Strict ventilation in a flat duct in the floor structure of the upper floor?

Dear Sir or Madam,

we still have a small problem with our planned house construction.

We currently do not know how to implement the stack ventilation in the kitchen without it interfering with our kitchen planning or causing us to be disturbed by odors around the terrace area or the later desired roof terrace on the garage roof.

Now the problem:

For us as builders, stack ventilation in the kitchen is ruled out because of the wall cabinets that are supposed to run around the entire U of the kitchen. The builder refuses to lay the stack ventilation in one of the exterior walls for static reasons.

As a solution to the problem, the builder suggested foregoing the stack ventilation and instead installing a flushing connection on the terrace, so that the drain pipe could be flushed from the terrace in case of a blockage.

We generally like the idea of the flushing opening, since fats always get into the drain in a kitchen and can settle and block the pipe.

However, we would rather not do without stack ventilation and of course would also rather not have the necessary wall projection for it in the living areas on the upper floor. For this reason, we then considered leading the stack ventilation on the opposite side of the T-wall of the kitchen into the upper floor and from there, in a flat duct such as is also used for the controlled residential ventilation, running it across the upper floor to the stack ventilation in the area of the utility room/room 4 and connecting it to its stack ventilation.

The stack ventilation in the utility room is necessary for us because we want to convert room 4 into a kitchen later, which would then also require stack ventilation.

We will also get controlled residential ventilation, but the lines for the ground floor also run within the suspended ceiling there, so these should not come into contact with the flat duct of the ventilation. However, the builder advised us against this solution because he has concerns about the stack ventilation as a flat duct in the floor structure regarding condensate and odors.

As non-experts, we are naturally uncertain about what to do, because he did not reject the implementation but advised against it.

So what do you think of the idea of laying the stack ventilation in a flat duct through the floor structure across the whole house, as an alternative to no stack ventilation at all?

So briefly summarized again:
- No wall projection in the kitchen
- Wall projection on the upper floor please only in the bathroom or room 4

I look forward to your competent advice and of course also to creative ideas for solving the problem in another way.

Attached are the construction drawings of the ground floor and upper floor. The wastewater pipes and stack ventilations are marked in red and I have marked the flat duct in the floor structure in orange.

PS: The builder is great, and I fully understand that he wants to protect himself with unknown, non-DIN-compliant procedures. All in all, it is a great construction company that only works in our region and enjoys a very, very good reputation.

The problem in this case is less the builder than us, because we have non-standard-compliant wishes.

Best regards

Jan

A vacuum ventilator may possibly be used here. In that case, no piping to the top is required. It is then sufficient if the duct system is ventilated openly above the roof at at least one point in the system.

Warm air rises, cold air falls. I consider a duct ventilation into a horizontal air column to be a faulty design, not least because the argument about condensation is convincing. Furthermore, you seem to underestimate the spring stiffness of the air column, which increases with the length of the duct (absolutely and even more so with an unfavorable ratio to the cross-section). An odor filter in an outlet under the kitchen windowsill hinders pressure equalization far less. I would consider it possible that your concept would be deemed patent-worthy by the jury of the [Schilder Geniestreichpreis].

Those who want to drive out the devil with Beelzebub should not throw the baby out with the bathwater.

Are you building with or without a basement? If without, you can do without the stack ventilation. According to DIN 1986, at least one main line connection must be extended over the roof. Alternatively, a ventilation valve can also be installed. In addition, the ventilation must be at least DN 100 and must not be reduced.

Do not build any additional ventilation piping. If the dishwasher actually sucks the trap of the sink empty, a sniff valve can still be installed in the sink cabinet. But the critical issue is mainly toilet flushes, as a completely sealed column of water rushes down the pipe in a short time and pulls the air along with it.

According to DIN, ducts from 5m are also ventilated, a cellar below does not help either