Flex Duct vs. Rigid Duct: Pros, Cons, and Costs

You have ductwork to thank for distributing air throughout your home and keeping a comfortable temperature year-round. If you're considering upgrading or installing your home's HVAC system, you need to choose between different types of ductwork: flex or rigid. Learn how these two duct types compare so you can choose the one that works for you.

Flex Duct vs. Rigid: Key Differences

Flexible ductwork can be made from silicone, rubber, plastic, or plastic-coated fabric, while rigid ducts are made from aluminum or steel. While flexible ducts can change size to fit a particular area, rigid ducts are always the same size and may be shaped like tubes or rectangles.

Other key differences between flex and rigid ducts include their price, ease of installation, and longevity.

What Are Flex Ducts?​

Flex ducts are shaped like a tubes and consist of a wire coil covered with plastic, silicone, or fabric. They can be easily bent and twisted.

Best for: 

• Homes with lots of tight areas

• Budget-conscious homeowners

Pros of Flexible Ducts

One of the biggest benefits of flexible ductwork is its lower cost than rigid ducts. Thanks to their light weight and malleability, they are also much easier to install. You can install flexible ductwork in places that are too small or oddly shaped for rigid ducts.

Cons of Flexible Ducts

Flexible ductwork's malleability can sometimes work against it. The ducts require some form of support to prevent sagging. Since they aren't as smooth on the inside as rigid ducts, they may not be as energy efficient.

The biggest drawback to flexible ductwork is that they don't last nearly as long as rigid ducts. Their flexibility can make them more prone to snags and tears.

What Is Rigid Ductwork?

Rigid ductwork is made from aluminum or galvanized steel and has a fixed shape, which can be rectangular or tubular. 

Best for: 

• Homes in areas that see extremely hot or cold temperatures

Pros of Rigid Ductwork

Whether made of aluminum or steel, rigid ductwork is built to last. Unlike flexible ducts, it won't snag, tear, or kink. Since the inside of the ducts is completely smooth, air can flow through them more efficiently, leading to lower energy bills. The ducts are also easier to clean compared to flexible options.

Cons of Rigid Ductwork

The big drawback of rigid ductwork is its price. It costs much more to install rigid ductwork than flexible ducts, and rigid duct replacement costs are also higher due to the complexity of installation.

Rigid ductwork weighs a lot, so it requires more people during installation. A local professional duct installer will also have to cut rigid ductwork to an exact length and ensure that the width of the ducts works in the space.

Flex Ducts vs. Rigid Ducts​

Here's how flex ducts and rigid ducts stack up.

Durability​​: Rigid Ducts

Rigid ducts win hands down when it comes to durability. Thanks to their sturdy metal material, they resist rust and mold growth and can last for decades. 

Price​: Flex Ducts

While rigid ducts win for durability, flexible ducts give them a run for their money. Flex ducts are more affordable, ranging from $1 to $4 per linear foot versus $7 to $13 per linear foot for metal.

Since they have a simpler installation process, the cost to install or replace flexible ducts is also lower than for rigid ducts.

Noise: Tie

Both rigid and flex ducts can make noise while they work. While the shape of rigid ducts can help them direct sound more smoothly and dampen the hum of airflow, you may hear noise if they become blocked or turn at certain angles. 

Flex ducts may also produce noise due to their walls' ability to contract and expand in response to changes in temperature and air pressure. However, flex ducts can also reduce noise if they're made of non-metal materials such as fiberboard or if they're installed at the end of the ductwork system. 

Ease of Installation/DIYability​: Flex Ducts

Once again, flex duct wins for installation ease. The ductwork weighs less, which makes it easier to maneuver. It's also more forgiving in tight areas. Because you can scrunch it, there's more leeway when cutting the ductwork, too.

Maintenance​: Rigid Ducts

Rigid ducts are easier to clean than flex ducts, as dirt and debris are less likely to get trapped inside them. Since they resist rust and mold growth, you don't have to worry as much about cutting the ductwork in place to replace sections of it.

Flex ducts require more frequent cleanings than rigid ducts, to keep dust and debris from collecting inside.

Energy Efficiency: Rigid Ducts

Thanks to the smooth interior surface, air flows easily through rigid ducts, which can help your HVAC heat or cool your home more efficiently. While flex ducts can still heat and cool your home, they do so with slightly less efficiency, thanks to the uneven texture inside.