Exposed spiral round ductwork has become a popular architectural feature in both new and renovated commercial buildings. Seen everywhere from cafes to retail stores, this style creates a contemporary aesthetic.
But is the popularity of spiral ducts just a trend, or are there practical benefits to using them? The answer is a resounding yes; spiral round duct is the preferred choice for significant labor savings, higher energy efficiency, increased performance, and more.
Lower Overall Installed Cost:
The installed cost of spiral round ductwork, including product, parts, labor, warehousing, transportation, packaging, and waste disposal, can be significantly less than that of rectangular duct (in some cases, up to 50% less).
Reduced Air Leakage:
Air leakage at duct joints can lead to energy loss and compromise a system’s efficiency. Self-sealing spiral duct systems can guarantee a system that meets or exceeds the highest industry standards for airtightness.
Energy Savings:
When air leakage is nearly eliminated, the cost of filtering, heating, cooling, and distributing conditioned air is minimized. One study shows that a nationwide shift to more airtight systems could lead to annual energy savings equivalent to the annual energy output of three nuclear power plants.
Lower Pressure Drop:
The pressure drop of air leaving an air handler is typically lower in a spiral system. The spiral design provides equal internal pressure, allowing air to flow evenly and efficiently, which also results in lower energy consumption.
Improved Indoor Air Quality:
Air leakage can significantly impact indoor air quality. Due to concerns about “sick buildings,” there is a demand for more fresh-air intake. With airtight ducts, it is easier and more economical to meet these stricter demands.
Reduced Noise from Pressure Differential:
The problem of noise breakout can be avoided with a spiral duct because the reverberation created by the pressure differential that exists in a rectangular duct does not occur.
Less Space Required for Installation:
With rectangular ducts, up to three inches of extra space must be factored in for the connections and reinforcements needed at each joint, which is not a consideration when installing spiral ductwork.
Less Turbulent Airflow:
The design of rectangular ductwork involves air moving around sharp edges, dampers, and turning vanes, resulting in less turbulent airflow. This airflow obstruction can contribute to noisy turbulence. With spiral ducts, fewer sharp edges result in less noise.
Simplified Cleaning & Inspection:
Many facilities now require regular inspection and internal cleaning of ductwork. The approved cleaning methods for spiral ducts are readily available, economical, and effective.
Easier Air-Flow Measurement:
The periodic task of air-flow measurement for mechanical engineers can be simplified. Many accurate and inexpensive flow-measurement devices specifically designed for spiral ducts enable regular check-ups or continuous monitoring.
Other Sources:
The Efficiency in Round
By Eugene Smithart, P.E., LEED-AP
From the August 2015 issue of Engineered Systems
The HVAC Factor: Spiral Round Ductwork
By Gene Smithart, P.E., LEED AP
From the August 2013 issue of Today’s Facility Manager
Spiral Duct is a Contractor’s Best Choice
By Jeff Rogers, President of the Energy Audit Institute
From the June 2012 issue of SNIPS Magazine
Weighing the Advantages of Spiral vs. Rectangular Duct
By Peeter Vesik, SPIDA Chairman
From the December 2016 Issue of SNIPS Magazine
The Spiral Duct Manufacturers Association (SPIDA)
SPIDA was formed to promote the use of round duct, spiral duct (spiral pipe), and flat oval duct by informing the public of its advantages, supporting testing and research of round duct and spiral pipe, and providing manufacturers with specialized information necessary for the efficient operation of the business of the members.