Duct Questions

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New Member
May 23, 2023
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A few years ago my HVAC guy told me I could move an ac duct that's inside a closet taking up space into the wall next to it.

That day has come but he's retired. Does anyone know what kind of duct/what size duct would fit inside a wall cavity? It's taking air from the attic above the second floor down to the first floor. My contractor said he can install but I have to supply the duct.

Do I have to do a rigid duct? Do they make a flex duct that fits in this space? Please be specific what it is called so I can find this product.

I supposed I also need a part that goes from a full size duct and converts to the in-wall duct. Thanks!
I'm not a HVAC tech so I'm not in tune to all the products that are out there. That said, I've never seen rectangular flex duct to fit into a 3 1/2" wall cavity. They do carry premade metal duct to fit into the 3 1/2" x 14 1/2" wall cavity between two studs. It comes in two pieces and snaps together.

What is your "regular" duct? Flex, metal, fiberglass, round, or rectangular? They make transition pieces.