Purchase advice, heat pump comparison: Daikin or Vaillant?

With controlled residential ventilation, I then come to 6700W, without controlled residential ventilation to 8200W.

How do you come to that? Is it due to the postal code? I also took the values from the initial posting and come to different values with the same tool.

Take it to a professional... if you already read here that one should rather undersize a heat pump... maybe,

Of course, you let the professional do it. Energy performance certificate heating load calculation and specification for flow/return temperature (please toward 30/26, not higher) or room temperature. Corresponding to that, a laying plan for the underfloor heating. Oh yes. About the dimensioning. It is indeed the case that it is better to take the smaller rather than the larger variant. It has to do with technology and physics and efficiency. But you don’t understand anything about that…

Sounds quite fitting already. What kind of wall construction and so on do you have, that the HT is so poor? From which list did you get these values? Did you confuse COP with kW there? According to the manufacturer, the VWL 75/6 A still achieves 7 kW heating capacity at -7 degrees.

Wall construction is 36.5 cm insulating masonry Bisotherm (Bisoplan 10) with lambda 0.1. Floor slab 24 cm and 80 mm insulation under the screed Basement exterior walls insulated with 12 cm Styrodur Flat roof also insulated with 12 cm Styrodur The values come from the BAFA list: ...and here I wonder why the Daikins have the same performance specifications in all three sizes?!

My insignificant opinion: Whoever roughly offers a heat pump (Daikin) designed as a device for replacing old gas and oil heating systems (high heating demand) or for the construction of smaller residential complexes (= apartment buildings), would be out of the running for me due to lack of professional competence. Just saying.

Sounds quite fitting already.
What kind of wall construction and so on do you have that the Ht is so bad?

Here are the U-values for the walls:
Bisoplan 10 exterior wall to outside air: 0.257
Concrete basement wall to outside air: 0.27
Concrete basement wall to ground: 0.273
Flat roof: 0.169
Ceiling of unheated garage: 0.289
Floor slab to ground: 0.308
Partition wall inside the house to unheated rooms (garage): 0.47
Windows: 0.9

All in all, it doesn't seem too bad to me...?!

What is still unclear to me is why the Daikin heat pump in the BAFA list shows different COPs in three different sizes but lists the same heating and nominal heating capacities. On online shops, the nominal heating capacity is the same, but depending on the size, different maximum heating capacities are given:



[TH]Heat pump[/TH]
[TH]Nom. heating capacity A2/W35[/TH]
[TH]Nom. heating capacity A-7/W35[/TH]
[TH]Max. heating capacity A2/W35[/TH]
[TH]Max. heating capacity A-7/W35[/TH]

Altherma 3 H HT BG14	7.52	5.9	9.91	9.74
Altherma 3 H HT BG16	7.52	9.00	11.33	11.13
Altherma 3 H HT BG18	7.52	9.00	12.74	12.52

But what exactly do I have to consider for the design? Which performance specification can I use if I basically trust the heat load calculator from , which spit out about 7 kW in the first approach?

//Edit: The table isn’t working for me... so here is a picture:

A quick question about the garage in the basement. You write that it is unheated. Is it then also outside your thermal envelope?

This is what the basement floor plan looks like; blue=unheated, although the technical room probably won't be cold due to all the waste heat :)