Our rFOIL 1620 Ultra CBF series is made extra tough for over slabs (as a concrete underlayment) and under flooring. It provides exceptional thermal value and a strong, permanent vapor and radon barrier. Because radiant heat loss is reduced, floors are warmer and more comfortable. Ultra CBF consists of a single layer reflective sheet laminated between two layers of ultra-strong polyethylene bubble. At a compression strength of 140 psi Ultra CBF is our recommended product to install beneath a concrete slab or as part of an in-floor radiant heating system to make it more efficient. Ultra CBF offers superior puncture resistance and tear strength and withstands job site traffic. Ultra CBF conforms around plumbing, wiring and other obstructions and easily installs over any grade. Compared to rigid PE board insulation, Ultra CBF is easier to handle, cut, and install AND has nearly six times the compression strength.