Supply temperature from 40 degrees to 35 degrees "pattern" or not

The calculation is fair but at 40 degrees flow temperature a COP of 3.8 probably means that the pipe spacing is still 7.5cm and you are only increasing the flow temperature. Which does not apply to you.

Here is a table from a site where linking is not allowed just as a reference.

There are COPs from 2.6 to 4.6, mostly for brine heat pumps etc.

Too bad there is no pipe spacing included

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.. I don’t understand much about the technology, but I wonder what the point is in wanting to work with a supply temperature of 40° now, with large spacing of your underfloor heating pipes and thereby basically relying on absolutely outdated technology. I am firmly convinced that in the next 10 years, many new technical possibilities will arise in these areas. And as a homeowner, I would install my planned underfloor heating at the current optimal standard. And that is low pipe spacing to have the lowest possible supply temperatures.

Another point with higher supply temperatures is that underfloor heating systems then tend to cause floors to be partially overheated, which, as was known from the 70s to the 90s, had the disadvantage of unpleasantly “thick” feet etc.

I actually want to work with the lowest possible supply temperature, but my general contractor wants to save money (time for execution, material costs...) during the execution. But I also don't want to throw my money out the window, meaning it's strictly about economic efficiency :) .
: The average of the annual performance factor values in the screenshot is 3.8 :cool:. You're right, supply temperature info would be good.

but my general contractor wants to save money

No, he wants to squeeze more money out of you for the standard. That's a difference. It might be about 5 euros more material per square meter and one more minute of work time. Ask him to show you his calculation.

KfW55 and then with 40 degrees supply temperature. to get around the corner of the underfloor heating. We are in the year 2022! Signature signed too early!

I find 35 degrees still too high. For a new building, I would never go above 30 degrees.