Flexduct 520C Flex Air Duct R-4.2 5 in X 25 Ft Fiberglass

Product Description

The FLEXDUCT 520C is a UV-inhibited fiberglass flexible air duct rated at R-4.2 insulation value, measuring 5 inches in diameter and 25 feet in length. It is designed for use in residential and light commercial HVAC distribution systems where flexible duct runs connect supply plenums or branch takeoffs to diffusers and registers. The black outer jacket provides UV resistance, making it suitable for installations with incidental light exposure such as attic and crawlspace applications. Licensed HVAC technicians are the primary installers. The R-4.2 insulation rating meets common energy code minimums for conditioned air distribution in many climate zones.

This flexible duct is used in forced-air heating and cooling systems, typically installed in attic spaces, suspended ceiling plenums, and crawlspaces. It is well suited for connecting metal trunk lines to ceiling or floor diffusers in residential construction and light commercial retrofit work. The 25-foot bag length accommodates standard run lengths without requiring splices on most residential jobs, reducing potential air leakage points in the distribution system.

Key Features

• R-4.2 insulation value meets energy code requirements for flex duct in many jurisdictions
• UV-inhibited outer jacket rated for attic and crawlspace installations with incidental light exposure
• 5-inch diameter fits standard branch takeoff collars and boot connections
• 25-foot length reduces the need for mid-run splices in typical residential duct runs
• Fiberglass inner liner construction for low air resistance and durability
• Black outer jacket for compatibility with exposed or semi-exposed install environments

Compatibility

Designed as an OEM-style replacement and new-construction flexible duct for residential and light commercial forced-air HVAC distribution systems using 5-inch branch connections.

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. Fully extend the duct before securing to minimize airflow restriction caused by compression or excessive bends. Seal all connections at takeoff collars and boot fittings with listed duct mastic or UL 181B-listed tape before insulating over joints. Support the duct at intervals specified by local code, typically no more than 4 feet, to prevent sagging that reduces system performance.

Technical Specifications

• Diameter: 5 inches
• Length: 25 feet
• Insulation R-Value: R-4.2
• Jacket Material: UV-inhibited fiberglass
• Jacket Color: Black
• Package Dimensions (L x W x H): 7 inches

Standard Information

• Brand: FLEXDUCT
• Manufacturer Part Number: 520C