ᐅ Is a Mechanical Ventilation System Only Practical for a Three-Bedroom Home?

Hello,
we are currently planning a new single-family house (9m x 9m (29.5ft x 29.5ft), 2 floors plus basement). We were offered compliance with the Energy Saving Ordinance 2009 or, alternatively, KfW 70 standard for an additional 13,000 EUR.
In addition, a residential ventilation system was offered for the 3 bedrooms on the first floor with a surcharge of 3,850 EUR (Selfio EuroAir 180m³/h (106 cfm)).

So far, I have only read about ventilation systems for the entire house. How sensible is it to install the ventilation system only in the bedrooms?
Are there any disadvantages if the ventilation system is not connected to the whole house?
If building according to KfW 70, shouldn’t the whole house have a ventilation system regarding issues like mold growth?

Best regards
eineuro

Well, since it is a central system, you can of course install the supply air vents in the bedrooms and the exhaust air vents in the bathrooms/kitchen... that way you have a central system for the entire house, not just the bedrooms. However, I would recommend the Euroair 250; the extra cost is minimal, but it provides significantly higher airflow.

And while you’re at it, you should also install supply air vents in the living areas… they’re not very expensive.

However, careful planning of the whole system is essential… just installing it without proper planning will result in poor performance.

When I asked about a ventilation system for the entire house, I was told that they do not offer that...
I suspect they don’t really know because the system would actually allow for that.

The main benefits of such a system are usually only achieved if it is set up for the whole house, right?

Does it make sense to potentially outsource this kind of system?

Yes, it actually makes a lot of sense, because then you can find someone who is experienced and does this kind of work every day...