ToughGard™ rigid liner board is a thermal and acoustical board that features a tougher, smoother, more damage-resistant composite airstream surface that ensures a long-lasting, efficient duct system, says the company. Composed of rotary-glass fibers bonded together with a thermosetting resin, the board is part of the company’s family of IAQ-sensitive hvac insulation products, the company says. The product is used primarily as an acoustical liner in sheet metal ducts, plenums, and equipment housings that supply conditioned air.