Rigid fiber or fibrous board insulation consists of either fiberglass or mineral wool and is primarily used for insulating air ducts in homes. It is also used when there's a need for insulation that can withstand high temperatures.
Fiber or fibrous glass duct board insulation is manufactured from resin-bonded, inorganic glass fibers. These duct boards are available with coated or faced airstream surfaces. The outside surface of the boards typically incorporates a factory-applied reinforced aluminum air barrier and water vapor retarder. They come in a range of thicknesses from 1 inch to 2.5 inches. The boards can provide an R-value of about R-4.0 per inch of thickness.
The installation of fiber board insulation in air ducts usually requires an HVAC contractor.
HVAC contractors fabricate fiber board insulation into ducts either at their shops or at the job sites.
On exterior duct surfaces, they can install the insulation by impaling it on weld pins and securing with speed clips or washers. They can also use special weld pins with integral-cupped head washers. Unfaced boards can then be finished with reinforced insulating cement, canvas, or weatherproof mastic.
Faced boards can be installed in the same way. Joints between boards are sealed with pressure-sensitive tape or glass fabric and mastic.
Article source: The U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE). For the most up-to-date information please visit the EERE website.