Energy efficiency advantages over metal duct
The Mitchell Park Library and other buildings are demonstrating the fact the fabric duct industry continues to grow and innovate products that improve the delivery of HVAC systems and provide a more efficient, effective, and comfortable environment for commercial building occupants.
Indeed, fabric duct’s superior airflow makes it more energy-efficient than metal duct/register systems, according to a 10-month study performed by Iowa State University’s mechanical engineering department. “Thermal Comparison Between Ceiling Diffusers and Fabric Ductwork Diffusers for Green Buildings,” by Anthony Fontanini, M. Olsen, and B. Ganapathysubramanian, shows fabric duct has a 24.5 percent efficiency differential, because it heats rooms faster and more uniformly to satisfy temperature set points versus metal duct/diffusers. This results in reduced mechanical equipment runtime, saving energy in the process.
As the report outlines, most general enhancements to building efficiency have been a result of changes to the heating/cooling systems, improvements in construction materials, or building design code improvements. However, such approaches neglect the way in which air is dispersed into individual rooms or in a building—that is, the ducting system. This opens up the possibility of significant energy savings by making ductwork systems lighter and better insulating while ensuring cost-effectiveness.
The Iowa State study explores this idea by comparing the performance of conventional ductwork with recent advancements in fabric-based ductwork. Transient, fully three-dimensional computational flow dynamics (CFD) simulations were performed to compute flow patterns and thermal evolution in rooms containing either conventional or fabric ductwork. This analysis was used to construct metrics on comfort and efficiency. A number of different flow rates were examined to determine the performance over a range of operating conditions. Transient finite volume simulations consisted of more than 13 million degrees of freedom for over 10,000 time steps. The simulations utilized high-performance computing (HPC) for large-scale analysis.
The results conclusively showed fabric ducting systems to be superior to the conventional systems in terms of efficiency. Observations from the data illustrated fabric ducting systems heat the room faster, more uniformly, and more efficiently. The increase in performance demonstrates the potential benefits of moving away from conventional systems to fabric systems for the construction of green buildings.
Kevin J. Gebke is the new product development engineer at DuctSox Corp., a Peosta, Iowa-based manufacturer of traditional overhead fabric HVAC duct products. He holds a degree in engineering from the University of Illinois and an MBA from the University of Dubuque. With more than 20 years of experience in HVAC air distribution, diffusion, and movement discipline, Gebke holds 16 patents. He is very active in the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE), and is the author of the “Textile Air Dispersion Systems” chapter in the soon-to-be published ASHRAE Duct Design Guide. Gebke can be reached at kgebke@ductsox.com.
