Quietflex 18KM Flex Duct 18 in R-4.2 Foil Jacket 25 Ft

Product Description

The QUIETFLEX 18KM is a flexible, insulated air distribution duct built for large-diameter HVAC supply and return applications. The 18-inch diameter core is wrapped in an insulated blanket rated at R-4.2 and enclosed in a foil outer jacket that resists vapor infiltration and supports long service life. Each piece ships in a 25-foot length, reducing splice points on extended runs. This product is installed by licensed HVAC technicians and sheet metal contractors in both commercial and residential air distribution systems where high air volume and routing flexibility are priorities.

The 18KM is suited for trunk extensions, high-volume branch runs, and large return plenums where rigid ductwork is impractical. The 18-inch diameter handles substantial airflow, making it a common choice for commercial light-duty systems and oversized residential applications. The flexible construction allows the duct to route around structural obstructions without custom fabrication, reducing labor time on complex installs. The foil jacket provides a clean, reflective outer surface compatible with standard duct supports and hangers.

Key Features

• 18-inch diameter core sized for high-volume supply and return runs
• R-4.2 insulation rating reduces thermal loss along distribution runs
• Foil outer jacket provides vapor resistance and durability
• 25-foot length minimizes connection points on long runs
• Flexible construction routes around framing and structural obstacles without custom fabrication

Compatibility

Designed as an OEM-style replacement and new-installation flexible duct for large-diameter HVAC air distribution systems requiring an 18-inch round duct with R-4.2 insulation and a foil jacket.

Installation Notes

Installation should be performed by a licensed HVAC technician in accordance with SMACNA flexible duct installation standards and applicable local mechanical codes. Power down the air handling unit and confirm the system is depressurized before making duct connections. Secure the inner liner, insulation, and outer jacket separately at each fitting using approved draw bands and mastic or UL 181-listed tape. Avoid sharp bends that compress the inner liner, as this reduces effective airflow area and system performance.

Technical Specifications

• Diameter: 18 inches
• Insulation Rating: R-4.2
• Jacket Type: Foil
• Length: 25 feet

Standard Information

• Brand: QUIETFLEX
• Manufacturer Part Number: 18KM