ᐅ Slot vents & Placement of Mechanical Ventilation Systems

Hello,

I couldn’t find any information on this, so I have the following question:

I am currently renovating an old building and would like to install a Bora cooktop with a downdraft extractor (recirculation mode) in the open-plan kitchen. In addition, I will install a decentralized mechanical ventilation system with heat recovery and two fans. One of these fans is planned to be positioned near the kitchen’s exterior wall, close to the cooktop area.

Do you think the airflow from the ventilation system could affect the performance of the downdraft extractor? The extractor is installed near ceiling height, but it can move a significant volume of air (up to 50 m³/h (30 cfm); standard settings are usually 15 or 30 m³/h (9 or 18 cfm), depending on the setting).

Has anyone had experience with this? Are there recommended minimum distances between such ventilation fans and downdraft extractors, or is this generally not an issue? I would appreciate any feedback.

Best regards,
Julian

Should the downdraft extractor be installed as an exhaust system?

Recirculation is mentioned in the text....

I cannot imagine that the airflow has any effect on the downdraft extractor. There is no "deep suction effect." You can observe this with overhead hoods. Only tornado-style hoods (e.g., Berbel) can somewhat direct the airflow. Otherwise, only the self-rising fumes are extracted. Moreover, decentralized mechanical ventilation with heat recovery (MVHR) systems operate in push/pull mode (timed intake/exhaust) to prevent the room from being "emptied" of air.

However, before installing a decentralized fan with heat recovery, you should listen to one in a live test. You might reconsider and opt for a centralized mechanical ventilation system instead. They are not completely silent, and anyone claiming they are inaudible is probably not using their hearing aids. The cost is higher for a centralized system, yes. But with mechanical ventilation with heat recovery, a large portion (up to 100%) of the work can be done by yourself. It’s not rocket science. 😉

@i_b_n_a_n ... Reading clearly educates 😉 .. I also see little impact there. It's important to plan the exhaust air flow in the base properly to avoid it blowing directly onto your feet. But I also see rather minimal effects. And when you consider how much air a range hood can move, then the 50m³/h (59 cubic feet per hour) of controlled residential ventilation is very little.

Yes, it will be a recirculation version of the downdraft extractor.
I also believe that, in relative terms, it doesn’t make much difference, but I wanted to ask just to be sure.

I read somewhere that downdraft extractors are quite sensitive to crossflows.

I asked my energy consultant about it again, but he didn’t really provide a clear answer. He rather suggested installing the ventilation system as far away as possible from the greasy kitchen vapors, since these can "clog up the ventilation over time," even if a range hood is installed.