ᐅ Adding a second residential unit to the house to qualify for KfW subsidy program 153

Hello everyone,

The KfW funding program 153 has been discussed here several times, but I couldn’t find an answer to my specific question in the search. Here is the issue:

We are planning a single-family house with about 200 m² (2,150 sq ft) of living space. In the initial talks with our preferred construction company and the "seller" (timber frame construction), the idea was suggested: simply add an additional living unit on the ground floor, since then the KfW bank would provide an additional loan including a subsidy (KfW 55 house). This initially sounded great because we wouldn’t have to change our floor plan, and only needed to install a connection for a washing machine and a shower in the bathroom.

However, during further planning with the involvement of an architect, it suddenly became much more complicated. Now, separate electricity meters are required, special ceiling insulation (apparently necessary if the apartment is rented out, which we have no intention of doing), and our staircase needs to be enclosed with doors to meet F90 fire protection standards. This makes no sense to us at all, as it a) results in significant extra cost and b) these doors don’t fit into our design at all. At the bank, we had already planned to apply for the KfW loan twice. (This can be changed, but it fit well into our calculations.)

So my question is: Is it possible to obtain the KfW loan without these complex requirements? Maybe someone has had similar experiences and can offer advice – I’m grateful for any tips.

Thanks in advance, and have a nice evening everyone.