I have red rosin under one of the other floors in my house, and I don't think it does anything for moisture. Judging from what I've read other places, it's useless for a moisture retardant.

15 lb asphalt felt... I'd do it, but I'll be able to smell it for weeks. Plus, I don't really want to deal with the black marks on everything.

Can I use 6mil poly? I would assume no, since the wood needs to breath, right?

So my last option is Aquabar. Is this my best option? Where can I find this stuff? Home Despot doesn't have it, that I could see anyway. Would a hardwood flooring warehouse supply place have it?

Aquabar !!!!

I noticed that the people that make Aquabar also make something called HWD-15, specifically for hardwood floors. Has anyone used this stuff?

Where can I buy these products? I can't find them anywhere here in Minneapolis.