Quietflex 5KMR8 Flexible Air Duct 5 Inch R-8 25 Foot

Product Description

The QUIETFLEX 5KMR8 is a flexible HVAC air distribution duct built for small-diameter branch runs in unconditioned spaces such as attics, crawlspaces, and mechanical rooms. It ships in a 25-foot length with a 5-inch inside diameter, an R-8 insulation rating, and a foil outer jacket. The high insulation value keeps conditioned air from absorbing heat as it travels through unconditioned cavities, reducing thermal losses between the air handler and the diffuser. Licensed HVAC technicians install this duct as part of low-pressure residential and light-commercial distribution systems where flexible routing around framing and obstructions is required.

This flex duct is suited for branch run connections to diffusers, registers, and terminal units in residential and light-commercial forced-air systems. The 5-inch diameter fits standard round collars on plenum takeoffs, flex connectors, and sheet-metal transitions. The R-8 insulation value meets the higher-efficiency requirements now common in IECC-compliant installations, making this duct appropriate for attic runs where thermal performance directly affects system efficiency and delivered capacity.

Key Features

• R-8 insulation rating reduces heat gain and loss in unconditioned spaces
• 5-inch inside diameter fits standard round collars and plenum takeoffs
• Foil outer jacket provides a durable, vapor-retarding exterior layer
• 25-foot length reduces the number of field splices on longer branch runs
• Flexible construction allows routing around framing, joists, and obstructions

Compatibility

Designed as an OEM-style replacement and new-installation flex duct for residential and light-commercial forced-air HVAC distribution systems requiring a 5-inch round flexible duct with R-8 insulation.

Installation Notes

Installation should be performed by a licensed HVAC technician in accordance with SMACNA flexible duct installation guidelines and local mechanical codes. Power down and lock out the air-handling unit before connecting or repositioning duct sections. Secure each end with an approved metal clamp and UL 181B-listed tape or mastic — never use standard cloth duct tape on pressure duct connections. Avoid sharp bends and compression, as both reduce effective airflow and increase static pressure drop.

Technical Specifications

• Inside Diameter: 5 inches
• Insulation R-Value: R-8
• Outer Jacket: Foil
• Length: 25 feet

Standard Information

• Brand: QUIETFLEX
• Manufacturer Part Number: 5KMR8