KfW55 house with insulated basement? Funding - Yes/No?

Hello everyone,

we are currently planning the construction of our single-family house + basement. The house will be delivered by a prefabricated house builder with KfW55 standard. We want to have the basement constructed by a regional construction company. Now I am a bit uncertain regarding the KfW55 loan. If the basement ceiling is insulated according to KfW requirements, is the house then considered a KfW55 house? Or does the entire basement have to be insulated to meet the standard?

Maybe someone has built something similar or has informed themselves.

Thank you and best regards

Who filled out the original KFW application for you? That person must / should assess which construction measures are strictly necessary to achieve the Kfw55 standard.

We have already had topics here in the forum where KFW funds were disbursed and at the end of the construction and the KFW55 (final) confirmation there was a huge "AHA" experience and the standard was not achieved.

KfW55 then applies to the thermally sealed residential unit.
If you are insulated according to KfW55 guidelines towards the uninsulated basement, then yes, your residential unit is insulated to KfW55 standard.
The person constructing the basement should know this. And before signing the contract regarding the basement, I would record in writing that the basement has sufficient insulation to build a house above it according to KfW55 and thus achieve KfW55 overall.
Similarly, I would take this written statement (also before signing the contract) to your prefabricated house supplier and clarify with them that it is sufficient.
That way you have claims later if something doesn’t work out.