We have a basement slab that has 2″ of XPS under it and on the sides, and a Stego-wrap vapor barrier between the insulation and the concrete. It has had 13 years for the concrete to dry out since construction. For the subfloor, I’m wondering if Delta-FL under OSB or plywood would be a bad idea, as the concrete couldn’t dry in either direction if it were to get wet. Would DriCor with its ventilated installation (or the Delta-FL, leaving a ventilation gap instead of sealing the edges as instructed) be a better idea? I would assume that with the insulation underneath, the concrete would be close to the interior temperature and no condensation would occur. I would like to use engineered wood flooring as the finish material. I know that there was an article on this very topic, but it was assuming the slab that didn’t have a vapor barrier and insulation underneath.