Under floor heat

My house has under floor heat system it has water lines running on the joist 1" below the floor. They are presently just covered with pink bath insulation R12. With no air gap.

I was woundering if I should put reflective Vapour Barrier with the reflexive side facing toward the floor just above the water line and staple it on the side of the floor joice, then put the R12 insulation against the back side of the Roll Reflective Vapour Barrier. This would create the air gap.

Or should I use AtticFoil Radiant Barrier Foil.

Thanks!