Is KFW300 possible without QNG seal?

QNG is exactly the certificate. The life cycle analysis must be carried out, that is clear. However, the stored standard values are sufficient for everything that produces CO2. This is a pure calculation task, which in the end shows that you might choose a wooden staircase instead of a concrete staircase, or cellulose instead of mineral wool.
A QNG certification is apparently quite a different matter, since the certificates are also associated with costs, which is why one often does not get certificates for the building materials used and thus has to switch to expensive materials that actually do not have a different footprint than the non-certified ones. QNG is therefore stored in my mind as only useful for wooden houses.

QNG is therefore stored in my mind exclusively as useful for wooden houses.

Yep, since it can be represented relatively easily there through a lot of certified wood.

Yep, because it is relatively easy to represent there through a lot of certified wood.

And even there, depending on the provider, an extra 5-10k is due. This has to be checked again by an external auditor, etc. All expensive nonsense that never pays off.

And even then, depending on the provider, an extra 5-10k is charged. This has to be checked again by an external auditor, etc. All expensive nonsense that never pays off.

For the home builder, this is an expense that has no ROI.
For the provider of funding, it is a quality assurance. This creates a commercially relevant value.
You can always argue about the implementation and the costs of the design. A good system that is widely used cannot and must not be cheaper than a village agreement among buddies.

It's great that there has already been lively exchange on my question here. I would like to specify it again for our case:

We could combine the KFW300 funding with a NRW.Bank loan and would thus have an interest advantage of about €40,000 after 10 years compared to a "standard annuity loan." The funding is therefore definitely interesting at first glance in our case. We would just have to meet the criteria for KFW300, which means KFN40 house: Besides the Efficiency House 40 standard, this QNG Plus life cycle analysis must also be conducted.

Our wish is actually for a solid construction with local trades. Basically, quite a lot of necessary technology should be installed anyway (heat pump, controlled residential ventilation, large photovoltaic system with storage). However, the previous architect discussions show that apparently hardly any single-family house solid constructions as KFN40 are being implemented in this area. Everyone reacted hesitantly and has hardly any specific experience regarding feasibility/additional costs compared to "simple construction according to the Building Energy Act." Ultimately, if we want to go this route, we will probably only be able to start planning through an architect in conjunction with an energy consultant and then see where it leads.

I might need to get in touch with energy consultants and discuss the topic with them. I just want to avoid us being completely on the wrong path because the requirements may hardly be feasible or the trades may not be able to implement it properly. In that case, we could consider possibly switching to timber frame construction, where the requirements are clearly better/easier to meet.

I have the same combination (KfW 300 with NRW.Bank). In the end, it became a timber frame construction. The price compared to solid construction was similar, and NRW.Bank also provides bonuses for wood.

For local solid builders, EH40 with the simple QNG level was not a problem. For example, stone would have been a filled 36.5.