Flexduct 665C Flex Air Duct R-8 6 in X 25 Ft Fiberglass

Product Description

The FLEXDUCT 665C is a UV-inhibited, fiberglass-insulated flexible air duct rated at R-8 thermal performance. Built for residential and light commercial HVAC systems, this duct ships in a 25-foot bag and measures 6 inches in diameter. The black outer jacket resists UV degradation, making it suitable for attic installations where sun exposure through roof gaps or unsealed penetrations is a concern. Licensed HVAC technicians and sheet metal contractors install this product as part of forced-air distribution systems to connect air handlers, plenums, and registers with flexible routing that accommodates structural obstructions.

The 665C is designed for use in residential and light commercial forced-air heating and cooling systems. The 6-inch diameter suits a wide range of branch-run applications, including supply runs from trunk lines to ceiling and floor registers. The R-8 insulation value exceeds minimum code thresholds in most jurisdictions for unconditioned-space duct installations, including attics and crawlspaces. The fiberglass inner liner keeps airflow smooth while the flexible core allows the duct to bend around framing members and other obstructions without collapsing the inner liner when properly installed and supported.

Key Features

• R-8 fiberglass insulation provides high thermal resistance for unconditioned-space runs
• 6-inch diameter inner core suits standard branch-run supply applications
• 25-foot length per bag reduces the need for mid-run splices on typical residential runs
• UV-inhibited black outer jacket withstands attic sun exposure
• Flexible construction routes around framing and structural obstacles

Compatibility

Designed as an OEM-style flexible duct replacement or new-installation duct for residential and light commercial forced-air HVAC distribution systems using 6-inch round branch fittings and collars.

Installation Notes

Installation should be performed by a licensed HVAC technician in accordance with ACCA Manual D duct design guidelines and applicable local mechanical codes. Power down and lock out the air handler before connecting or disconnecting duct sections. Support the flex duct at manufacturer-recommended intervals to prevent sagging, which can restrict airflow and reduce system efficiency. Avoid sharp bends that compress the inner liner, as excessive bends increase static pressure and reduce airflow to the served register.

Technical Specifications

• Inner Diameter: 6 inches
• Length: 25 feet
• Insulation Type: Fiberglass
• Insulation R-Value: R-8
• Outer Jacket: UV-inhibited black

Standard Information

• Brand: FLEXDUCT
• Manufacturer Part Number: 665C