I am ready to install my flooring which is going to be stapled, 1/2 tongue and groove, plywood engineered acacia over 3/4 T/G OSB over a basement. I have been told that the white silicone underpayment is better that the 15# or 30# felt paper. Basement is still unfinished, has batted insulation between the floor joist. Any opinions ?

No comment here, I like paper that breathes a little.

Why is siliconized paper suppose to be better? Like Red Rosen... sounds funky, and like a sales gimmic.

Not sure what to make of it when it cost the same.

I've tried it and there appears to be no difference between it and felt .I actually prefer felt as it doesn't tear as easily.THe one underlayment that seems to actually block moisture better is aquabar.

Conditioned basement below with kraft backing insulation between floor joist, so moisture protection is not as important as reduction of friction between sub-floor and flooring. When you say felt paper do you mean rosin paper or tar roofing paper and why other than tears do you like it?

15 lb felt is the same as roofing paper. As for rosin paper, it is a cheaper alternative. I don't like the rosin very much because it tears too easily and if it gets wet , it wont be happy. Felt/roofing paper can handle getting wet to a certain degree.

Also, the felt does more to actually retard moisture transmissions.

I am at a loss to understand why anyone would want to block water vapor transmission in a wood substrate. Are you not just starting another issue with the wood subfloor getting to wet? My thinking is if you have a potential moisture issue underneath the subfloor then address the issue at hand, don't create a different one. Am I off base here?

I was told about something called the California Syndrome or something like that . Basically if you trap moisture between the underlayment and sub floor , you get into big trouble.

But as for your question, you aren't off base at all. I believe moisture transmission is necessary . Seems like the OP is debating which underlayment is the best . The teflon / silicon underlayment isn't particularly great so far.

Ahh..the "California Syndrome"....I was installing in CA when laminate first came to the states,(Pergo). I was certified by Perstorp, this was before the "2+1" underlayments, we used 6 mil visqueen under the foam. Pergo stated in their installation specs,( and other manufacturers followed), DO NOT install plastic "moisture vapor barrier", under the underlayment foam, when installing over wood subfloors. This will void warranties. Funny how now a days all the same manufacturers, that I know of, are supplying combo moisture vapor barrier and underlayment, for installation over wood subfloors.
One thing I'm not sure of though....At that time it was all glued up joints, now it's all "click". Not sure if that made a difference in their line of thinking.

I'm with SP though If there's moisture issues on a wood subfloor, take care of it. Why would you incapsulate it?

Something for you pros to ponder. You have to wonder. BR111 has been mentioning visqueen (6 mi poly) for years and still does...

Staple-Down Application – In the staple-down application, a
suitable moisture barrier (6 mil poly film) must be established
over plywood (or equivalent) with joints overlapped 18"
and taped.

But in their solid lines they say this...

A moisture barrier (6 mil polyethylene film
minimum) may be required in addition to the 15 lbs. asphalt
felt. Asphalt felt is not considered a moisture barrier.

And these specs have virtually been the same for years.

Ken, and when the subfloor rots out it is not their problem. Keeps the inspectors busy. But I bet a smart construction lawyer would make mincemeat outa them.

Very funny Howard.