ᐅ Single-family house U-values: Good or not so much?

Hello,

Nutshell schrieb:
Since a KfW 55 house was ordered turnkey, this is of course confirmed in writing ;-)

This is often the case on paper, but when you look more closely in practice, it can sometimes become unclear.

Nutshell schrieb:
...The primary energy demand depends on the chosen heating system,...

Not only that, the thermal quality of the building envelope also plays a role. Therefore, two parameters must be met for the respective KfW efficiency levels. Theoretical primary energy is of secondary importance for the occupant; what matters to them is the final energy consumption considering the actual conditions of the specific construction project, not the standardized parameters of the energy saving regulation!
Therefore, it is not permitted to size heating systems based on the energy saving regulation or KfW results, nor to make consumption statements on that basis!

Nutshell schrieb:
..., I don’t really find that so cool :/

Whether “cool” is a suitable criterion for a significant investment decision is something everyone has to judge for themselves ;-)

Best regards

ypg schrieb:
For me, it has always been that at, for example, 55, you only use 55 out of 100 of primary energy for that particular house.

Replace energy with primary energy. That is a significant difference, especially when it comes to what you ultimately pay 😉

DerBjoern schrieb:
...Replace energy with primary energy. This is a significant difference, especially when it comes to what you ultimately pay for 😉

In my opinion, the economic relevance of primary energy-based definitions in energy saving regulations or KfW efficiency levels has been inadequately communicated or presented to individual building owners. Whether this was intentional or not, I will leave open ;-)
What matters most to each building owner is always the payable, actual final energy consumption—not a theoretical construct of "primary energy" on paper!
The existing definitions, mind you based on primary energy, only allow for a qualitative assessment. Energy saving regulation standard is acceptable; KfW 70 is somewhat better; KfW 55 or 40 are progressively better!
That primary energy factors serve as a market policy lever, possibly influenced by lobbying, will not have escaped savvy builders ;-)
From an economic perspective, anyone building a passive house in the Upper Rhine region is just as misguided as someone constructing an energy saving regulation standard building on the Zugspitze peak 🙂
Achieving a theoretical KfW status does not automatically guarantee economic feasibility for the individual construction project, especially since many projects in practice often significantly diverge from the "paper form." The one who suffers the most is usually the inexperienced builder, who often takes on heavy debt.
Retroactive "correction" is rarely possible and usually only with limited success.
Preventing problems early on is therefore always more cost-effective than attempting repairs afterward!

Best regards