Planning floor slab (insulation)

Hi guys,

besides my heating question, I am also concerned about the insulation of the floor slab.

In the attachment, I have the setup created by the energy consultant. As you can see, he suggests 5cm insulation beneath the floor slab. However, since our house (bungalow) is built on strip foundations all around, I am not really sure how sensible this is!

According to the architect, the floor slab should simply rest on the strip foundations on the compacted soil. If the insulation is applied beneath the floor slab but the strip foundations are not insulated, I don't understand the point, since they are also made of concrete; this way, the whole effect of the insulation is lost..... The site manager then said that the setup inside the house is too high for him (8cm insulation + underfloor heating), and that I should rather go for 10cm under the floor slab.

Wouldn't it be cheaper and more sensible to put the 13cm (5+8) on top of the floor slab instead? Or is there a risk of a thermal bridge here, since the masonry (36.5cm Ytong or Bisotherm) stands on the floor slab?

Maybe someone here also has the problem with strip foundations and can reassure me a bit or share their solution.

Thank you very much in advance.

Can you describe your setup to me in more detail?
Starting from the very bottom

Sand, 5cm blinding layer of lean concrete, base slab 25 cm, welding membrane, 7 cm PUR WLG 023

Thank you for the quick response. But what is this Kimmstein for?

Insulation for an uninsulated floor slab - walls are very good conductors of heat. The benefit is disputed considering the costs - especially since this is more commonly used with poorly insulating stones such as [Kalksandstein].

we are planning 36.5 cm Ytong 0.09 or 42.5 cm.