Underfloor heating heat load calculation - simply explained?

If you do not specify which temperatures you want, standard values of 20 degrees for living rooms and 24 degrees for bathrooms will be used.

Thank you for the feedback. I have just found out that theoretically, any heat pump can be specified in the BAFA application, and later in the implementation, you still receive funding if a different heat pump is used, as long as it is eligible for funding. This takes some of the time pressure off us, and we will then require a room-by-room heating load calculation.

Thanks again!

Just throwing this out there as a hint:

we ourselves have a KFW 55 house which, due to the circulation (which we absolutely wanted and rightly so) just missed the KFW 40 standard. The house is located in the Westerwald where it used to get quite cold in winter (-12°C to -15°C). The calculated heating load for 100m2 living space is just under 3.5 kW (which is still too high in reality) and our air-to-water heat pump with 3.5 kW only starts to work in a range from about 5°C outside temperature where it actually enjoys working and does not cycle.

What I want to say
(in a blunt way and assuming you want normal temperatures inside the house, max 24°C in the bathroom and 20°C-22°C in the other rooms)

Choose the heat pump that can modulate as far down as possible....

Choose the smallest possible heat pump, less is more...

Do not take an all-in-one heat pump that even integrates the ventilation system...

Do not trust the general contractor (GU), they have mixed calculations and will throw something into your house just to get it warm, they don't care if the system later heats one-to-one with electricity, because the performance factor/COP is not contractually anchored. They just have to deliver something that heats your house. You pay the monthly electricity bill, not the GU.

Forget about having 24°C in the bathroom and only 18°C right next to it in the bedroom, you will achieve at most 2°C temperature difference between rooms if at all.

Note for storage rooms or pantries: according to the Energy Saving Ordinance, no individual room control or underfloor heating is required for small rooms under 6m2.

No buffer tank

Have underfloor heating designed with a max 30°C flow temperature at NAT... and not 35°C

Keep the pipe spacing of the underfloor heating as small as possible (especially in bathrooms) and not 20cm or 25cm following the motto it has always been done that way.

Make sure that with the underfloor heating, the minimum or nominal volume flow of the heat pump is reached without any bypass valves.

Underfloor heating circuits should be as equally long as possible and have large pipe diameters, at least 16mm pipes, preferably 17mm

The connection line of the manifold in 28mm copper pipe and not in some 20mm or 25mm aluminum composite pipe nonsense

The supply lines of the underfloor heating, which are often laid centrally in the hallway, should be insulated, otherwise they heat the hallway unnecessarily and lose heat on the way to the actual room. Also, you can turn down the room temperature controller of the hallway as much as you want, but it does no good because the supply lines of the other rooms continue to give off heat (if not insulated). Our GU did not know this either until I pointed it out, so one day before the screed, the supply lines were insulated. That really hurt him because it was an extra trip, and the heating engineer had to travel an extra 100 km for one hour of work...

Well, and if you throw all that into the mix, either the GU or their heating engineer will be fed up with you and recommend you move to a level of expansion where you can contract the heating installation yourself with a company of your choice.

And yes, I am satisfied with our heating engineer and our GU even if planning the heating system was a pain...

It should also be added that in such houses the ERR is as necessary as a goiter. This causes more problems than one would like, and the supposed savings of course do not materialize but quite the opposite.

Correctly with the ERR, however, you cannot really argue this away, especially with a general contractor, because according to the Energy Saving Ordinance they are mandatory... There is an exemption application that can be submitted (before/with the building application), but usually it is too late for that when builders write to you here, as the building application has usually already been submitted or approved.

Correct about the ERR, but especially with a general contractor you won't be able to argue it away because according to the Energy Saving Ordinance they are mandatory... There is an exemption application that can be submitted (before or with the building application), but usually it is already too late when builders write to you here as the building application has mostly already been submitted or approved.

Yes, that is also the case here. I was already "aware" of that beforehand. But the WAF of the ERR is very high ;)