Wall or roof penetrations (external/supply air): how did you install them?

Do you know if this has ever been studied anywhere or do you have some sources for your statements? Regarding the combined supply/exhaust air at the exterior wall, I found the flow diagram from Vallox convincing; with the valves above the door, they always argue with long-throw valves and the Coanda effect. However, I am not an expert in fluid mechanics and am happy to be proven otherwise...

I can only refer to my conversations with an engineer for such ventilation systems and the plans of my supplier plus the planning aids from Helios/Zehnder – these are quite simple principles.

The Coanda effect is also described there, but it is not taken as an effect that "allows" valves above the doors.

I am certainly not an expert either. I just don’t trust such isolated statements from companies that then pull such "miracle things" out of the hat, while the whole rest still plans it conventionally with two offset inlets and outlets.

Yes, that only one of the Vallox units is needed I have also seen. That is why the ventilation specialist was very skeptical, especially because of the cross-sections as well. I am now taking the thermal bridge-free one from Westaflex. Fresh air on the north and exhaust air on the south, then I will have no further roof penetrations.

I'll take photos for you tonight

That is incorrect, you only need one. The Vallox weather protection grille is for supply and exhaust air, so you could install it on your south side and wouldn't need any grille on the north side.

It has worked perfectly for us so far.

That is not incorrect.

The intended use as fresh air and exhaust air grille presupposes that:

- the system was planned that way from the start
- the two ducts lie next to each other in the wall
- the ventilation installer knows the system
- the ventilation installer cooperates.

There are simply too many "ifs" to answer the simple question about a ventilation grille. That is why I simply recommend installing two of them.

It's nice that the grille works properly for you. However, your system was specifically designed for that.

Most ventilation installers do not know the grille and convincing them otherwise is a science in itself. Alternatively, they simply do not assume any warranty.

I can only refer to my conversations with an engineer for such ventilation systems and the plans from my supplier plus the planning aids from Helios/Zehnder – these are quite simple principles.

The Coanda effect is also described there, but it is not taken as an effect that then “allows” valves above the doors.

I’m certainly not an expert either. I just don’t trust such individual statements from companies that then pull such “miracle things” out of the hat, while the rest still plan it conventionally with two offset inlets and outlets.

Our Helios system, planned by Helios, also only has a facade combination grille.