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Updated by infochameleon on Jul 13, 2023
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Top 5 Reasons to Choose Spiral Round Duct Over Rectangular Duct

Rectangular duct may be an HVAC classic, but spiral round duct is constantly proving to be a superior option in all kinds of ways!



When deciding between spiral round duct and rectangular duct for an HVAC application, one thing to consider is weight. Spiral round duct is typically lighter than typical rectangular duct, because it requires about 30 percent less sheet metal to manufacture. This can be beneficial in a lot of ways, most having to do with cost. Because spiral round duct can achieve the same airflow rate with less metal, it is cheaper to produce and cheaper to transport than rectangular duct.


Cost of Labor

Spiral round duct is easier and cheaper to install than rectangular duct, so choosing spiral duct for an HVAC application is a good way to cut down on labor costs.


Less Leaking

Rectangular ductwork is notoriously difficult to fully seal against leaks, because of the way it is shaped. Conversely, spiral round duct is very nearly airtight, because it doesn’t have longitudinal lock seams, and it needs fewer transverse joints than rectangular duct. As a result, spiral round duct has very low leakage rates when compared to rectangular duct.


Less Noise

Spiral round duct has better pressure drop characteristics than rectangular duct, and is also more rigid. These two factors combined help prevent the loud drum effect often caused by vibrations in rectangular duct. As a result, spiral round duct produces significantly less noise than rectangular duct, which can be a huge selling point, especially when installing an HVAC system in an environment where excessive noise could be disruptive or detrimental.



Spiral round duct is much more efficient than rectangular duct. This is because spiral round duct has less surface area than rectangular duct, so when air moves through it, less friction is created, and as a result, less energy is lost. Additionally, the greater surface area of rectangular ductwork allows excess heat to escape through the duct walls, which is another way spiral round ducts are more efficient.