Spiral ductwork is functional and better-looking than traditional sheet metal or flexible ductwork. It’s an ideal choice, if a little expensive, for architectural design with open ceilings. Often used in commercial settings, spiral ducts have their place in loft apartments and other residential settings where a contemporary or urban vibe is desired.
But what does spiral ductwork cost? When does it make sense to use spiral ductwork vs rectangular ducts?
Fun Fact: The Romans were using a series of tubes connected to a lower-level wood furnace to warm the tile floors in their homes as early as 300 A.D. That may have been the first true ducted home heating system.
About Spiral Ductwork
In 1956 a manufacturer in Switzerland invented a machine to produce spiral ductwork. Spiral duct is a rigid spirally wound tube usually made of galvanized steel, but can also be stainless steel, aluminum or copper. It has its seams on the outside, making the inside surface very smooth and having low resistance to airflow. Spiral ducts can be round or flat oval and are commonly produced in sizes from 3” to 63” in diameter. One manufacturer advertises flat oval sizes from 3” x 12” to a whopping 36” diameter x 124” (12-foot) length.
Where to Use Spiral Ductwork
As noted, spiral ducts are most often found in commercial settings. Warehouses, factories, schools, large churches, movie theaters and athletic venues are a few places where they are often found – but you might have to look for them. When the architect or builder wants them to “disappear,” they are often painted to match the ceiling and walls and also makes them blend in so that we just don’t notice them.
There are two common reasons to use spiral ducts – looks and functionality.
Appearance: In residential settings, spiral ductwork can be attractive when ceiling height is 10 feet or higher and the space has contemporary or urban design. This is true in commercial settings where an “industrial chic” aesthetic is desired.
Function: Spiral ductwork is attractively made, so that it can be “out in the open” if necessary, as we’ve said. This can assist in functionality. When there is no room in the ceiling and you don’t want to install ductwork in unheated or uncooled space (outside, in the attic or garage, for example), spiral ducts work well. They are hung from the ceiling, in most cases. This approach can be cheaper than framing in space for the ducts and creating openings for air vents.
Spiral Ductwork Pros and Cons
Here are spiral ducts advantages and disadvantages.
When compared to either standard rectangular or round ductwork, spiral ductwork has a number of definite pluses.
There are potential downsides to spiral ducts too.
Spiral duct up to about 12” is used for main lines in residential settings – commercial spiral ducts are often much larger, up to 36”. The most common thickness for either setting is 26 gauge metal. The price of galvanized steel spiral ductwork follows. 95% of spiral ductwork is galvanized.
Spiral Duct 26 gauge 4" to 12" in diameter costs $2.87 - $8.77 per linear foot.
Cost factors are:
Spiral Ductwork in Homes - Residential Use
We’ve touched on the aesthetics of spiral ducts. Here’s more information that will assist you in deciding if they are the right choice for you.
There are two main applications for spiral ductwork in the home. The first is the same as it is for other types of ductwork – that is, out of sight. The second is very different from other types – in plain sight. Let’s look at both.
A. Ducts Out of Sight
Spiral ducts can be used to replace existing ductwork quite readily. If they are used to replace the branches off the main trunk – whether rectangular or round – the same size spiral duct can simply be used in place of whatever was used before. If the main trunk (usually rectangular) is being replaced, there will be a flat oval shape of the right size spiral duct that can be used in its place.
B. Ducts in Plain Sight
In the modern home in America, one of the newer and growing trends in HVAC design is that of exposed spiral ductwork. By exposed, we mean just that – the ductwork that is usually hidden above the ceiling or in the walls is actually installed inside the living space of your home where it can be seen.
The fact that spiral can be found in galvanized steel, aluminum or copper means it can accent many different interior design schemes. It can also be painted any color to either match or accent other colors in the home – even a different color in each room.
Q: Why does my current ductwork contain both rectangular and round ducts?
A: Many HVAC duct schemes have a large rectangular “trunk” that connects to the plenum of the air handler where the fan is located for moving the air. Coming off from this trunk are several round “branches” which split the airflow and distribute it to the various rooms in your house.
Q: Should spiral ductwork be insulated?
A: It depends on location. Ductwork in conditioned space doesn’t need insulation. Ducts in an uninsulated attic or crawlspace should be, and you should notice an improvement in climate control/comfort and in lower energy costs.
Q: Is spiral ductwork installation a DIY job?
A: Probably not, for these reasons. Putting the ductwork together is doable for DIY homeowners with good skills. But making sure you have the right size ductwork to achieve the proper air pressure and airflow in your system takes pro-level calculations. Plus, cutting into a sheet metal plenum to form a “perfectly” round hole of “exactly” the right size for the connection is not an easy task.
Using Spiral Ducts
So when should you choose spiral ductwork to replace your existing ductwork? When -
- You want to upgrade to the most energy efficient and quietest type of ductwork available.
- You want to improve the air quality and keep mold and mildew out of your HVAC system.
- Your old ductwork has failed and you cannot access the ceilings or walls to replace it.
Tip: If ceilings are low or standard height, tuck the ductwork up into the corner where the ceiling meets the wall to minimize feeling crowded by it.
When you want to change the interior design of your home and incorporate the look of exposed ductwork.