Massive construction method, Energy Saving Ordinance 2009 or KfW? Please share experiences

Hello,

...who actually calculates the consumption costs? I suspect the BU but could they ultimately manipulate (have manipulated) the numbers? Would it make sense to have them checked by an independent expert?

Both are possible, although one can certainly assume that the latter is objective and independent of sales. In the first case, both the calculation process and the result should be reviewed by a neutral expert.
The consumption costs are the second step. First, the actual demand must be determined. Consumption results in connection with the chosen technical solution.
An example for heating energy: For a building KfW EH X, a heating energy demand of 6,000 kWh/a was determined based on the structural conditions (building envelope, U-values, etc.), the climate location, and user behavior. This would result in the following consumption costs (heat pump electricity 0.16 €/kWh; E-gas 0.05 €/kWh):

Air heat pump (annual performance factor = 3.5) => 1,714 kWh/a => 275 €/a
Brine heat pump (annual performance factor = 4.5) => 1,333 kWh/a => 213 €/a
Gas condensing boiler (JNG = 0.85) => 7,059 kWh/a => 353 €/a

This then allows the respective investments to be evaluated.
The higher the demand, the more effectively the system must operate.
For heat pumps, the determined annual performance factors are of great importance. High performance factors can only be achieved if the corresponding necessary conditions are present and adhered to. This requires precise dimensioning, e.g., heating loads, heating surfaces, hydraulics, control, etc.
In practice, it happens relatively frequently that standard parameters are partially used in the calculations (window dressing), but unfortunately this is no longer noticeable in practical implementation. The consequence is poor (low annual performance factor) => higher consumption costs. In quite a few cases, the permissible system effort number is clearly exceeded, and thus the intended (purchased) efficiency status of the building is not achieved. Sometimes even the Energy Saving Ordinance requirements (e.g., primary energy) are violated. Comparable applies for gas condensing boilers regarding the JNG.
Since 2009, builders are better protected by appropriately formulated expert contractor declarations.

...Which key figures of the house or basic information are used to estimate the consumption costs?

See above!

...Shortly on the KfW:
Do I understand correctly that no normal brick (Poroton, Liapor, etc.) without additional insulation meets the KfW-70 requirement?

The respective efficiency status is determined by the entirety of the building including the system technology, not by a single component (here AW).

Best regards

... Of course, it would be possible for an energy consultant to check the calculation,..

A "quick course" for energy consultants alone is not sufficient. Additionally, an appropriate degree (TGA - Technical Building Equipment) should be available.

....but your general contractor has to provide the data and calculations.

Which calculations? Usually, apart from the certificate, they are either not available at all or do not exist.

...Whether he does this, I doubt

He would definitely and certainly be the wrong contractual partner.

Best regards.

@€uro,
thank you very much for the detailed description.
You could transfer that 1:1 into a wiki.

Speer