Klaus Kragelund wrote:

Thankyou for the very good points

You are welcome.

I should have said I'm situated in Denmark (just north of Germany :-)

Danish people might permit a tiny amount of dust on the upper foil.
Then again, they build airtight houses, so excess moisture could be
a problem in summertime.

Currently no mostiture film is used. I want to add a wooden floor with
a carpet on top of this.

You may not need the wood.

The basement is dry, but my intention was to add ventilation holes in
the wooden floor and use no platic film to allow the construction to
"breathe". But adding plastic film might be a good idea since this also
limits heat flow caused by travelling moisture.

Upwards heatflow could be nice in wintertime.

Nick