My microwave oven is mounted to an exterior wall above the stove.
Venting microwave through wall stud in way.
Studs run vertically through a wall.
Get a dryer vent going from outside to inside of the house.
Total distance is about a foot performance will be barely compromised.
I saw this done on this old house when they installed a new microwave hood on an outside wall.
This usually takes two people.
But the builder just left the microwave s fan blowing back into the kitchen.
If you don t want to cut the stud install 2 rectangular ducts on each side of the stud and split the original duct into two.
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.
Basically i would start by breaking out the drywall around the proposed opening and that stud in the middle.
A stud in a wall supporting or otherwise can be cut and boxed.
From microwave up into the cabinet is what you have now.
Option 1 results in a very twisty exhaust path while option 2 is obviously a ton of work.
Photo of unit installed it was heavy and bulky.
It is designed to work like a hood.
First double check that your floor joists are lined up well enough that you can get a 10 duct through the floor where you need it.
I fixed it so that now it vents the kitchen smoke and odors through the wall and outside.
Connect it all with a piece of flexible dryer vent hose.
Sacrifice the cabinet above the stove by snaking an exhaust duct up from the hood over to one side of the stud and then through the wall.
The manual for the microwave says to absolutely not use flexible ducting.
If the two rectangular ducts have a combined area greater than that circular one you wont have issues with flow restriction.
Attach two flex elbows and steer around the duct and straight out the wall.
I d cut a generous square at the bottom of the wall so you can cut out the plate in the stud bay.
Use 3m flashing tape or vycor or tyvek tape to assist ensure that water will not enter the building envelope.
You will have to remove quite a bit of drywall and most likely that wall cabinet directly above the oven.
Buy the sheet metal boot that converts from 3x10 rectangle on the top of the otr microwave to 5 or 6 inch round duct.
Just use flexible dryer vent and be done.
Think of an turning into a line with a box in the middle.
If a floor joist or a beam is massively in the way you ll need some custom ducting or cancel the job entirely.
Can anyone think of any other options.
Line up microwave to duct and connect by placing it on the wall bracket or connecting bolts above.
Install exterior vent hood utilizing proper exterior installation techniques applicable to your siding material.
Basically tear down the wall to install a header saddle jack studs etc.