Insulate basement floor

Hello everyone,

we are going to build a house with a basement. The basement will be a [weiße Wanne]. Additionally, an external insulation of 10 cm is planned. The floor in the basement should consist of 4 cm screed + underfloor heating. Our planning architect said that is sufficient. However, our sales contact thinks it makes sense to install a floor height increase of 16.5 cm for 3500€ (should serve as additional insulation). What do you think? Sensible or not?

Thanks!

Do you want to use the basement as living space? Are the 10 cm also under the basement? What kind of screed is that? At 4 cm, the necessary cover may not even be provided.

Do you want to use the basement as living space? Are the 10 cm also under the basement?

No, they are not, only on the exterior wall. The large basement room, about 35 m^2, will be a "playroom" with PlayStation and projector as well as a hobby room where we will sometimes spend evenings. But it will not be daily.

Is that even possible because of the energy saving ordinance? You are then basically heating directly into the ground. Are you sure that no insulation was planned under the screed and that you are only talking about the insulation under the slab?

I will ask again for clarification. According to the statements made today by the salesperson, only the exterior wall was planned to have insulation.