ᐅ Seal ceiling penetration for ventilation

How do you seal the ceiling penetrations for ventilation ducts (installed at floor level, concrete ceiling)? With concrete or screed? Do the ducts then require any additional protection?

Fixing those things with a sound decoupling device is at least an original idea. Thanks for this humorous bedtime treat.
Styrofoam, expanding foam, and the like are actually more suitable in this case.

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11ant schrieb:

Fixing those things with a sound isolation killer is at least an original idea. Thanks for this humorous bedtime story
Styrofoam, expanding foam, and the like are actually more recommended for this.

Okay. Even for water pipes? Serious question—I’ve asked several builders, the architect, and the shell contractor, and everyone says something different (generally, about how ceiling penetrations are sealed). Here, the Styrofoam was even left inside (it was the placeholder in the precast concrete slab), and the pipes were routed through it. However, the entire opening is much too large for just those few pipes (approximately 20cm x 50cm (8 inches x 20 inches)). Is it acceptable to leave the Styrofoam in there, or does it need to be filled differently (due to sound transmission from the utility room up to the bedroom)?

I originally intended to fill our core drill holes with expanding foam.

Air masses move through ventilation ducts, which can cause the ducts to resonate. Therefore, I would avoid attaching them to other building components where their vibrations could be transmitted. In this specific case, I assume the "ducts" refer to the flat ducts of a mechanical ventilation with heat recovery system, where this issue is less pronounced. Generally, the problem arises at building component penetrations where different materials (i.e., materials with different coefficients of thermal expansion) are exposed to temperature variations: fixing them rigidly together creates compression, tension, or abrasion points, and any material placed between them initially absorbs the temperature changes. It is best to use something flexible or elastic that also prevents smoldering fires, and so on. Polystyrene is rigid but also dimensionally stable, while construction foam is suitable for the temperature (fluctuation) range on exterior walls. Which expert provides the most convincing explanation for the approach they recommend?

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Yes, these are rectangular ducts. I found expanding foam to be the most straightforward solution (and easiest to fill every small gap), and according to the specifications of a fire-resistant foam, the sound insulation is apparently quite good as well, about 59 dB. However, the architect said it would eventually break down over time and recommended using rigid foam board instead (though he couldn’t confirm how effective the sound insulation would be in that case). I find it difficult to install rigid foam without leaving large gaps.

The foam is specified for gaps up to 40 mm (1.6 inches), but a larger amount would need to be filled. (By the way, the opening is not near the exterior wall.)

Would you leave the rigid foam around the water pipes?