Underfloor heating heat load calculation - simply explained?

The house is located in the Westerwald, where it used to get colder in winter (-12°C to -15°C). The calculated heating load for 100m2 of living space is just under 3.5 kW.

For comparison, since I would like to address more of your statements:
- We built according to the Energy Saving Ordinance and, according to the design, have just under 6 kW heating load for 170 sqm. Underfloor heating with gas boiler. Planned was 24cm KS + 16cm ETICS 0035. We installed 0032 ETICS.

Forget about having 24°C in the bathroom and only 18°C in the bedroom right next to the bathroom—you will achieve a maximum of 2°C temperature difference between individual rooms if at all.

Is that because of the heat pump? We have the heating in the bedroom set to 3, which results in 18 degrees, and the adjacent children's room has 22 degrees during the day and 19 at night.

Underfloor heating should be designed at max. 30°C flow temperature based on the NAT... and not 35°C

NAT = standard outside temperature? For us, that is -13 degrees. Do I understand correctly that when it is -13 degrees outside, you have a warm house with a 30-degree flow temperature? (22 in living areas and 24 in the bathroom?) I already had 37°C on the boiler at -4 degrees.

Gas boilers respond faster and can also operate at higher flow temperatures practically without significant changes in consumption. With heat pumps, it is somewhat different.

Gas boilers respond faster and can also operate at higher flow temperatures practically without major changes in consumption. With heat pumps, it's a bit different.

Ok, sorry. I didn't mean to hijack the thread. Maybe I'll start a separate thread for that. Thanks anyway

Does anyone know if a builder has a legal entitlement to the heating load calculation? We are building with a general contractor and have not received anything like that. We are simply "given" a heating system with a certain capacity. However, its capacity is included in the energy saving certificate.

Does anyone know if a builder has a legal right to the heating load calculation? We are building with a general contractor and did not receive such a thing. We are simply "presented" with a heating system of a certain capacity. However, its capacity is included in the energy saving certificate.

Depending on when you concluded the contract. From 01/01/2018 you have a right to it.

Ok thanks. Then I will ask, since I have a claim. The executing plumbing company would have to perform the calculation anyway - or do many companies just lay the heating coils as they see fit?