How to Install a Microwave with External Venting

Many times an over-the-range microwave that recirculates cooking fumes can be converted to exhaust to the outside.

Here’s how to go about it:

  • Remove the access plate on the top of the unit in order to reach the motor.
  • Remove the motor mounting screws on the back of the oven.
  • Take out the motor and rotate it 90 degrees, so that the fan motor now blows upward.
  • Attach the transition piece to connect the oven to ductwork
  • Modify the cabinet over the stove to allow the duct to pass through by cutting holes on the top and bottom.
  • Use a laser measuring tool to mark a dot on the ceiling that will identify the center of the hole that needs to be cut for the ductwork.
  • Join the sections of ductwork and seal the joints with metallic tape to secure them.
  • In the attic, mark a spot directly above the duct so you can cut a hole in the roof decking and extend the vent pipe up through that opening.
  • On the roof, tuck the flange of a roof vent under the shingles above the opening and secure it with roofing tacks and roofing sealant.
  • To hide the exposed duct in the kitchen, build a frame around it and cover it with cabinet grade plywood. Cover the exposed edges of the plywood with corner trim.
  • Apply a coat of primer and two coats of the wall paint.

Watch the video for details.

Further Reading


  1. I want to replace an old OTR microwave. Due to the kitchen layout the microwave will be installed on an inside wall. I want to vent to the outside. The old microwave did not. It appears when this house was built provision was made for venting out the rear of the microwave into the standard 2×4 wall, up the cavity inside the wall, then up through duct work in the attic through the roof. I would like to use that path to vent a new microwave. My question – given the cavity would be only 3.5 inches deep plus 0.5 inches for the drywall (14. 5 inches stud to stud), will the damper that is attached to back of a typical microwave significantly block the upwards airflow when the fan pushes it open to exhaust the air? We haven’t purchase a new microwave yet so I am unable to see what the overall depth at the damper will be when pushed open. I do not have the option to vent through the cabinet above. Your advice would be appreciated.

  2. I have an interior wall range with microwave/hood. We wanted to have a replacement microwave/hood dropped lower by 1 1/2 inches and have it vented. Contractor said that venting would have to be through overhead cabinet and run on top of cabinet to external wall with hole punched to exhaust to side. Above the kitchen is a full bath adjoin closet bedroom, so I’m not sure if there is a direct pathway to roof above 2nd floor. Is this a good idea to have vent resting above kitchen cabinets to vent outside?

  3. In the video, you did not show how to connect the duct work to the transition piece or the roof vent. You just skipped over that and showed it as done. How do you do this? ( Showing how to put the cap vent under the shingles does not show how to attach the duct work underneath to it.)

  4. I need exactly what u had demoed in the video. Replace microwave with vent out. Do u have services in San antonio Texas and tentative/approx , what would be the cost to do this ?

    • Hi, Bob, features home improvement advice from the nationally syndicated TV show “Today’s Homeowner” and its experts.
      We don’t offer information on individual home builders, repairers and suppliers, but we encourage checking your local phone listings for this information and project estimates, which vary by location.
      Thanks for your question, and good luck!

    • Hi, Ginny,
      We can’t provide product recommendations due to the constantly changing inventory, but we recommend checking your local home center, asking questions and ensuring the product matches your needs.
      Good luck!

  5. My question is the same as Raymond’s. I need to vent through the wall. The vent was installed for an old microwave which now needs to be replaced. I guess the problem is to find a replacement designed to line up with what I have. Thanks for your advice.


  6. I bought a whirlpool microwave model vml75011HV-4. I had the installer vent it to the outside of my house. However, when I use the venting system it still blows air out inside my house as well as outside. Is this normal and should I have any air coming out of the front of my microwave into my kitchen?

  7. My microwave is installed on a wall adjacent to the garage. We have switched the MW from recirculating to venting and added the metal flange on the back. we have cut the drywall in the garage and now just need to add the proper vent piping or ductwork to get it to the side of the garage to cut an exterior vent with vent cap and bird screen (of course!). What is the proper size vent pipr or ductwork required in Virginia?

    • Hi, Steve,
      Great question! We have forwarded it to the Today’s Homeowner Radio Show’s producer.
      He will contact you soon to discuss featuring it during an upcoming show.
      Take care!


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