Flexible ducts insulated with fibrous glass are an efficient, economical way to install connections between trunk ducts and room diffusers or registers. A spiral wire-reinforced inner air conduit is wrapped with resilient fibrous glass and jacketed with a flexible vapor retarder of reinforced foil or plastic film. These flexible products can conform to bends when connecting trunk ducts to diffusers, or when routing ductwork through obstructed areas. (NAIMA members do not manufacture flexible ducts, but do supply the flexible duct industry with fibrous glass insulation.)

Fibrous glass insulated flexible ducts can be used in applications where internal air temperatures do not exceed 250°F (121°C).

Fibrous glass insulated flexible ducts systems are manufactured to comply with Air Diffusion Council Test Code FD-72-R1. They also meet requirements of UL181, and comply with all widely used model building codes.