Venting a microwave outside requires installation of duct work to an outside wall or a roof. Use the code and installation instructions from the manufacturer of the over the range microwave oven. The video addresses what kind of duct work to use, the length of the duct work, how to seal it and much more.

There is also a Know How Now video showing how to install an over the range microwave here's the link:    • Install Replacement Over the Range Mi...  

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