ᐅ Insulation of the top concrete floor slab of the attic in a new build

Hello,

I want to insulate the top floor ceiling in the attic of my newly built solid house. The concrete ceiling was poured about 1 year ago. Insulation between the rafters in the roof is not planned.

I have come up with the following assembly:

1. Concrete ceiling
2. Vapor barrier foil with an Sd-value > 100 m (330 ft)
3. 10 cm (4 inches) thick EPS 035 with 150 kPa
4. 10 cm (4 inches) thick EPS 035 with 150 kPa
   Note: EPS layers 3 and 4 will be installed crosswise
5. 3 cm (1 inch) thick mineral wool insulation boards 035 (intended primarily as a firestop/fire retardant)
6. Vapor-permeable membrane with a low Sd-value, (to further prevent the mineral wool insulation boards from losing fibers, which according to the manufacturer is generally not necessary with my boards) I am not sure if this is really useful. This membrane should also be installed over the entire surface.
7. 2.5 cm (1 inch) thick OSB panels fully laid with glued joints as a walkable surface over the entire floor ceiling.

What do you think of this setup?
Does it make sense from a building physics perspective?

Thanks in advance for your opinions.

You don’t need a vapor barrier with concrete. You can insulate however you want afterward.
But why insulate in new construction? The roof should already be insulated.

In new construction, the insulation should be included in the building permit / planning application.
With concrete, you don’t need a vapor barrier or fire protection; 3 cm (1.2 inches) is far too little anyway.
An uninsulated attic gets so hot and cold that hardly anything can be stored there.