Sandwiches and Dual Layers: Insulating Ducting Choices


The insulated duct is the perfect addition to any cooling and heating systems. What you may not have considered was that there are two main construction methods to choose from. Imagine! These two styles, Sandwich and Duct-in-Duct, have different manufacturing processes. This means that depending on the specifics you require, one or the other may be a better fit for your situation. Let’s get into it!

Sandwich Ducting

While less delicious than your standard “sandwich” (I could go for a nice Reuben right about now), sandwiched insulated ducting is the easiest to manufacture. The duct material is cut so that two sides are created, with a portion of the insulation material between the two. Each side of the material is sealed on one of our RF welders, creating a sealed and sandwiched piece of insulated material. This material is then processes through the ducting machine as any other material is.

The only drawback to sandwiched insulation in the seal area; there is no insulation at the edge strips. This is somewhat remedied by the fact that this side seal is where the final duct seal is overlapped, increasing the layering at these points to four layers of duct material (as opposed to the two layers of duct material and one layer of insulation material that exists between the ducting seals).

Duct-In-Duct Ducting

That’s a lot of “duct”. As you can probably discern from the name, this type of insulated ducting is made by taking a smaller diameter duct and inserting it into a duct with a slightly larger diameter. The insulating layer, normally made from bubble-plastic sheeting, is wrapped around the inner ducting. Ducting on the inside is reinforced with wire to help it maintain its shape. While this makes for a tight fit, the insulating properties are greatly enhanced.

This style of ducting tends to be shorter than sandwich style simply due to the manufacturing method. Over a certain length, the insulation begins to bunch up and even layering can’t be achieved. To make assembly easier, the outer duct isn’t created with wire reinforcement. This keeps the outer layer pliable and easily manipulated.

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Insulated Ducting is made with wire reinforcement, keeping the duct in shape no matter where it’s installed. Sandwich ducting has this wire added while the duct itself is being fabricated. This puts the wire within the four layer seams, and can still have wear stripping added for extra protection. Duct-in-Duct is made with a standard wire reinforced duct on the inside, and doesn’t need additional wire on the outside. For more information, or to talk with our sales associate about ordering, give us a call at (888) 324-0654.