New Construction KfW 55 EE: Different opinions between energy consultant and general contractor

Hello everyone,

we are currently in the final stages of planning for our KFW 55 EE single-family house (application has already been approved).

During the planning process, our general contractor provided the energy consultant with a list of components, based on which the KfW 55 EE calculation was carried out. However, the components listed are not sufficient from our energy consultant's point of view, which is why he prescribes the following changes to achieve KfW 55 EE:

[*
Ground slab
[LIST]
[*]additional insulation under ground slab XPS 100 mm


[*]Exterior walls of basement (north, east, south)


[*]Insulation: XPS 160 mm instead of EPS 120 mm


[*]Basement exterior wall (only west) + exterior walls ground floor + upper floor


[*]Aerated concrete 008 instead of 009


[*]Roof


[*]Over-rafter insulation PU 140 mm instead of under-rafter insulation 50 mm glass wool

Attached are the two component overviews from the energy consultant and the general contractor, as well as excerpts from the energy consultant’s calculation.

The general contractor now believes that the additional insulation measures are unnecessary and only result from the energy consultant having included the thermal bridges in a lump sum.

We now have the following questions:

[*]Are the components proposed by the general contractor sufficient for a KfW 55 EE house or far from the standard?
[*]Are the additional measures demanded by the energy consultant unnecessary?
[*]How much heating cost can be roughly saved by the additional insulation?
[*]Can anyone roughly estimate what the additional measures will cost?

We are simply unsure who is right with their opinion and whether it is worthwhile to pay the additional costs to have a better insulated house, or if, as the general contractor says, it is unnecessary and we should rather have the thermal bridges calculated individually...

Thanks in advance!

HausJam

we are currently in the final stages of planning for our KfW 55 EE single-family house (application has already been approved).

Which one anyway: the building application or the one for funding from the KfW?

Which one exactly: the building application or the one for funding from KfW?

Ah sorry, not quite clearly formulated. Funding from KfW.

Don't you have a fixed price with [gü]? He should implement that nicely for free;)

Don't you have a fixed price with the GÜ? He should just do it for free;)

Contract with the GÜ has not been signed yet. There were still a few issues regarding the construction service description to clarify, but the KfW application had to be submitted beforehand. Overall, it will be a fixed price, which we will finalize next Wednesday.

The relatively poor exterior walls somehow have to be compensated for; their area is simply too large. Often, only the roof and the windows remain, hence the dream values :) The question for me would rather be about the thermal bridge verification, or what kind of thermal bridge surcharge was applied at all.