ᐅ Floor construction with ventilation system on the upper floor

Hello,

for our planned single-family home (urban villa, 2 stories without a basement), which will be built by a developer, we want to install a mechanical ventilation system with heat recovery. The ventilation installer would like to use oval ducts measuring 115x51mm (4.5x2 inches) in diameter. These ventilation ducts are intended to be installed within the floor structure of the upper floor, between the concrete slab and the screed. The floor structure currently looks like this:
- 1.0 cm (0.4 inches) surface covering
- 6.5 cm (2.6 inches) cement screed CT-C25-F4 with fibers S65 H45
- 10.0 cm (4 inches) impact sound insulation
- 18.0 cm (7 inches) reinforced concrete slab C20/25

Now the construction manager has expressed concerns and says the floor structure needs to be raised by 4 cm (1.6 inches), which would increase costs by around 1200 euros.

If I understand correctly, the ventilation ducts (5.1 cm (2 inches) in height) would have sufficient insulation both above and below (within the 10.0 cm (4 inches) impact sound insulation). I have illustrated this in the attached image. Is there something fundamentally wrong here?

Thank you for your advice.

He is probably concerned that the screed might flex along the ducts when walking on it.

Mechanical ventilation with heat recovery installed on a raw floor approximately 6cm (2.5 inches) thick, followed by 6cm (2.5 inches) of insulation (or more if calculated accordingly), then 6-7cm (2.5-2.75 inches) of screed, and finally the floor covering.
There are regulations for laying flat ducts to prevent them from collapsing (I believe the minimum spacing is 30cm (12 inches) between them).

We have
25 cm (10 inches) solid wood
9 cm (3.5 inches) loose fill insulation
6 cm (2.5 inches) screed
Floor covering

Inspected and approved by the expert.

Ventilation ducts are placed on top of the wooden ceiling.

haydee schrieb:
We have
25 cm (10 inches) solid wood
9 cm (3.5 inches) loose fill insulation
6 cm (2.5 inches) screed
Floor covering

Approved by the expert.

Ventilation ducts are placed directly on the wooden ceiling

So in your case, the ducts are directly on the ceiling, meaning on the solid wood without any insulation underneath and only insulation/loose fill above?

Alex85 schrieb:
Mechanical ventilation system installed on raw subfloor about 6cm (2.4 inches), then 6cm (2.4 inches) insulation (or more if calculated accordingly), followed by 6-7cm (2.4-2.8 inches) screed, and finally the floor covering.
There are regulations for installing the flat ductwork to prevent them from collapsing (I believe the minimum spacing is 30cm (12 inches) side by side).

I don’t fully understand this construction setup.
Which regulation needs to be considered here?
Thank you!