Plastic under chipboard flooring?

[ats]

My house manufacturer has delivered building plastic for walls but not for the floor (upon carefully reading the quote, building plastic is also missing in the floor description).

Now the frame is completed and I am busy with everything else...

My construction manager thinks that building plastic under the floor chipboard is important. I got curious. It should function as a vapor barrier.

But... on top of the floor, I'll have 15 mm tongue-and-groove pine. So the indoor air has to travel through 15+22=37 mm of solid wood to get beneath the chipboard. Shouldn't these 37 mm constitute a fairly strong vapor barrier? (and it's not a wet room above).

I'm wondering if building plastic in the floor is: essential, good to have, possibly good to have, or completely unnecessary.

My construction is 220 mm of mineral wool in a wooden framework on top of a well-insulated crawl space.

Grateful for good arguments either way.

 

[para]

I place the plastic over the chipboard.
I want to glue the chipboard to the joists and then the plastic doesn't work there.

 

[BigGitt]

The plastic SHOULD be placed over the floor chipboard.

 

[ats]

Thank you for the answers, it will be on top of the floor chipboard.

I had already started screwing and gluing the floor chipboard when I heard this,

Nice.