How To Install A Floor In A Aluminum Boat In-floor Radiant Heat- What Is This Black Paper? Can I Still Install?

In-floor radiant heat- what is this black paper? Can I still install? - how to install a floor in a aluminum boat

I am in the design of a radiant heat source ground while rebuilding my floor joists of the basement is exposed, and would PEX and to be able to absorb heat transfer plates of aluminum in the soil. However, as I explained in the basement there is a black paper between the subfloor and wood flooring on the first floor. The document looks like black paper. I am afraid that an asphalt felt paper. If so, should drop the whole project to be? How do I know?

PS-I also see many people stuck with nails through the bottom of the I cut it?

Thank you!