Thermaflex 54209000001 Insulated Flex Duct 9in X 25ft R-6

Product Description

The THERMAFLEX 54209000001 is a 9-inch diameter, 25-foot insulated flexible air duct rated R-6, designed for low to medium pressure HVAC distribution systems. The inner core is constructed from a polyester film laminated over a heavy, corrosion-resistant steel wire helix, providing structural support and flexibility under pressure. A thick blanket of fiberglass insulation surrounds the inner liner and is reinforced with a fiberglass scrim. The outer vapor barrier consists of a durable black polyethylene jacket that protects the insulation from moisture and mechanical damage. Licensed HVAC technicians install this product in residential and light commercial duct systems.

This flexible duct is suited for supply and return air distribution runs in attics, crawlspaces, and mechanical rooms where routing around obstructions is required. Its low-to-medium pressure rating makes it appropriate for standard forced-air systems using conventional air handlers and furnaces. The 9-inch diameter accommodates higher-volume branch runs and trunk-to-branch transitions. The 25-foot length reduces the number of joints needed on longer runs, supporting cleaner, lower-resistance duct layouts.

Key Features

• R-6 insulation value reduces heat gain and loss along distribution runs
• Corrosion-resistant steel wire helix inner core maintains shape under operating pressure
• Polyester film inner liner laminated to wire helix for durability and airflow integrity
• Fiberglass insulation blanket with fiberglass scrim reinforcement layer
• Durable black polyethylene outer jacket serves as vapor barrier
• Rated for low to medium pressure HVAC applications

Compatibility

Designed as an OEM-style replacement and new-installation flexible duct for residential and light commercial forced-air HVAC distribution systems operating at low to medium static pressure.

Installation Notes

Installation should be performed by a licensed HVAC technician in accordance with SMACNA guidelines and local mechanical codes. Disconnect and lock out power to the air handler or furnace before connecting or repositioning duct sections. Avoid sharp bends that reduce the interior diameter and increase static pressure drop. Secure all connections with approved clamps and mastic or UL-listed tape to maintain system integrity and prevent air leakage.