nice Sunday
Regards
Stephan

Can you understand the above calculation of the floor thickness, confirm or refute it based on your experience?

Of course, it is technically possible as you described. But whether it is sufficient for KFW 55 is another question. You can lay the cheapest 040 EPS or high-insulating 022 PUR insulation. In the end, the energy consultant has to decide.

What kind of basement is under the described floor? Insulated or uninsulated? If uninsulated, you would need to use good insulation for 50mm thickness to be sufficient.

What kind of basement is beneath the described floor? Insulated or not insulated? If not insulated, you would need to use good insulation for 50mm thickness to be sufficient.

The basement beneath the ground floor is also insulated and heated.

Regarding the planned screed thickness of 45mm, it will not be a standard-compliant heated screed because it is too thin. Heating elements of a warm water underfloor heating system usually have a diameter of 12mm. Considering certain uncertainties, we round up to 15mm. This thickness (15mm) plus the typical screed thickness of 45mm for cement screed Ct-C25-F4 in residential construction (together 60mm) must be maintained by a cement screed. If only 45mm were actually planned, and the thickness of the heating elements is subtracted, 45mm - 12mm = 33mm would remain above the heating elements. This would be permissible with mastic asphalt. So discuss this again with the general contractor or other responsible parties and refer to DIN 18560 Part 2. That should be sufficient as an argument.
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Regards: KlaRa

Regarding the planned screed thickness of 45mm, this will not be a standard-compliant heated screed, as it is too thin.

It states 20mm for underfloor heating + 45mm screed (coverage?) = 65mm total. That would fit.

P.S. 12mm underfloor heating pipe is no longer up-to-date. Nowadays, they rather use 16mm or 17mm pipe. That also fits much better with the 20mm installation height of the underfloor heating.