Photos would help. Pls post some.

There are two types of range hoods that deal with cooking steam, odors and smoke: ducted and ductless. I'm guessing you want to put in a ducted hood where the microwave is now. These are usually superior for keeping interior air clean, but they require access to the exterior of the house. If you can't go through the wall you have to go up then out. But you don't have to go straight up. There are OPTIONS once the pipe enters the ceiling joist area. The exhaust ducting can go up through the attic and roof, be turned to exit at a better location of the roof, or it can turn 90º and run between the ceiling joists to an outside wall vent. The bottom of the hood should be at least 24" above the range top, so you might have to remove the cabinet above the microwave, but you can run DUCTING THROUGH CABINET, though you will lose storage space.

If none of these possibilities will work in your space, there is still the ductless hood. These pull steam, etc. through a filter and the cleansed air is recirculated back into the kitchen. Obviously they don't help with removing heat from the kitchen, and the filter does require CLEANING. Ductless hoods are much less expensive to install, because there are no ducts to install or cabinetry to remove.

We just remedied the exact situation you describe. The crazy person who designed this house thought it a good idea to put the range in the smack center of the residence. We are the second owners, and we struggled for over a year to find a viable duct path to get external ventilation in our kitchen. The OTR microwave was pulled out and replaced by a hood with ductwork running up through the cabinetry, over the cabinet tops (hidden inside a new soffit), through the pantry, and to an inline fan in the garage, which exhausts the air outside of our garage. Installing this new ventilation path was this most expensive part of our kitchen reno, and the entire reason we even had to do the kitchen reno! Totally worth it! We love this change!

Pittsburrito, wow, well done! Thank you for your post. It’s like home designers believe it is just the way kitchens are arranged today. It’s funny, around my area modest older homes are more likely to have a proper vent over the range than the vast majority of new homes. Partly, I guess this is to provide the “breakfast nook” area with windows, but the end result is a kitchen with no external wall. And I feel pretty sure new home builders would not go to the trouble and expense you guys did! Just stick a microwave there!

Mind shift, thanks for the helpful post. I am indeed referring to ducted. Also, for some reason your post does not show up on the version of Houzz I have on my ipad☹️. I currently have a telescoping hood behind my gas cooktop, ducted under the house and out, but it is for all practical purposes, useless. I was told at the time it was “almost” like having an overhead hood. We are new home shopping and I refuse to go that route, or have the microwave over the range. Which severely limits my options! So I am investigating whether retrofitting a kitchen is a viable option.

@momdino, distance adversely affects air flow efficiency as does an elbow (direction change). Smaller ducts are less efficient than larger ones. You can add an inline fan to boost air flow, but most are intended for HVAC applications. A centrifugal (aka squirrel cage) fan has the motor outside of the air flow, which would keep the motor clean of accumulating grease, and less likely to be a fire hazard. Perhaps an HVAC supply store would know of one that could be installed near the exhaust point of your under-house exhaust, but this is strictly a postulation. Replacing the microwave with a ducted hood is a surer fix.

@pittsburrito, you made good points about the positioning of exhaust venting in hew homes. I suspect that part of the problem is the size of new homes. While it makes sense to put the washer/dryer near the bedrooms and bath where most laundry is generated, the location is likely to be near a central hallway instead of against an external wall. Any dryer duct is going to accumulate lint due to the humidity it carries, and even a short duct will clog up. You are smart to clean it every year.

Your microwave is probably able to be converted from ductless to ducted. If you don't have the original installation paperwork, check the manufacturers' website. It's usually a simple matter of flipping the fan motor so that it exhausts either up through the ceiling or back through an exterior wall, instead of blowing through filters and back into the living space. That said, the location of your range may make ducting to the exterior impossible, because of distance and turns.

Middle of the house kitchen...easy enough to vent a hood out the roof provided there is attic space above the kitchen. Randomly possible if there is closet space directly above the stove. Alternatively, not ideal, but possible to run vent pipe behind soffits to terminate on an exterior wall.

**ETA a vent could be against a blank wall on the second floor enclosed in a framed & drywalled chase. Or left bare/ painted but that would be an industrial/ steam punk thing acceptable in a loft, etc., not typical residential subdivision.

You have to take it case by case seeking the shortest possible run with the least amount of turns/ elbows. So it can range from being relatively easy to impossible.

Ci_lantro, Most houses around here are two story, so I was concerned that unless the vent hood could be located close enough to an outside wall, you were out of luck. Thanks everyone! Your suggestions and comments are certainly helpful and have opened my mind to possibilities.