Rental apartment - Uncertainty about installed decentralized ventilation systems

Hello everyone,

we are currently interested in a rental apartment in a new building. During the viewing, we discovered "slots" above the windows (see attached photos for interior and exterior views). According to the owner, these are decentralized ventilation systems. The heating system includes a heat pump in front of the house. So far, the owner has not provided more information, so I would appreciate an assessment here.

In my research, I only find decentralized ventilation systems that have a rectangular or round shape on both the inside and outside walls. In our case, however, only these "slots" are visible inside and nothing on the outside. It seems as if these are not decentralized ventilation systems, which would mean that the owner himself does not exactly know what is installed in his new building. That naturally causes uncertainty.

I know - a single photo is not much, but unfortunately, we do not have more at the moment. Perhaps someone in this forum can still assess what kind of ventilation system (or whatever it is) this might be? For example, we also wonder whether a summer bypass is integrated and whether we could control the ventilation systems ourselves to prevent hot air from being blown into the apartment in summer.

We look forward to any input. Thanks in advance and best regards!

For me, this is a window ventilator integrated into the external shutter box. Similar to a window rebate ventilator. Somewhere there will still be 1-2 exhaust fans in the apartment. The cheapest solution to achieve a minimum air exchange without user intervention.

Hello hanse987, thank you for your feedback. Would you then also assume that no heat recovery is integrated and the air flow is not controllable?

Hello hanse987, thank you for your feedback. Would you then also assume that no heat recovery is integrated and that the airflow is not controllable?

He wrote it like that, yes. I see it the same way. Ventilation is ensured, but no additional technical comfort. However, I do not see that as necessary in a rental apartment or investment property either. Tenants are usually not happy to pay for this investment. You will not notice anything negative from the "ventilation," just like with window rebate ventilation.

I don't quite see it that way. A controlled residential ventilation system with heat recovery significantly contributes to energy saving. A window frame ventilator combined with exhaust fans means cold air in and warm air out.

The house is a low-energy house with triple-glazed windows. Installing ventilation there that lets cold air into the apartment (uncontrolled) in winter somehow doesn't fit at all. We will try to get more information from the owner.

Thank you very much for the answers :)