Fibrous glass insulation boards may be applied to the exterior of sheet metal ducts, housings, and plenums. These semi-rigid to rigid boards are also suitable for insulating chillers and other cold or hot equipment, and can be used in applications operating within the temperature range of 0˚F (-18˚C) to 450˚F (232˚C). They are available in thicknesses from 1 in. (25 mm) to 4 in. (102 mm) in 1/2 in. (13 mm) increments.