Thermaflex 53705000002 Flex Duct 5 in X 25 Ft R-4.2

Product Description

The THERMAFLEX 53705000002 is a thermally insulated, fully lined flexible air duct designed for low to medium pressure heating and cooling HVAC systems. Sold in a 25-foot length with a 5-inch diameter, it carries an R-4.2 insulation value and meets UL 181 Class 1 requirements. The silver outer jacket is standard for this duct type. It handles airflow in both supply and return applications, giving HVAC technicians a versatile solution where rigid fabricated ductwork is impractical, misalignment exists, or routing around structural obstacles is required.

This flexible air duct is suited for residential and light commercial HVAC installations. It works in new construction and retrofit projects equally well. Common uses include system extensions, zone changes, and connecting diffusers or registers to trunk lines where straight runs are not possible. Its flexibility allows installers to route conditioned air around framing, beams, and other obstructions without custom fabrication. It is installed by licensed HVAC technicians and sheet metal contractors working on forced-air heating and cooling systems.

Key Features

• UL 181 Class 1 rated flexible air duct for low to medium pressure systems
• R-4.2 thermal insulation value reduces heat gain and loss in the duct run
• 5-inch diameter by 25-foot length suits a wide range of branch duct applications
• Suitable for both supply and return air sections
• Fully lined interior supports airflow efficiency and limits condensation exposure
• Usable in new construction and retrofit or system extension work

Compatibility

Designed as an OEM-style replacement and general-purpose flexible duct for residential and light commercial forced-air HVAC systems requiring a 5-inch diameter, UL 181 Class 1 rated duct section.

Installation Notes

Installation should be performed by a licensed HVAC technician or qualified sheet metal contractor in accordance with SMACNA guidelines and local mechanical codes. Power down and lock out the air handling unit before connecting or disconnecting duct sections. Secure both ends with approved duct clamps and mastic or listed metal tape per UL 181B requirements — never use standard cloth duct tape. Avoid sharp bends that restrict airflow; maintain bend radii appropriate to the duct diameter.