TGA planner difficulties, underfloor heating supply temperature + wastewater ventilation

Yes, the ventilation issue should indeed be questioned.

I hope it doesn't add up, that would be really bad.

But even so, you must be aware that this heating load is really not very good for the size of the house. I'm not that deep into the topic anymore, as it's been a while for me. However, I would question the heating load again. Often it is the case that it is set too high, which then results in a plan with high flow temperatures.

There is a freely accessible tool for this if you enter the words Crink and Tool into the well-known search engine. If you have some basic data there, you can get quite far. Check whether it matches with what is assumed here. If so, in my opinion, you won't come to a 30-degree design... but something better than 40 should be possible.

The last column is unclear. Are these the ventilation heat losses now (makes little sense, as rooms are missing) or the exchange between the rooms (the hallway is also missing there...).

I calculated the last column myself. I have a document in which the supply air and exhaust air is recorded. Supply air takes place only through the specified rooms and is heated there according to my understanding. The bathrooms are missing, that is correct. The hallway only has supply air at room temperature, so I left it out.

That indicates the pressure loss.

That then depends on the length with the same pipe diameter (I see that I have incorrectly transferred data in the pressure loss on the ground floor). Accordingly, with the current design I should at least divide room 15.06 with 171 mbar into two circuits and possibly also the bathroom into two circuits so that the difference does not become so huge.

Often it is the case that this is already set too high and this then results in planning with high flow temperatures.

Unfortunately, I lack data on the U-value, so I cannot calculate it using the tool. But how is it that the tool assumes -11.3°C as the standard outdoor temperature for my location and my planner calculates with -14°C (or -16, I have to ask again)? That the heating load for such a building is very high is probably correct. I had hoped for a bit more as well. But the ventilation also really adds to it. Unfortunately, it was not financially feasible otherwise. A controlled residential ventilation system with heat recovery would have cost well over €20,000 extra and would have been planned by the same planner whom I already had no confidence in from the beginning.

Unfortunately, I am missing data on the U-value, so I cannot calculate it using the tool. But how is it that the tool assumes -11.3°C as the standard outdoor temperature for my location, while my planner calculates with -14°C (or -16°C, I need to ask again)?

Then have them give it to you. They have to be in the energy certificate anyway, so it’s no secret. Phew, as I said, for me it was 2 years ago, but I think there was an update and refinement of the standard outdoor temperature values about 3 years ago. These are the ones used for official calculations like BAFA subsidies etc. You can achieve a lot by using the search term in a search engine. There are apparently pages of an association where you can enter the postal code and the official standard temperature is displayed. The "old" temperatures were significantly lower. It sounds to me very much like the calculations were done with the old values. Basically, people like to calculate here with "safety surcharges" so that no one can complain later. But that has the consequence that you get a higher heating load, then still without ventilation and probably with a U-value that tends more towards the Building Energy Act rather than towards "55er," and that’s how you get such sizing...

Thank you for the hint. I have now found it. The temperature of -11.3° is correct here, but how is this to be interpreted? Is the planner not adhering to the current standard? Is he still allowed to use the old values? The contract states: "The heating system is designed for the coldest day according to the standard...".

And now for the practical use: Wouldn't it be the case that after moving in, I would "simply" set a lower supply temperature than the calculated one? The ratio between the rooms probably does not vary wildly. It would of course make a difference if, due to the lower heating load, a smaller heat pump could be installed. Or am I thinking too simply here?

Legally, I am not familiar with that. Essentially, you are right. If it is really only like that. But there are many who say pragmatically you don't need to calculate that much, simply everywhere a 10cm installation distance, 5cm in the bathrooms, and no circuits that are too long or of different lengths. Was this already mentioned here? What kind of heat pump is being installed? Too large is not only bad because it may be expensive, but also because the heat pump could then start short cycling and become inefficient.

I find the entire approach of the planners to be impertinent and unprofessional. But that's your problem, you are bound by it. Of course, you can and should perform a thermal balance afterwards and properly adjust the heating curve. The heating engineers usually set it to "as long as it gets warm."