Events boost the profile of spiral duct in sheet metal industry
The Spiral Duct Manufacturers Association was excited to welcome over 50 members and guests who joined us for our annual winter meeting, held Jan. 29 in conjunction with the AHR Expo in Las Vegas.
Pat Brooks, general manager at Eastern Sheet Metal in Ohio, updated members on the recent flat-oval testing project conducted by SPIDA. Members heard that flat-oval gauge and reinforcement tables will be included in the soon-to-be updated HVAC duct construction standards from the Sheet Metal and Air-Conditioning Contractors’ National Association.
John Reints, owner of StaticRegain.net, was the featured presenter at the meeting. Reints has 35 years of mechanical engineering and contracting experience. Static regain is a duct design method, which takes into consideration velocity pressure, unlike equal friction or equal velocity design methods.
As a mechanical contractor, he converted rectangular duct systems to round and flat-oval spiral duct systems by using the static-regain design method as a way of reducing material and labor costs. He now owns a consulting business that works with mechanical and sheet metal contractors to use this design method to maximize profitability.
Reints detailed the key advantages of spiral duct: lower material and labor cost, less duct leakage, lower heat transfer and less required space. By converting rectangular duct to spiral duct using static regain, he showed the average project reduced weight by nearly 50 percent and reduced labor by 37 percent on six installed projects at various locations across the United States. Savings ranged from 12 percent on a 12,000-square-foot project in Fort Worth, Texas, to 55 percent on a 23,000-square-foot project in Chicago. The average conversion resulted in a 37 percent saving or $306 per ton. Nearly identical results were realized in an analysis of projects in Mexico. An additional cost saving was realized by the building owner with fan energy being reduced 6-30 percent using spiral duct. The use of spiral duct also significantly reduced duct leakage.
Reints presented a graphic from the U.S. Department of Energy demonstrating the importance of duct leakage. Duct leakage was the largest cause of commercial building energy inefficiency, causing $2.9 billion in lost energy costs annually. Conversion of rectangular systems to properly sealed spiral duct offered leakage less than 1 percent of system cubic feet per minute.
Smaller spiral duct, with better airflow, can replace larger rectangular duct, which results in less surface area for heat transfer. In other words, conditioned air loses less of its energy before reaching air outlet diffusers when installing spiral duct. As an added benefit, there is less surface area to insulate, reducing internal and external insulating costs.
Reints addressed the very common complaint, “I can’t use spiral duct because it won’t fit.” He demonstrated that using multiple runs of smaller diameter spiral duct — and in some cases spiral flat-oval duct — he could not only make the duct fit, but could also provide a lower material cost, lower installed cost and higher efficiency spiral duct system in the same space allotted for rectangular duct.
SPIDA’s spring meeting, which took place May 4-6 in Minneapolis, was a chance for representatives from spiral duct manufacturers across North America to discuss common issues. It also included time to attend a Minnesota Twins ballgame. SPIDA would like to thank Sheet Metal Connectors as our host company for this event.
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Scott Witherow is a vice president at California-based sealants and adhesives maker Design Polymerics. He is also on the Spiral Duct Manufacturers Association board of directors.