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Article content provided by Johns Manville.

High-quality insulation for a spiral duct without the need for a double-walled system? A cost-effective option made to specifically and accurately fit round ducts better than V-grooving duct board?

Yes! Johns Manville’s  Duct Liner is the answer.

We know how labor-intensive installation of a double-walled system is, and how heavy and expensive it can be. That’s why we created , a fiberglass spiral duct liner solution that’s been specially engineered and tested to thermally and acoustically insulate the interior surfaces of round ducts, without needing a second length of metal duct.

The biggest benefit of using  over a double-walled insulation system is that it’s often a substantial cost savings. Installation is much faster and simpler, saving on labor costs. There’s less connecting of duct pieces, you don’t need the spacers necessary for a double-walled system, and because  is lighter weight, labor is less intensive for installers.

“We see the trend going more and more toward spiral ducts,” said Cassie Todtenhagen, Product Manager. “They’re more efficient for airflow, since there’s less friction loss around corners. And aesthetically, they’re nice to look at. But a double-walled insulation system is expensive and time consuming. It’s very labor intensive, welding the inner and outer metal pieces together and is very heavy.  is a much simpler and more cost-effective solution in many cases.

”Spiral ducts are very common in today’s commercial settings. Benefits include longer duct runs and reduced leakage because of fewer joints. For designers looking for both thermal and acoustical control, a single-walled system can be used in conjunction with a duct liner. And in a spiral duct,  is the perfect solution.

 products are pre-kerfed and coated with JM’s Permacoate® acrylic coating, protecting the airstream surface. The liner needs to conform to the curved inner surface of the duct, so factory installed kerfs are cut at specific intervals, depending on the duct size, to ensure a proper, snug fit.

JM recommends using  instead of V-grooving duct board, as it is specifically engineered to avoid the problems that can happen with V-grooving. Competitive systems that use a mat-faced, fiberglass duct board (designed for rectangular ducts) use V-grooving blades to remove strips of fiberglass, leaving gaps in the remaining product so that the board can be rolled for insertion into a round duct. V-grooved duct board includes a mat facer that is cut into thin strips that can delaminate from the product and enter the airstream. Additionally, the surface is not as smooth, and additional coating can be required for any exposed cut in the duct.

The factory-made kerf cuts in  result in a smooth fabricated surface, with acceptable surface roughness and surface profile in testing. The main benefits to using Spiracoustic Plus over V-grooved duct board are the improved product performance, ability to line ducts as small as 6”, no glass mat delamination concerns, and reduced labor from manufacturing the V-grooved product and touch-ups that are required.

So on the next spiral duct you specify or install, consider whether  will work for you. It could save you time, energy and money – a win for everybody.

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Have a question for Johns Manville? Contact Johns Manville .

Johns Manville supports contractors with productivity-enhancing and performance-enhancing mechanical products, including duct, pipe, and building insulations.