InsulBase HD is a rigid-roof insulation cover board composed of a high-density closed-cell polyisocyanurate foam core bonded on each side to glass-reinforced felt (GRF). Suitable for both re-roofing and new construction applications, InsulBase HD is specifically designed for use as a cover board in mechanically-attached single-ply systems only. InsulBaseHD delivers an R-value of 2.5 and a compressive strength of 80 psi.