HVAC Ductwork & Sheet Metal

Voomi Supply carries HVAC ductwork and sheet metal from Southwark Metal, Gray Metal South, McDaniel Metals, Quietflex and DuroDyne, including rectangular trunk and crossbroke duct, register boots, top takeoffs, reducers, transitions, end caps, insulated plenums and hangers. Ductwork and sheet metal fittings form the path that carries conditioned air from the equipment to each room and back to the unit, and every part has to match the duct run it connects to in size, shape, gauge and insulation. Every order ships with Voomi's 30-day return policy and free help matching a part to your system.

Customer Support Image
Need Support?

Call Jack and His Team

Duct Parts at a Glance

Part

What it does

What to match

Trunk and crossbroke duct

Rectangular duct for the main run

Cross-section size, length and gauge

Register boots

Connect ductwork to grilles at ceilings, walls or floors

The grille opening, duct size and orientation

Top takeoffs

Branch connection on top of a duct, sold here with a damper

Collar size and whether a damper is included

Reducers and transitions

Connect ducts of different sizes or shapes, such as square to round

Both end sizes and shapes

Plenums

A supply plenum takes conditioned air from the equipment and distributes it through the ductwork; a return plenum takes in room air and carries it back to the unit

Size, supply or return side, and R-value

End caps

Cap an open end or opening in a run

Diameter and gauge

Insulated sleeve duct

Insulated duct section sold by the length

Diameter, length and insulation

Hangers

Support duct runs

Duct size and mounting method

 

The product type filter on this page also lists duct access doors, duct angles, duct board and duct boots. For round and flexible runs, see our flex duct; for the grilles and registers that sit on a boot, see grilles, registers & diffusers.

Flexible vs. Rigid Duct

The right duct type depends on the installation. Flexible duct is faster to install and works well in tight spaces like attics and crawlspaces, while rigid sheet metal duct offers smoother airflow and greater durability on main trunk lines and long runs. See the comparison below.

Factor

Flexible Duct

Rigid Sheet Metal Duct

Installation

Faster, bends around obstacles

Requires precise fabrication and fitting

Airflow efficiency

More resistance when compressed, sagging or kinked

Smoother airflow, less resistance

Installed performance

Stretched fully, close to rigid duct; any slack, even 4 percent compression, causes a significant airflow loss

Holds its shape between supports

Typical use

Short runs, tight spaces (attics, crawlspaces)

Main trunk lines, long runs

 

A Texas A&M study of 6, 8 and 10 inch flex duct, summarized by Energy Vanguard, found flex and rigid metal duct perform nearly identically at 0 percent compression. At 4 percent compression, a 6 inch flex duct moved about 70 CFM against about 110 CFM for rigid metal at 0.1 in. w.c. Pull flex fully straight and support it so it does not sag.

How to Read Duct and Fitting Titles

Listings pack the size, gauge and finish into the title. Dimension order differs between fittings, so confirm which dimension is which on the product page.

Example title

What it tells you

Southwark TD601810 Trunk Duct 60 inch 18x10 Hot Dipped Galvanized

A 60 inch section with an 18x10 cross section, in hot dipped galvanized steel

Gray Metal South 10X4X6-110R 10 x 4 x 6 in. Straight Boot Galvanized Steel 30 ga

A straight register boot with three dimensions in inches, in 30 gauge galvanized steel

Southwark 17188168 18X8-16X8 Duct Reducer

A reducer from an 18x8 duct to a 16x8 duct

McDaniel Metals 161/2X141/2X36R8 3 Ft R8 Supply Plenum

A 3 ft plenum for the supply side with R8 insulation

Sheet Metal Gauge: What 28 and 30 ga Mean

A higher gauge number means thinner steel, and gauge numbers differ by material: 22 gauge is .0336 in for galvanized steel but .0253 in for non-ferrous metals such as aluminum. The product grid lists a 28 ga vent tee cap and 30 ga boots.

Gauge

Galvanized steel (in)

Galvanized steel (mm)

22

.0336

0.85

24

.0276

0.70

26

.0217

0.55

28

.0187

0.47

30

.0157

0.40

Sealing and Insulating Ductwork

Duct joints and seams leak unless they are sealed, and leaks waste conditioned air. According to the Building America Solution Center (PNNL), code-built homes typically leak about 10 percent, and a 1,000 CFM system with 10 percent leakage loses about 100 CFM, roughly 3,000 BTU per hour. The McDaniel plenums in the grid list R8 for supply and R6 for return.

Topic

Guidance

Sealing material

Use mastic or metal tape that meets UL 181. Standard cloth-backed duct tape can dry out and fail quickly.

Wide seams

Cover seams wider than 1/8 inch with fiberglass mesh tape before applying mastic.

Insulation in unconditioned space

At least R-8 on supply ducts and R-6 on return ducts under the 2009 IECC, Section 403.2. Check your local code.

Compression

Do not compress duct insulation, because compression reduces its rated R-value.

Browse more HVAC ducting & ventilation supplies, including blowers & inline duct fans, vent pipes & fittings and commercial ventilation.

Frequently Asked Questions

We carry rectangular trunk and crossbroke duct for main runs, register boots that connect ductwork to grilles at ceilings, walls and floors, top takeoffs with dampers, reducers and transitions for changing duct size or shape, end caps, insulated plenums for the supply and return sides, insulated sleeve duct and hangers. The product type filter also includes duct access doors, duct angles and duct board. Round and flexible runs have their own flex duct collection.

Yes. Reducers join ducts of different sizes, and transitions connect different shapes, such as square to round. Check both end sizes on the listing, because a reducer or transition has to match the duct on each side, and confirm the dimension order, since it differs between fittings. Seal every joint with mastic or UL 181 tape, and cover seams wider than 1/8 inch with fiberglass mesh tape first.

Several rigid parts here are galvanized steel, including hot dipped galvanized trunk duct, and fittings are listed in 28 and 30 gauge. For galvanized steel, 28 gauge is .0187 in thick and 30 gauge is .0157 in, and a higher gauge number means thinner steel. Plenums and sleeve duct are insulated, with the plenums listed in R6 and R8. Check each listing for material, gauge and insulation before you order.

The size and type of ductwork depend on your HVAC system’s specifications, including airflow requirements. You can refer to the product descriptions or contact our team for guidance.

Use duct mastic or metal tape that meets UL 181. Standard cloth-backed duct tape can dry out and fail quickly. For seams wider than 1/8 inch, cover them with fiberglass mesh tape before applying mastic. Sealing matters because leaks waste conditioned air: according to the Building America Solution Center (PNNL), code-built homes typically leak about 10 percent, and a 1,000 CFM system with 10 percent leakage loses about 100 CFM. The best time to test and fix leaks is before drywall goes up, while the ducts are still accessible.

For ducts in unconditioned space, the 2009 IECC calls for at least R-8 on supply ducts and R-6 on return ducts. Duct wrap is sold from about R-4 to R-8, so check the rating when you buy. Use a foil or plastic faced vapor barrier to prevent condensation, and do not compress the insulation, because compression reduces its rated R-value. Codes vary by location, so check yours.

Gauge varies by part. The product grid lists a 28 ga vent tee cap and 30 ga register boots. For galvanized steel, the thickness is .0157 in for 30 gauge, .0187 in for 28 gauge, .0217 in for 26 gauge, .0276 in for 24 gauge and .0336 in for 22 gauge. Gauge numbers differ by material, so 22 gauge is .0253 in for non-ferrous metals such as aluminum. Use the gauge on the listing rather than assuming it from the part type.

Stretched fully, flex duct performs close to rigid metal, but slack or compression cuts airflow. In a Texas A&M study summarized by Energy Vanguard, a 6 inch flex duct at 4 percent compression moved about 70 CFM against about 110 CFM for rigid metal at 0.1 in. w.c. The Air Diffusion Council manual suggests doubling the friction rate at 15 percent compression and quadrupling it at 30 percent, although the article argues those factors are optimistic. Flex is faster to install in tight spaces such as attics and crawlspaces, while rigid metal suits main trunk lines and long runs.

Yes, we offer shipping on all ductwork and sheet metal products. Shipping rates and options will be provided during checkout.