Central ventilation system control completely through the attic?

Or suspend the ceiling and put the pipes in there. So within the thermal envelope. The additional 8cm can be planned by raising the suspended ceiling if otherwise the clear room height becomes too low.

All correct, we are currently planning in the existing building and I don’t have enough space in the suspended ceiling on the upper floor. That means on the upper floor I have to come down from the attic. And at the moment the attic is a cold roof, we could change it to a warm roof as part of the roof renovation, but of course that is significantly more expensive than just wrapping a few pipes a bit.

Our pipes are installed that way, but our roof is insulated. However, our attic is also not heated. But perfect for storage.