Rmax R-Matte® Plus-3 is an energy-efficient thermal insulation board composed of a closed-cell polyisocyanurate (polyiso) foam core bonded to reinforced aluminum facers on each side. While one side of the board has a reflective surface, the other side has been coated to have a nonreflective white matte surface. Boards can be installed with either the silver or white side out. For additional radiant barrier properties, install silver side against air space if one exists.