When installing wood laminate flooring over plywood subfloor over crawl space, ismoisture barrier needed?

Yes, I found one always needs a moisture barrier that they sell along with the laminate flooring by the square foot. It looks like bubbled plastic wrap.

Hi bigfoot. You must have got a salesperson who doesn't want to sell you the moon. Just make sure you get ALL the proper tools to install the lam. Flooring, I didn't and have a real mess and a lot of gaps. Every piece has to be absolutely tight to the next. And... buy the best grade possible. AND when washing no water, just a damp mop, otherwise you will get bubbles at the joins. Trust me.

If your crawl space is encapsulated and conditioned (highly recommended) , you will not need a moisture barrier.
The encapsulation will keep moisture from the ground and outside air out of the crawl space.
A conditioned crawl space will not grow mold, damage your floor joists, sub floors, insulation or the laminate.

It is a relatively inexpensive improvement, that will also save you some money on energy bills. According to studies by Advanced Energy and Habitat for Humanity, homes with conditioned crawl spaces are about 18% more energy efficient than traditional vented ones.

Source:

Crawl Space Guide: Create Home Energy Efficiency & a Healthy Home (http://www.dirt-crawl-spaces.com)

Advanced Energy (http://www.crawlspaces.org)