This is a very interesting thread.
Today my car was in for a check up of the Ventilated seats.
My complaint was that they were not cool enough.
When the outside air temp was colder (60's, some weeks ago) I would really feel quite quickly the cooling of the seats when you turn in on.
Now, when the temperture is moving towards the 80's, the seats seem to have more prolems cooling and that is why I brought the car in, thinking something was wrong.

My dealer confirmed that the AC is not involved in this system at all, and that (as also confirmed by a few on this board) the air is coming directly from the area below the seats.

This is a bit disappointing of course as this does explain why, when it get's warmer outside, the system is less effective as the air is warmer inside.
But isn't that why we bought this feature??

Very interesting what X5FX is saying as this seems to indicate that AC is somehow involved.

When the temperature goes above the 80, I simply have a hard time noticing the ventilation of the seats. And this seems to confirm that it is not controlled through the AC.

Maybe in markets where there is a higher average temperature, this does work through the AC? Would that be possible? Sounds strange, but might be the only explaination why people describe 2 different behaviors in this thread. One saying that the seats are really cold (also in warm air conditions) and the other, that it's not so noticable.

Curious about other thouhts.