ᐅ Is the ventilation system connected incorrectly?

A heat recovery ventilator with humidity recovery, as an additional module to a mechanical ventilation system with heat recovery, could help against dry indoor air. Some manufacturers offer this as an optional feature.

Deutsche Fertighaus Holding_2016 schrieb:
I used a smoke pen to inspect the ventilation ducts in the house.

What do you mean by ducts? You should be able to determine the airflow direction at the vents by hand without any additional tools (i.e., whether it is supply air or exhaust air).

Deutsche Fertighaus Holding_2016 schrieb:
The site manager said at the beginning that in the wet rooms (bathroom and kitchen) air is extracted, and fresh air is supplied to all other rooms.

That is not wrong but could lead to significant airflow imbalances and accordingly large volumes of air in the bathroom and kitchen. Do you have any planning documents available?

Deutsche Fertighaus Holding_2016 schrieb:
Exhaust: guest room (upper floor), office (upper floor), gallery (upper floor), dressing room (upper floor), utility room (ground floor).
Supply air: bedroom (upper floor), bathroom (upper floor), bathroom (ground floor), living room 3x (ground floor), kitchen (ground floor).
Is that correct?

In my opinion, the correct setup would be:
Supply air: guest room, office, bedroom, living room
Exhaust air: dressing room, utility room, bathroom, kitchen
The gallery could be considered a hallway, typically serving as an airflow bypass zone.

As you have it, the system is inadequate. I would report this as a defect. If you do not have the planning documents, request to see them (depending on the contract situation, you might also be entitled to obtain them, but I am not sure).

If you have the planning documents, try to balance the supplied and extracted airflow volumes.

For the time being, I would turn off the system, continue monitoring the humidity levels, ventilate manually as needed, and observe whether the headaches and eye irritation improve (keep a diary!).

We did not apply for KFW funding. I will call the company.

Is it a central or decentralized ventilation system? I assume it’s central because otherwise, not much could be done. To me, it sounds like someone in the utility room connected the two ducts the wrong way around, or the fan wheel is rotating the wrong direction.

Even if the ventilation system is running backwards, it hardly changes the indoor climate. The airflow in reverse is theoretically almost as strong as when running correctly. A ventilation system just dries out the house, which causes red eyes, scratchy throat, etc. You could try turning the ventilation system down a bit and see if the humidity increases. Usually, these systems can also be automated to run stronger during shower times and lower for the rest of the day.

You can tell if air is flowing into or out of a room by looking at the door. Modern doors are so lightweight that the airflow actually moves the door. In our bathroom, for example, the door is always pulled into the bathroom (opened). Of course, if the door catch is engaged, nothing will happen.

Payday schrieb:
new doors are so easy to move that drafts carry the door along.

Not here, I would never have expected that either. Roughly 30 m³/h (35 cubic feet per hour) through an open door (0.5 m by 1.8 m / 20 inches by 71 inches) results in an air velocity of less than 0.01 m/s (0.02 mph). Typically, air is also directed under the door through a slightly larger gap, and residents can still open the door without any effort. Your doors must be extremely easy to operate!

Hmm yeah, our doors also stay in the position they were left in.