Ventilation system central or decentralized

Hello everyone Maybe you can help me We have a small apartment 35 to 40 square meters 1 bathroom 1 master bedroom 1 living room and 1 storage room. In this apartment there is repeatedly a problem from about mid-October to about April, where an unpleasant musty basement smell arises The apartment is not used daily so the ventilation is also irregular There is no mold or similar Now I have already thought about a decentralized or centralized ventilation system I think with the centralized system all rooms are ventilated Would it solve the problem and are there ventilations available in the size that would fit so far I have only found larger systems or can they be adjusted down so that they would fit in size

1. Apartment = rented or owned
2. If owned, then the question is whether it is a condominium within a homeowners' association, or if you own the entire house
3. With the size of the apartment, a central system will be practically impossible to implement. You need a central device and the corresponding piping.
4. Decentralized = core drilling to the outside and installing the device or connecting it to the power supply (often even to the socket)
5. No daily use = no daily ventilation. Is it at least heated properly every day? Not that the musty smell has already gone towards mold

Would that solve the problem

At least provides permanently fresh air. The system does not help against musty odors if it is already tending towards mold (e.g., if it is heated too little).

are there ventilations that fit the size

Plenty of providers for decentralized systems.

The entire house is owned He is already heated there is no mold formation Piping for a central ventilation system would not be a problem due to the room layout My concern with a decentralized ventilation system is that not all rooms would be ventilated

It is already being heated

To what temperature in the rooms?

A piping system for a central ventilation system would be no problem due to the room layout

How do you want to do that? Lower the ceiling? Bulkheads over the rooms above or below the apartment? Supply air and exhaust air where? Where to place the central unit?

My concern with a decentralized ventilation system is that not all rooms would be ventilated

If you cannot install a device in every room and they are always closed first, then no.

Alternative: An exhaust fan and window rebate ventilator.

Central is – trust me – a stupid idea.

19 degrees is always in the rooms when no one is there
Attaching a cladding would not be a problem, it would only be 3 meters in the bedroom which is also to be painted soon, everything else can be installed in the basement room behind it
I have attached a sketch of what I had in mind
A decentralized ventilation system would, in my opinion, be more difficult since I would have to ventilate every room and would have to make 4 core drillings alone

If you cannot install a device in every room and they are always closed to you at first, then no.

I don't quite understand this. Attached is the sketch.