Gas heating capacity selection 20kW instead of 14kW

If there is KfW funding, I received a supplementary sheet for the builder from our energy consultant. It states that a room-by-room heating load calculation according to DIN 12831 should be carried out.

This results from the target temperatures of the individual rooms and the heat losses/U-values of walls and windows to determine the heating load of the entire building. In our case, it was just under 6kW heating load, and your 14kW gas heating would therefore already be oversized by a factor of 2 for us. That probably doesn’t hurt as much with gas as with a heat pump, but then choosing 20 is simply nonsense.

Is that a heating engineer or someone from the house construction company. The decisive factor today for a heating system is the smallest output, and that is far too high with the 20-size variant. If he claims he sees no problems, he either has no idea or is deliberately not telling everything.

Or there are still a few 20kW heaters in stock that need to be distributed.

Is that a heating engineer or someone from the house construction company?
What matters today with a heating system is the lowest output, and with the 20 model variant it is far too high.
If he claims he sees no problems there, he either has no idea or is deliberately not telling the whole truth.

Someone from the subcontractor of the house construction company.
I have the feeling that they have already had negative experiences because something didn't work, and therefore prefer to oversize to be sure it gets warm...

I have the feeling that they have already had negative experiences because something didn’t work, and that’s why they prefer to oversize so that it definitely gets warm...

That’s exactly it. An oversized heating system always works, even without doing the work for a detailed needs analysis. The result is then not always efficient, but the customer is warm. So they won’t complain just because the system isn’t quite as efficient as it possibly could be. Efficiency has thus been increased elsewhere – in terms of the labor input relative to the revenue generated.

If they properly calculated the heating load room by room, there would be no reason to "prefer to have a bit more heat to be warm."