Condominium with KFW70, unsure regarding ventilation

Evening,

I have been looking for a ground floor condominium for some time now, 2-3 rooms and 75 m² of living space.
Tomorrow morning I have a viewing appointment in a new building, completion is planned for June 2014.

Since this would be my first property purchase, I am an absolute beginner in the field of heating, ventilation, and controlled residential ventilation :)
I have tried to educate myself all weekend. The topic of ventilation technology keeps coming up again and again.

According to the energy certificate of the condo I want to view tomorrow, window ventilation is sufficient. Due to various posts here in the forum, I am now very uncertain.

I have a faint suspicion that the realtor will try to make the apartment attractive to me even without ventilation.

I think that at the current construction status (roof including tiles are already on) it will no longer be possible to install a central exhaust system. What do you think about a decentralized solution, for example Viessmann Vitovent 200-d?

The room layout is as follows: living kitchen 29m², bedroom 14m², office 11m², bathroom 5m², guest bathroom 2.5m², hallway 7m²

I would be very grateful for any help, after all, my first property purchase should not become a nightmare

Hello,

...According to the energy certificate of the condominium, which I want to visit tomorrow, window ventilation is sufficient. Due to various posts here in the forum, I am now very uncertain...

The energy certificate has nothing to do with DIN 1946-6. According to its definition, window ventilation is a recognized method of ventilation.
Much has already been written here about the pros and cons of controlled residential ventilation. Everyone has to weigh this up for themselves.

...I have a quiet premonition that the broker will try to make the apartment appealing to me even without ventilation tomorrow...

This does not necessarily have to be a disadvantage in individual cases!
As always, the crucial factors are the boundary conditions. For windowless rooms, DIN 18017-3 or the respective state building regulations apply.
If controlled residential ventilation, then with heat recovery!

Best regards.