PRODUCTS CAPABILITIES PROJECTS ABOUT SPOT CONTACT US SPIRAL FLAT OVAL SPIRAL PIPE OF TEXAS PRODUCTS Spiral Round Duct Spiral Flat Oval Duct Rectangular Duct Specialty Duct Connectors CALL US TODAY 817.877.3543 HOME/PRODUCTS/SPIRAL FLAT OVAL DUCT SPIRAL FLAT OVAL DUCT Previous Next Spiral Flat Oval Duct Downloads: Available Flat Oval Sizes Flat Oval Fittings Insulated Flat Oval Checklist Submittals Request a Quote It’s Not Rectangular Duct With the Corners Rounded Off Each year we look at thousands of commercial HVAC duct systems with design concepts that are stuck in the 1980’s. These designs have been costing building owners — and installing contractors — millions of dollars in operating and installation costs. All because of one simple graphic that appeared on page 2.4 of the 1990 SMACNA HVAC Systems Duct Design manual that appeared to support the “common knowledge” of the time. In comparing a simple duct system — 40’ of straight duct, a 90-degree elbow, a transition and three installed taps — it suggested that the installed rectangular duct section ($775 to $1375) was less expensive than the installed flat oval duct section ($975 to $2100). After 25 years and thousands of real-world cases where that suggestion was proven to just not be true, we are still battling the 80’s mentality that “flat oval is too expensive”. But a lot more than just the “cost” has changed in the last 25 years. If just one of the following statements is true about your upcoming project, you need to immediately change your design to one using round and spiral flat oval duct. I have an AHU external static pressure of 2” WG or more My system is relatively free of obstructions and follows the most efficient layout My local energy code follows ASHRAE Standard 90.1-2010 or later I have concerns about sound Except where needed for noise control, I prefer ducts to be externally insulated to prevent future environmental concerns and make duct cleaning easier I would like the ducts to be as small as practical I’d like to follow the ASHRAE Advanced Energy Design Guides for my application I don’t want excessive duct leakage I want the least expensive duct system I care about what a duct system costs — to install and to operate If yours is a commercial HVAC project, you probably answered yes to most, if not all, of the above statements. We are going to give you the reasons why spiral flat oval duct is your best choice to satisfy each of those concerns: Why Flat Oval Duct? Construction Efficiency ASHRAE Noise Insulation Leakage Less Expensive Pressure and Duct Construction Most designers require that duct construction follow the SMACNA HVAC Duct Construction Standards. That manual is an excellent structural guide for building ducts and follows a simple premise — what is the minimum metal thickness and reinforcing to limit wall deflection to a specific amount? Round spiral duct has no wall deflection in positive pressure, but both rectangular and flat oval ducts have flat surfaces that will deflect. Flat oval will have less than a comparative rectangular because you can subtract out the curved sides. You also have those 4-ply spiral lockseams every 4 ½” to help break up the flat surface. But the reason we bring up “2 in. WG or more” is that static pressure determines how much deflection a duct surface will have. The SMACNA manual has gauge-deflection charts for seven different pressure classifications for rectangular duct — ½”, 1”, 2”, 3”, 4”, 6” and 10” WG. But only one for spiral flat oval duct — 0” to 10” WG. So unlike rectangular duct, if you follow the SMACNA standards you will need to use the same metal gauges for ½” WG pressure as you do for 10” WG. Material costs greatly affect the installed cost of a duct system, and a one-even-gauge difference amounts to around a 20% weight difference. The differences between rectangular weight and spiral flat oval weight can be substantial in the “low pressure” range, but things start to even out in flat oval’s favor as the pressure class increases. So the choice should be clear. Round spiral duct is the best choice for duct construction, but if you don’t have the room, flat oval is still a better choice than rectangular duct. So if you still look at spiral flat oval duct as an expensive rectangular duct with the corners rounded off, you need to move out of the 1980’s and see the changes that have taken place in the last 25 years. Proudly Made in Ft. Worth, Texas Available heights of 3” to 36” minor axis. Available widths of 15” to 129”. Available in single-wall and double-wall. Contact our sales department or your local Spiral Pipe of Texas rep for additional information or quotations. We want to be your source for flat oval ducts and fittings. Submittal Downloads 1995 SMACNA Standards – Spiral Pipe and Fittings Oval Single Wall Oval Double Wall 2005 SMACNA Standards – Spiral Pipe and Fittings Single Wall Positive Pressure to 10" Double Wall Positive Pressure to 10" OUR PRODUCTS Product Guides Download and view our Catalogues, engineering info, submittal forms. LEARN MORE OUR PROJECTS Success Stories View our partial list of projects completed and published articles. LEARN MORE OUR EXPERIENCE Traditional Craftsmanship Since 1981 Spiral Pipe of Texas (SPOT) has been “AMERICA’S SHEET METAL SOURCE”. LEARN MORE HOME PRODUCTS CAPABILITIES PROJECTS ABOUT SPOT CONTACT US Copyright © 2021 Spiral Pipe of Texas Digital Marketing by Visual App Spiral Pipe of Texas will be closed November 25th and 26th in observance of Thanksgiving. SPOT will resume normal business hours on Monday, November 29th. HOME PRODUCTS CAPABILITIES PROJECTS ABOUT SPOT CONTACT US