ᐅ Insulating the Basement Floor Slab: Requirement for KfW 70?

Hello,
We are planning to build a single-family house this year and are considering different financing options. So far, we have not decided whether to take out a KfW loan. For a KfW 70 standard, is insulation below the basement floor slab mandatory if the rest of the house is well insulated and the heating is supplied via a district heating connection to my parents’ wood chip boiler? According to the quote, the insulation would cost us €2400 (approximately $2600). I’m wondering if this additional cost is worthwhile for a €50,000 (about $54,000) loan at a better interest rate. What do you think?

Hello,

Richis schrieb:

Is insulation beneath the basement floor slab mandatory for a KFW70 standard if the rest of the house is well insulated and the heating is supplied via a district heating connection to my parents’ wood chip boiler?

This cannot be answered generally; the specific data for the district heating must be known, which means the expert needs to perform calculations. Is it even guaranteed that you are allowed to connect there with your building project? Local authority – capacity?

Richis schrieb:

The insulation would cost €2400 according to the quote. I am wondering if the additional cost is worth it for a €50,000 loan at a better interest rate? What do you think?

Basically, it can mostly be stated that a proper building envelope – whether monolithic or with an external thermal insulation composite system (ETICS) – combined with an air-to-water heat pump will achieve KFW 70... unless the new building is planned for the Zugspitze mountain.

You can also achieve KFW 70 with the 15% rule, meaning additional insulation. Generally, insulation beneath the floor slab is mostly required from KFW 55 downwards.

Best regards, Bauexperte