Ventilation system in the new building, yes or no?

... I am an engineer and understand enough about thermodynamics to realize that heat recovery makes sense.

The question is whether one understands "makes sense" as functionality or economic viability. Operating the ventilation system of a restaurant (on the Zugspitze) without heat recovery would probably hardly be economically sensible. For a single-family house with an average outdoor temperature of 10°C during the heating period, this would probably not be profitable. I think this is now clear. It simply depends on the energy balances.

... General consensus on controlled residential ventilation: Super comfortable, but if it is not available, airing also works, if you are not too lazy to do it.

I share the first opinion, the second, as already mentioned, only under certain conditions!

... Name a few factors that speak for and against it.

The necessities are partly explained, among other things, in DIN 1946-6.

... What other factors are there?

For example: Location => ambient noise, cooling with nocturnal outdoor air in summer! Here, window ventilation would only be suitable in a clearly quiet location! The energy saving ordinance has led to some problems regarding summer thermal insulation in exposed locations, especially in attics.

... The heat losses through warm air are the same when airing as with controlled residential ventilation without heat recovery, as long as the walls are not allowed to cool down when airing.

But only if the air exchange is absolutely identical.

..., why some think it cannot work without it.

It is always a matter of perspective. Those who use the comfort and can and want to pay for it will hardly argue against it. The same applies to the seller. Those who do not have one and problems occur, will probably be reluctant to admit that they may have made a mistake. However, not every single-family house must have controlled residential ventilation. In conclusion: Forum posts cannot replace professional advice and should therefore only be considered as a stimulus for further measures.
Best regards

Yes, many things speak in favor of it. But €uro first has to calculate whether it is worth it.

Economic efficiency

What are the rough(!!) benchmark values for the heating energy demand of a new 160 sqm house without a basement with 4 people, and how much electricity does a controlled residential ventilation system consume per year? And please don’t come again with unknown boundary conditions. Rough estimates are allowed if necessary... I would like a benchmark for what annual savings I could expect with heat recovery. 10€, 100€, 500€?...

Small side question: Can the controlled residential ventilation system actually be switched off in summer if you want/can sleep with the window open?

Hello,

according to our calculations and experience, the values for the heating energy demand, it would be better to say final energy demand, are as follows: For a well-insulated house, about 65 kWh/m²/a. The ventilation system saves around 12 to 18 kWh/m²/a with an efficiency of 80% (90% is already possible) at a self-consumption of about 4.5 kWh/m²/a. These values are based on our experience and are given here only as guidelines. For a specific construction project, the numbers are always calculated in advance, as the architecture and solar heat gains also play a major role.

Of course, the ventilation system can also be turned off if you want to sleep with open windows. From experience, however, this is rarely done anymore: - no more mosquitoes at night - no more noise in the apartment - it feels like fresh air all night long But basically, it is possible; if there is a party, of course all the windows are open, then the system should be switched off.

Of course, you can also turn off the ventilation system if you want to sleep with the window open. From experience, however, people hardly do this anymore: - no more mosquitoes at night - no more noise in the apartment - it’s like freshly aired, all night long But basically it’s possible; if there’s a party, all the windows are open anyway, then the system should be turned off.

Well, we currently live in the city and sleep with the window open. We are moving far out, building on a play street, so noise will probably be less of an issue. For example, I like it when the wind rustles through the trees or the birds are chirping The question is whether you should even run the ventilation then, which of course consumes electricity, when you CAN sleep with the window open and during the day the terrace door is constantly open anyway and it’s so warm that you don’t need to recover any heat (I have already turned off the heating in the poorly insulated pre-war apartment)

Sure, then turn off the ventilation. We also live at the end of a private road. It is truly a wonderful feeling with the window open. Then please remember to have a switch installed in the bedroom that allows you to turn off the entire system. Otherwise, you always have to go to the control unit, which is usually located in the reference room (usually the living room). Remote controls are available. This could also be controlled by a timer, so that the system runs during the day as well, which makes sense when you are at work. When it is very warm in summer, however, we keep the windows closed and cool our apartment, with an additional duct cooling our bedroom a little more. To support cooling the house, we turn off the system early, ventilate the entire house with cool air in the morning, and then close the windows again. The shutters go down automatically when there is direct sunlight.