Pros and Cons of Ventilation and Exhaust Systems

What is wrong with dry air? -> Irritation of the mucous membranes in the nose. For infants (we currently have the second one lying around here) a humidity of 60% is best. In winter (regardless of the heating) it is naturally very difficult to achieve. Therefore, we have to humidify the air (one way or another). It is noticeable with our little one (he snores really loudly). Higher humidity would be nice for him and us.

Yes, if I always have the windows open now, do I have to turn off the ventilation or is it then pointless and only consumes electricity, right?

Yep.... as soon as a room has an open window, the calculated airflow in the house no longer works properly. However, the power consumption on the lowest setting is really not high. In summer, you turn the system off during the day anyway... in winter, it stays on until it gets too cold in the rooms at night.

A ventilation system can regulate the humidity in the house. On the one hand, it ensures that moist air is extracted. Water then condenses from the air in the system and drains away.
Result: The air becomes drier. (good in summer)
We additionally bought an enthalpy exchanger for the system. This basically works the same way, but the supply air is slightly re-moistened there.... so the dry winter air is somewhat improved.
Of course, this only works within narrow limits.... but 10% more or less makes quite a difference.

Which system do you have? I assume you do not have an enthalpy exchanger. With this, you would also have moisture recovery and it would still operate at lower temperatures without the need for a preheater. Usually, standard exchangers in systems can be replaced with an enthalpy exchanger.

What is, however, a myth, at least in my observation, is that the controlled residential ventilation heats the other rooms when the fireplace is burning. I checked this in spring... outside temperature -5°C, fireplace running at full power, supply air temperature in the system 15 degrees. But the rooms upstairs had 18 degrees room temperature.... that’s not how heating works. And if it does, the effect is minimal...

Well, but if in your case the controlled residential ventilation sucks in the warm air (heated by the fireplace) and uses up to 90% of the heat from this air to warm the supply air, then the fireplace indirectly heats the other rooms through the supply air— or am I completely missing something here?

Well, yes, but if in your case the controlled residential ventilation system sucks in the warm air (heated by the fireplace) and up to 90% of the heat from this air is used to warm the supply air, then the fireplace indirectly heats the other rooms via the supply air as well – or am I completely missing something here?

It strongly depends on the outside temperature. I gave the example from last spring. At that time, my supply air at -5 degrees outside was at 15 degrees... warmed, of course, by the fireplace that was blazing full throttle... But 15 degrees was indeed less than the current room temperature... in fact, it’s not heating but cooling. However, the air extraction is not above the fireplace, but 4 meters away in the kitchen. And I personally consider those 90% to be just marketing spin. The fact with our house (KFW55) is that waste heat is certainly used, but it is not sufficient to heat with it. You simply use less gas to heat... one can argue whether all of that is properly defined and named.

The fact with our house (KFW55) is that waste heat is certainly used, but it is not sufficient to heat with it. You simply heat less with gas.... one can argue whether all that is defined and named correctly.

OK, now I also understand what you mean.

Then I expressed myself incorrectly – I meant that the air heated by the wood stove is preheated through the controlled residential ventilation with heat recovery.

It is clear that this is not enough to fully heat.