Spiral & Flat Oval Duct Work

Energy Efficient

Ductwork leakage is always, and rightly, considered as the single biggest source of causing the maximum additional energy use in the built environment. Based on a survey of predominately rectangular duct systems, the annual cost of this energy waste runs into the cores of rupees. Design Engineers, code officials and building owners(users) are taking notice and questioning the use of ducted HVAC systems. There is a simple ducted solution, factory fabricated spiral/ flat oval duct, and fittings. It has long been recognized that spiral/ flat oval duct systems leak a great deal less than comparable rectangular systems.

This can be easily explained when looking at the source of leaks, seams, and connections. First, let’s consider the seam. Rectangular duct seams, such as a Pittsburgh Seam, require sealants for efficient sealing, either during production or at job site. Spiral seams, on the other hand, require no sealing and this is recognized by ASHRAE Standard 90.1. The testing shows leakage rates so low as to be inconsequential in case of spiral duct.

The second source of the leakage is the transverse connection. Rectangular duct joint comes at ever 4 feet interval in addition to fittings (elbows & tapers) as required to change size or direction. Spiral duct can be manufactured in lengths up to 12 feet long. Because of this length difference, and taking into consideration the number of fittings required, 30% or more of the transverse connections can be eliminated. Careful use of factory mounted branches on spiral duct can allow the elimination of almost 50% of field connections. In other words the use of spiral can eliminate the opportunity for leakage by almost half. Overall even SMACNA, whose members make large quantities of rectangular duct, admits that rectangular duct can be expected to leak at least twice as much as spiral round and flat oval duct. If the Pittsburgh seams aren’t sealed, you can expect rectangular duct to leak four times as much.