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with us, the pipes of the Controlled Residential Ventilation on the finished precast concrete ceiling and were later integrated into the insulation for the underfloor heating.

Yes, that should also exist. Why weren’t the Controlled Residential Ventilation pipes laid on the precast concrete ceiling not yet finished with concrete like in the Selfio YouTube video (in the screenshot the concrete is just being poured over the crane and distributed on the precast concrete ceiling and the Controlled Residential Ventilation pipes)? That should actually be simpler, right?

Your different terms and also the word order rather make it complicated to understand what you mean....

I feel the same way with your descriptions at least as much WHAT haven’t you understood yet? [I’ll just check if PMs are working normally again, there was a problem last week]

with us the pipes of the controlled residential ventilation are laid on the finished precast slab [QUOTE="annab377, post: 386364, member: 50402"] The pipes of the controlled residential ventilation are laid on the precast slab,

"On the finished precast slab" is actually a contradiction in terms, because: as soon as it is finished, it is no longer precast. This type of slab is a combination of prefabrication (of the lower concrete cover and the reinforcement) and on-site fabrication (of the upper concrete cover), and after this completion it is not a bit thinner than if you had built it completely on site.

which is then filled with concrete? Call it topping concrete or in-situ concrete!?

First the "precast slab" is completed on site, as just said to the basically normally thick reinforced concrete slab. This usually happens with ready-mix concrete (= concrete transported as a flowing mixture), because in-situ concrete (produced onsite in a small drum) has gone out of fashion and is probably known only from films by my generation. Then a leveling layer for a more even surface is applied onto the structurally complete slab. This is called screed and only into this, for example, underfloor heating systems are embedded. Screeds mostly exist as wet screeds, then also using cement but without gravel – that is (simplified for laymen) the essential difference to concrete.

Our precast slab is 24 cm. Still the structural engineer did not want to have all the empty conduits in it.

Why were the controlled residential ventilation pipes not [...] laid on the precast slab which had not yet been fully concreted

In the precast slab (i.e. threaded between the spacers of the reinforcement) you lay at most lamp cables or protective conduits (which laymen like to lump together with empty conduits) – but nothing that would effectively reduce the concrete cover.

Why weren’t the controlled residential ventilation pipes installed on the prestressed concrete ceiling that had not yet been poured with concrete, like at Selfio in the YouTube video?

Well, one does it one way, another does it another way. For us, everything is placed on the prestressed concrete ceiling. This has the advantage that the ventilation technician, the installer, and the electrician can work through the finished shell construction in one go. Otherwise, we would have needed the trades for the prestressed concrete ceilings of the basement, the ground floor, and the upper floor. Best regards Axel

Well, one does it this way, another that way.

I couldn't have said it better – because: in construction, there are many things where two knowledgeable people can have completely different opinions, but the layperson understands nothing except that they are arguing. So: on the one hand, not only idiots probably do it like in the video, but (not only) I, on the other hand, would not do it. But even the topic of "round or flat ducts" (for controlled residential ventilation) itself is a broad field for a singing dispute

But why don't they also hide the empty conduits for KNX in the raw floor?

That was also one of the confusions you caused earlier: talking shortly one after another about controlled residential ventilation (ventilation ducts) and then about KNX (smart home electrical system), which apart from both starting with K, have nothing to do with each other.

P.S.: Private messages still don’t work :-(

on the one hand, thank you for your detailed answers, but on the other hand, the corona crisis must also be affecting the patience of some forum members

When I, as a future builder ( != worker from the construction industry nor architect nor civil engineer), talk about a "finished filigree slab," I assume that most people here understand that it refers to the filigree slab covered with concrete. Everything else is, in my opinion, just a matter of semantics now.

And I only came from controlled residential ventilation pipes to KNX pipes because someone happened to post photos of their KNX pipes in the ongoing discussion.

at most, lamp cables or protective conduits are laid

So what now? Is the approach by Selfio to lay the controlled residential ventilation pipes on the not yet finished filigree slab (= lower cover and reinforcement without upper cover) and then pour concrete (the upper cover) on top not anything, or – provided the structural engineer has no objection – common practice?

And I only switched from the controlled residential ventilation pipes to KNX pipes because someone happened to post photos of their KNX pipes in the ongoing discussion.

For controlled residential ventilation, I would – yes, fine, semantics again – rather speak of ducts than pipes. KNX is home automation and does not use fundamentally different installation routes than other installation systems for smart home stuff – so the same protective or empty conduits, just with different cables inside.

So what now? Is Selfio’s approach of laying the controlled residential ventilation pipes on the not yet finished filigree slab (= lower cover and the reinforcement without upper cover) and then simply embedding them with concrete (the upper cover) nothing out of the ordinary or – provided the structural engineer has no objections – common practice?

If the structural engineer is supposed to be okay with that, I see the slab becoming thicker than otherwise necessary. It seems to me that in the video example too much hollow space runs through the slab. I would probably prefer flat ducts for controlled residential ventilation, which one could, however, easily forget to wedge between the spacers, which would have to be placed on them. Viewed the other way around, round ducts are too high for installation on the raw slab to be economically viable for the total thickness. The advantage of round ducts is their flexibility – but then we are in the middle of a complex singer’s dispute. Besides, personally I am not a fan of controlled residential ventilation and would, if at all, prefer it in the decentralized variant (which is largely designed differently accordingly).