Design of underfloor heating for KFW 55 house with ventilation system

Dear users,

I am unfortunately somewhat overwhelmed with whether our underfloor heating is planned correctly. The house is still in shell construction. I requested the installation plans and heating load calculations from the general contractor. The heating load was calculated according to DIN EN 12381. I have this calculation and the result from the planning office.
The installation spacing is predominantly 18 cm except in the bathrooms (once 6 cm, once 12 cm) and the utility room (24 cm). What unsettles me more, however, is the fact that in both bathrooms an undercoverage of the heating load is described ("Fehlwärme ...kW"). Additional heating devices have not yet been planned there.
May I post the planning, provided I redact personal data and the data of the planning office?

Best regards

What unsettles me more, however, is the fact that in both bathrooms an undercoverage of the heating load is described ("missing heat ...kW"). Additional heating devices are not planned there so far. May I post the plan provided I redact personal data and the planning office's data? Best regards

It's similar with us. According to the calculation, we would also have to hang a towel radiator on the wall, and the distance in our bathroom is absolutely okay. This is because we have no loops under the shower and the bathroom is rather small, thus little floor area.

It’s similar for us. According to the calculation, we would also have to hang a towel radiator on the wall, and in our bathroom the distance is absolutely fine. This is because we have no loops under the shower and the bathroom is rather small, so there is little floor area.

So that should be okay? Or could it still be optimized, for example by slightly extending the pipe length?

Attached is the plan.[ATTACH alt="IMG_20230219_093733.jpg"]78335[/ATTACH]

So having an underfloor heating in the bathroom and laying only 12cm VA is of course nonsense. Also, the very long heating circuit doesn't make much sense. Better to have more short circuits than fewer long ones. Are you fixed on the noppen system? With stapling, a closer layout should still be possible.

Overall, I find the distances very large. Are there no other possibilities to use more surface area in the bathroom and then achieve a lower flow temperature with lower VA? Do you know what minimum temperature was calculated?

Good morning,

Thank you for the response. So the outside temperature given above in the assumptions was -11 and calculations were mostly done with an adjacent temperature of -9. Did you mean these figures?
Do you mean the very long pipe in the living-dining room? I thought the pipe length here refers to the total length for both circuits there.

Could it possibly be that 12 cm is planned above in the bathroom because the distribution box is located there and therefore additional heat is already generated or space is lacking? In principle, one could at least go down to 6 cm above. Below, 6 cm is the smallest that is feasible.

Whether we have to stick with the stud system, I honestly don't know. I will make an appointment with the heating technician and first ask him for solution proposals. But I really have no idea how to argue.

So the outside temperature given above in the assumptions was -11 and most calculations were then done with an adjacent temperature of -9. Did you mean these figures?
Do you mean the very long pipe that's in the living-dining room? I thought the pipe length here refers to the total length for both circuits there

Yes, I meant those figures. But that sounds correct. With us and also occasionally here in the forum, the old standard was still used for calculations. Back then, the outside temperatures were even colder. You're right about the pipe length, I had overlooked that on my phone.

Could it possibly be that 12 cm is planned above in the bathroom because the distribution box is located there and therefore additional warmth is generated or space is lacking?

That doesn’t sound plausible to me. Having the heating circuit distributor in the bathroom certainly makes sense to have an additional heat input there, but that doesn’t reduce the laying distances. Ultimately, the main bathroom is usually the most critical room (small area, high temperature). Simply put: The more heat input possible in this room, the lower the flow temperature of the underfloor heating can be and the more efficient the heating runs (I assume a heat pump here). Solar heat input, heating circuit distributor, people, etc. are not taken into account. A certain undercoverage in the bathroom is therefore acceptable in my view.

I will make an appointment with the heating engineer and first ask him for proposed solutions.

To have a proposed solution, you first need to define a problem. Just ask about the adjustment options to improve the heating. Does the heating engineer or the planner provide the planning? In our case, the heating engineer installed the underfloor heating completely differently because he thought it was no longer up to date as planned (narrower laying distances, more heating circuits, smaller laying distances in front of the window areas). I also can’t imagine any heating engineer laying a 12 cm spacing in the main bathroom.

Please note that I don’t live in the house yet and my comments are therefore more theoretical in nature. Whether what has come out with me really works well, I still have to find out. ;)