Doesn't your instruction manual tell you how much clearance to have??? I bought a De Dietrich, which is just the French version of the Diva, and it had very specific instructions on clearances and installation. You may also wish to visit the Diva web site and look at their installation instructions.

We have a Brandt, which is a low-end Diva. We have a drawer beneath our unit.

As per our install recommendations, the drawer is slightly shorter than the others in the stack to allow for ventilation.

This said, follow Diva's clearance recommendations.

Try the Diva website, and choose Residential under Products on the menu, then choose your model. There are .pdf's of both the brochure and the specs.

From the specs for the DDP-4:

Clearance
You should keep:
- In the back of your unit - between the unit and any
vertical surface: minimum clearance of 10 mm (3/8");
- If a downdraft ventilation system is used - between the
unit and the downdraft snorkel: minimum clearance of
6 mm (1/4");
- Above the unit to any combustible surface - e.g. cabinet
above the unit: minimum clearance of 750 mm (30");
- Below the unit - between the bottom of the unit and any
horizontal partition inside your cabinet: minimum clearance
of 50 mm (2").

I have the Diva DDP-40 and had to convert the top drawer underneath it to a false-front drawer in order to provide sufficient ventilation space.