HVAC Flex Duct

Voomi Supply carries insulated and non-insulated flex duct from Quietflex, Atco, J P Lamborn, and Thermaflex, in diameters from 6 to 20 inches and R-values from R4.2 up to R8. Flex duct is a flexible, corrugated air duct used in place of rigid sheet metal for runs that need to bend around joists, beams, and tight framing, and most residential and light-commercial supply and return runs use an insulated version to control condensation and heat loss. Every order ships with Voomi's 30-day return policy and free help matching a duct to your run.

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Insulated vs. Non-Insulated Flex Duct

Insulated flex duct wraps the inner corrugated core in fiberglass insulation under a foil-scrim-kraft (FSK) vapor-retarder jacket; non-insulated duct is just the bare inner liner. The R-value tells you how much thermal resistance that insulation layer provides:

R-Value

Best For

Example SKUs

Non-insulated

Fully conditioned spaces with minimal temperature difference between the duct and surrounding air

Thermaflex KM series

R4.2

Interior runs in conditioned spaces where duct and room temperatures stay close together

J P Lamborn MHP25B

R6

Attics and crawlspaces in moderate climates, balancing insulation against cost and weight

J P Lamborn MHP25R8B*

R8

Unconditioned attics, long runs, or colder climates where minimizing heat loss and condensation matters most

Quietflex 1485, 785C

 

*Some J P Lamborn part numbers include the R-value in the SKU itself; check the listing to confirm before ordering.

Sizes We Carry

Common diameters in this collection include:

6"

7"

8"

9"

10"

12"

14"

16"

18"

20"

 

Match the diameter to your existing duct or takeoff collar, not to the register size, since a run often steps down in diameter between the trunk and the final register.

UL 181 Class 1 Fire & Smoke Rating

UL 181 is the safety standard flex duct is tested against for fire and smoke performance, and a Class 1 listing means the duct's outer jacket meets the flame-spread and smoke-developed limits most building codes require for HVAC ductwork. Products in this collection, including the Atco UPC 036 line, are UL 181 Class 1 rated. If your local code or inspector requires a Class 1 listing, confirm it's called out on the product's UL label before installing.

Duct Insulation Accessories

Alongside full flex duct runs, this collection carries the insulation products used to finish a duct system: Owens duct wrap for insulating rigid metal duct runs, Quietflex insulation sleeves for wrapping duct connections and transitions, and Thermo Manufacturing fire-resistant duct panning sheet for sealing subfloor return air plenums. These are sold separately from flex duct itself and serve rigid ductwork and platform returns rather than the flexible runs above. For rigid sheet metal duct and fittings, see our Sheet Metal & HVAC Ductwork collection.

Frequently Asked Questions

Flex duct is a flexible tubing used to transport air in HVAC systems. It’s easy to install, lightweight, and ideal for tight spaces where rigid ductwork would be difficult to install.

We carry flex duct from 6 to 20 inches in diameter, in non-insulated and R4.2, R6, and R8 insulated versions, from brands including Quietflex, Atco, J P Lamborn, and Thermaflex. Check each listing for the exact diameter, R-value, and length.

Yes, our flex duct is made from high-quality materials, including reinforced insulation and durable outer jackets, designed to withstand various environmental conditions.

Yes, flex duct is versatile and can be used in both residential and commercial HVAC systems for air distribution and ventilation.

Flex duct is relatively easy to install. Simply connect the ends of the duct to the appropriate fittings or registers. For proper installation, follow the manufacturer's guidelines or consult with an HVAC professional.

Choose insulated duct for any run passing through an unconditioned space, like an attic or crawlspace, to control heat loss and prevent condensation. Non-insulated duct is generally only appropriate for runs that stay fully within conditioned space.

Yes. Multi-unit orders qualify for quantity-based pricing, and contractors and service companies can set up a trade account for faster reordering. Contact our support team to get pricing on a bulk order or set up an account.