KFW 55 according to reference values

Hello,

we are planning to build a single-family house in the summer. Now we are checking whether it is economical for us to achieve KFW-55. From 1.4., the simplified verification procedure according to reference values is sufficient for Kfw funding.

Does it even make sense to use the simplified verification procedure, or is it easier to achieve with a normal calculation anyway?

For windows and other transparent parts, a Uw < 0.90 W(m2K) is required. Am I correct in understanding that this is also necessary for roof windows? So far, I have not found anything in this area?

Thanks

Cheers Tentakel

The question can basically only be answered in connection with a specific building design.

In the simplified procedure, the U-values of the heat-transferring external components are given. In the full verification procedure, a complex calculation process, the components can be related to each other and offset against one another. The balance must correspond to the values specified by the Energy Saving Ordinance or the KfW funding programs. Therefore, during the design phase for the shell construction, the planner is potentially more flexible with the full procedure and can compensate disadvantages in one area with higher insulation in another.

The simplified thermal bridge verification according to Formblatt D is also associated with design specifications and restrictions that may negatively impact the design.

Whether you want to follow the specifications of the building services engineering with the designed system packages is up to you to decide.

Basically, every structural engineer who is also listed in the dena list as a building energy consultant / energy efficiency expert already provides the complete verification with their thermal protection proof, because they have the necessary and BAFA-approved calculation program.

These options are best discussed directly at the beginning of the collaboration with the architect and structural engineer. I advocate the complete verification procedure and the greater design freedoms.