ᐅ Operation / Efficiency of Decentralized Ventilation Systems

Hello!

We have been considering the question of centralized versus decentralized ventilation for our new build for quite some time now. There is a lot of information available, but I haven’t found anything conclusive regarding the actual functionality.

We are thinking about the decentralized units from Meltem, as these keep supply and exhaust air separate and provide continuous ventilation in both directions, rather than cycling back and forth. According to Meltem, one unit is suitable for 30 m² (320 ft²).

If I install the unit in a corner near the ceiling, it is hard for me to believe (or maybe just hard to understand technically) that effective air exchange would really take place in the opposite corner, which could be up to 6 m (20 ft) away. I can imagine that there is good air exchange within a 1-2 m (3-7 ft) radius around the unit. But that far? Also, there is no negative pressure pulling in air, since each unit in every room operates independently.

Not to mention the fact that warm air rises during summer and therefore doesn’t reach body height…

Can someone explain this to me from a physical perspective?

Thanks.

hausbauerin1

@hausbauerin1
We have the Lunos E2 with heat recovery.
With centralized ventilation systems, you generally get a much higher airflow rate for air exchange.
I can’t explain this “physically” since I haven’t studied it.

With the decentralized system, we achieve a certain baseline air exchange to prevent mold, drafts, and annoying fan or airflow noises.
If you want to actually feel the "fresh air," you shouldn’t use heat recovery or a system that never reverses the airflow direction.
Then you get a nice icy draft in winter. With heat recovery, it is cool but not freezing cold. So far, I haven’t noticed any condensation problems on the wall or floor under the unit.

Maintenance is much cheaper with the decentralized solution because it’s easy to access. That was my main consideration. It can also be significantly more affordable than a centralized ventilation system.

In a decentralized system, one fan usually exhausts air while the other draws air in. This is intended to create airflow throughout the entire floor, and this is how it is shown in the ventilation design. When the doors are closed and you feel around the bottom of the door with your hand, it actually works this way.

Decentralized systems are suitable for renovating existing buildings and, in my opinion, for new constructions only if you want to control ventilation in individual rooms (based on measured humidity or CO2 levels). In all other cases, I would plan a centralized system.

Thank you! Yes, if it works like that (balanced ventilation) I can imagine it too. However, with Meltem, each unit operates separately in each room, meaning air is supplied and exhausted simultaneously in the same device. I’m not sure if that still provides proper air exchange since it happens individually in every room. We prefer the Meltem units because supply and exhaust air run separately, which is usually not the case.