We are replacing an old hood with an over range microwave where the circular vent hole is dead center in the cabinet above. The microwave we just purchased has the designated hole towards the back and is shaped like a rectangle. The duct is also not flexible.

2 things... Would we have to change out the entire duct for a flexible duct?

How would I go about patching the circular hole to prepare for the rectangular hole for the new vent?

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1 Answer 1


No one ever has to use flex duct. You simply need an adjustable elbow (or possibly two) to act as an offset, and a 3x10 boot (or whatever your unit calls for) to terminate.

How you patch the cabinet is at your discretion. If you position the duct boot properly it's not required, but I imagine you'd want to clean up the cabinet floor for appearance and convenience.

  • You're very welcome. "Thanks" comments aren't necessary, though.
    – isherwood
    Commented Nov 28, 2023 at 16:03

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