Heating load calculation & layout plan DIN: Is a new calculation necessary?

Just ask...

Well, as I said, he doesn't think it helps much, but he does it.

Doesn't help much either but keeps feet warm. You can clearly notice the difference whether the shower has heating loops or not.

So, the calculation was done before I decided on the ventilation system, according to the heating engineers, but it is not so important for the individual room consideration either. Rather, about 80% of the additional demand due to ventilation can be taken into account again in the total heating demand through heat recovery.

Now he doesn't want to write emails with me anymore but wants to call me during the week. For that, I want to prepare as best as possible with your help.

So what I noticed is: the heating output of the different rooms somehow doesn't match each other. In the upper floor, the bathroom only has 407 W, although it is similarly sized to children's rooms 1 & 3, which have 763 and 823 W. That probably has to do with the flow rate, which in the bathroom is only 0.9 l/min vs 1.6 and 1.7 l/min.
I suspect that this is in turn related to the higher target temperature, but how can the heating output decrease? It should actually increase, right?
Or am I completely misunderstanding something here?

: You mean it doesn't help much for the overall room temperature?

Let a professional do it like OWL, that looks like a standard invoice from a manufacturer to me. If he wants money from you anyway for the calculation, it is better to have it done by a specialist office.

No, the calculation comes from an MEP engineering office that unfortunately did not receive any specifications and therefore calculated strictly according to DIN. I still have to force the heating engineer to give an answer on whether he will accept a different plan. The new plan costs 400 EUR net, which is not exactly cheap when you can also get it for 139 EUR. I already asked him, but he did not respond to it...

So what I noticed is: The heating output of the different rooms somehow doesn't match each other. In the upper floor, the BATHROOM only has 407 W, although it is similar in size to the children's rooms 1 & 3, which have 763 and 823 W. This probably has to do with the flow rate, which in the bathroom is only 0.9 l/min vs. 1.6 and 1.7 l/min. I suspect this, in turn, is related to the higher set temperature, but how can the heating output decrease? It should rather increase, right? Or am I understanding something completely wrong? : You mean it doesn't do much for the overall room temperature?

It partly depends on how much area is covered; in K1 & 3 that is almost 40% more covered area.