Controlled residential ventilation - Is stage 7 out of 9 an acceptable design?

Ok, then we agree that the attic decides. The planning tool sees it the same way, by the way, with the attic it no longer offers the 300 version as a choice.
Damn... So now I have the choice between buying material again, noise, or less ventilation.

We have not ventilated the attic via the [Kontrollierte-Wohnraumlüftung]. With heat recovery, that makes little sense unless it is also highly insulated! In our house, the [Kontrollierte-Wohnraumlüftung] has 3 levels (which I can program a- in intensity and b- in duration). According to the manufacturer’s calculation, there is a minimum ventilation of about 160 cbm/h, a “normal ventilation” at 230 cbm/h, and a maximum ventilation at 310 cbm/h. The house is a 1.5-story with about 165 sqm of living space. During acceptance and instruction, all air inlets and outlets were measured so that they match the values specified in the planning. Only the openings were adjusted accordingly, not the [Kontrollierte-Wohnraumlüftung] device itself! In my opinion, these systems only work if they are properly calculated, correctly installed, and accurately measured! (Air-water heat pump and [Kontrollierte-Wohnraumlüftung], etc...)

Yeah, it is highly insulated and the airtight envelope is on the outside. Of course, it has to be properly calibrated. But even if you turn the valves fully open, the pressure loss on the way to the valve doesn’t disappear. The device then has to be designed for that. With proper planning, this is the case. In our case, maybe it was calculated a bit too optimistically or the attic was not taken into account.

Hi, most common mistakes. Too small system, take the bigger one

Hi,

I wanted to report back with some practical experience after we’ve been living in the house for 8 months now.

In the summer, I operated the device at the calculated nominal power (lower in the heat). I think it was 7.5V out of a maximum of 10V. So already relatively close to the limit. Noise was audible in some rooms, but not disturbing.

Now in winter, despite humidity recovery, the air is quite dry, about 40%. I also activated the power measurement of my KNX switching actuator and was very shocked by the alleged consumption of 105 W. The actuators don’t necessarily measure very accurately, but a second look at the technical data of the controlled residential ventilation shows that the data provided there for power consumption refer to very low air resistances. So my 105 W could well be realistic. The other thing is that despite heat recovery, cool air is being blown into the house around the clock.

I have now lowered it to 5.5V, which is a bit less than the calculated "reduced" ventilation. And what can I say? At least now in winter, it is more than enough. Power consumption is down to 55W, and the system is no longer audible.

I’m curious about the next summer; hopefully it will still be sufficient then. So far, my and your concerns have certainly been unfounded. Maybe it has to do with our construction method.

It turned out not to be so brilliant to install the device in the attic. Although it is insulated, it is not only insulated from the outside but also from the living space. In any case, it cools down quite a bit over time. Currently, it’s 13 degrees. I believe this also "pre-cools" the supply air to the rooms.

Installing the device in the attic turned out not to be so brilliant after all. Although it is insulated, it's not only insulated on the outside but also towards the living space. In any case, it cools down quite a bit over time. Currently, it's 13 degrees. Because of this, I believe the supply air into the rooms is also being "pre-cooled".

That was to be expected. Despite all the opinions that it works, a controlled residential ventilation system within the heated envelope is still the best option.