JD wrote:
I am not sure what you mean.
It is my current home and we are upgrading from carpet to hardwood. We will
be in the house another 10-15 years. One of the installers uses a product
called AquaBar, which appears to be a sandwich of paper with a tar like
substance in the middle. The argument he makes is that poly will leave
holes but this aquabar paper seals around the staples. It makes sense to me
on the surface, but I am still looking for advice.

AquaBar seems to be a laminated kraft paper/building felt (tar paper)
product.
http://www.fortifiber.com/floor_prot...ison_chart.htm

Regular 15# asphalt-impregnated building felt is what I put under
hardwood floors. Some people use red rosin paper, but I like the vapor
barrier qualities of the felt. AquaBar is essentially more expensive
building felt. I'd choose that over polyethylene. I'd choose building
felt over AquaBar and ask for a discount.

Frankly, the sealing around the staples is gilding the lily. The
amount of moisture that would be introduced thorugh the staple holes is
insignificant. If moisture through the staple holes is a problem, then
you don't solve it at the floor underlayment level, you solve it down
in the crawlspace with a barrier placed on the soil/cement and/or
ventilating the crawlspace. Otherwise you're essentially saying, "I
don't mind if the floor joists and subfloor rot, as long as my hardwood
floor looks good." That's crazy talk!

R