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external vent microwave hood

Update: Avoid Code Violations!

A reader below raised the question of whether I did this duct work upgrade “to code”. I did, but it’s a great point. And along with duct work code, electrical code is key. It saves lives. To see the recent post on common electrical code violations as well a link to electrical accident resources, you should click here.

Venting Microwave Fan to Outside

I like to cook. So, one of the small upgrades that my wife and I have gotten the most enjoyment out of has been venting the over-the-range microwave fan through the exterior wall.  The tools and parts were cheap, the project was fairly simple, and and it has really cut down on the smoke and odor in the kitchen and in the whole house.

We live in a DR Horton house called a “Jordan” in the Greenbrier subdivision in Apex, North Carolina.  The microwave ovens in the Jordan models (and maybe in all the models in Greenbrier) are mounted above the oven/range against an exterior wall.

Ours is a Whirlpool Model No. MH6150XHQ-1, which Whirlpool apparently does not make any more.  Luckily, the previous homeowner saved the Microwave Installation Instructions, including the mounting template, as well as the Use and Care Guide.

Essentially, this project involved these steps:

  1. Unplug the microwave from the electrical outlet hidden in the cabinet directly above the microwave
  2. Dismount the microwave from the mounting bracket
  3. Remove the mounting plate that was screwed into the studs
  4. Cut a hole through the wall (using the ventilation holes in the mounting plate as a guide)
  5. Replace the mounting plate
  6. Switch the direction of the microwave’s fan to blow out the back
  7. Attach a ventilation swing door to the back of the microwave before the duct vent, so cold air won’t blow in from the outside
  8. Remount microwave
  9. Attach a ventilation duct through the outside wall to the microwave
  10. Caulk around the ventilation duct
  11. Plug the microwave back into the cabinet electrical outlet

A couple of key points:

  • I used a special stud/electric wire detector to make sure I was not going to cut though an electrical wire or anything else hidden in the wall.
  • I used a long 3/8″ bit I had from another project to drill holes all the way through the interior and exterior walls in the corners of the rectangle I was going to cut out of the wall.  Then I used a keyhole saw to saw through the drywall first, and then I went outside to cut through the hardy plank exterior.
  • There was, of course, fiberglass insulation in the wall, so I used gloves (and should have used a mask) to remove it from the hole area.
  • I ended up lifting the microwave myself, but it would have been much easier to do this project with two people.

Pros: Now, I can cook fish or bacon in the kitchen (instead of outside on the grill) without smelling up the whole house.  (Also, for better or worse, arriving guests can smell what’s for dinner.)

Cons: I should have done this about 5 minutes after I moved in.

Tools I used (or should have):

  • Safety glasses
  • Phillips screw driver or cordless driver/drill
  • Stud finder with “deep scan” to find electrical wiring or other stuff inside the wall
  • Long 3/8″ bit
  • Keyhole saw
  • Gloves and 3M-style mask
  • Caulk and caulking gun (you can also by caulk that does not need a gun)


  • Swinging door for rear ventilation that supposedly came with your microwave oven.  Our microwave, of course, was installed by the builder, we are the second owners, and have no idea where this part might be.  To find one, you might to jump on line or give the manufacturer a call.  I lucked out.  A very nice salesperson at the big box store that carries a similar model actually just gave me this part from a floor model.
  • The duct piece.

Here are some photos of me going through the process:



Bracket on the wall. (I scored through the smaller bracket holes - unnecessarily - the first time.)

Having drilled the corner holes, I started cutting the whole rectangle out with a keyhole saw, so the rectangular vent duct would fit.

Completed hole from the inside.

Completed hole from the outside.

Here's the fan directed out the back.

This swinging vent keeps cold air outside in winter. You might try Whirlpool, or just ask your friendly neighborhood big box store appliance manager for a spare from a floor sample.

My caulking skills were not very good, but the seal seems to have held.

Installed vent from outside toward the front of the house.


BTW: Dan asks a great question below about doing projects “to code.” But I also wanted to point out that code frequently applies to commercial property as well as residential. And commercial real estate disputes frequently arise, not just over code, but other issues, like adverse possession, eminent domain, and boundary disputes.  If you need help sorting out commercial property disputes, especially if you are in North Carolina, you should click here.