While Modin Rigid Vinyl Plank is waterproof, it is not a moisture barrier. It's a good idea to install a moisture barrier in the crawl space and between Modin Rigid Vinyl Plank and your concrete subfloor.
Make sure concrete is cured and tested for moisture and that a moisture barrier is installed in the crawl space and/or between Modin Rigid Vinyl Plank and the concrete subfloor.
Moisture won’t damage Modin Rigid Vinyl Plank, but it can get in the walls and structure of the home. Mold could develop, and that can cause certain medical reactions in pets and people. As such installing a moisture barrier is a smart idea, even if the Modin Rigid won't damage.