Does the Quiet Walk underlayment plastic/vapor barrier face up or down when installing?

The plastic side faces up and the fiber faces down. Two benefits are provided:

Moisture Protection

The fibers can actually allow the vapors to evaporate through the gutter system of the underlayment. The fibers are treated with a safe anti-microbial to inhibit mold and mildew.

Protection from Leaks

Spills, leaky plumbing, faulty ice-makers can cause floor damage. QuietWalk underlayment fibers can absorb up to 5 times it’s own weight, drawing harmful moisture in while protecting the overlying floor.