Anyone who is beginning the process of installing a new HVAC system has one very important question to answer: spiral pipe or rectangular ductwork? Spiral pipe and traditional rectangular ductwork are both common choices for many HVAC applications, but which of the two will best suit your needs? If you find yourself asking this question, here are some factors to consider.


Rectangular duct typically has two longitudinal lock seams that traverse its length, and several transverse slip connections. As a result, it tends to leak. Because spiral pipe lacks longitudinal lock seams, and generally has fewer transverse joints, it is nearly airtight, and leaks much less than its rectangular counterpart.



Rectangular ducts tend to have higher pressure drops than spiral pipes due in part to their sharp turns. This makes rectangular ducts less efficient than spiral pipes, which allow air pressure to equalize, and therefore have lower pressure drops.


Rectangular ducts can create excessive noise as a result of duct vibration. Because spiral pipes are more rigid than rectangular ducts, and have superior pressure drop characteristics, they are able to operate much more quietly.


Spiral pipes have a smaller surface area than rectangular ducts, which means less friction is created when air moves through them, and consequently, less energy is lost. The comparatively low surface area of a spiral pipe also helps it conserve heat, as a greater surface area allows for more heat to be lost through the duct walls.



On average, using spiral pipe for an HVAC application is significantly cheaper than using rectangular duct. Spiral pipe is more cost effective to manufacture than rectangular duct, is easier (and therefore cheaper) to install, and is more energy efficient, which contributes to cost savings in the long run.

Overall, spiral pipe offers several significant advantages over rectangular duct. If you want to learn more about our hvac spiral pipe, and how it compares to rectangular duct, contact Spiral Manufacturing at 763-755-7677 or send an email to