Sorry I can't help. Maybe you should also post this over in the appliances forum??

If you're lucky enough that the range is on an outside wall, I suppose an old style wall exhaust fan would work, in theory. Whether is meets today's codes and whatnot is something you'd have to check. Otherwise, the only other option seems to be removing the cabinets above the range and putting in a hood

I wonder if you could put one of these in the upper cabinet and a metal liner on the bottom of the cabinet. The guts of the fan sit inside the cabinet, and they are not huge.

Not on outside wall and the microwave is in the overhead cabinet. I could move the microwave AND cabinet but would still have to vent and cut a hole thru the ceiling. I have soffit to ceiling over all cabinets so that presents another problem. I really like the look of the above flush unit but I still would have to run the duct which wouldn't be cheap and the microwave would take up space. I am a kitchen guy,but the only thing small about my house is THE KITCHEN. Where I live I don't have to worry about codes. I might use part of the above suggestion and just put a piece of metal under the cabinet and forget venting. All of my frying and most of my major cooking is done outside ie:smoker, Webber Summit, 18 quart Nesco roaster oven, huge fish/turkey fryer. Do it all on my screened porch. Have a huge sink, TV, cabinets, garbage disposal, refrigerator,etc out there. If I conciously was aware of my situation and careful. What do you folks think ? Can I get away without venting to get what I want ?

Wonder if you could switch out your upper-cabinet microwave for a microwave hood. That way you would at least have some exhaust system in place.

What is your goal in adding a hood: fume and smoke exhaust, asthetics, etc?

busybme. Do microwave hoods have to vent to the outside ? Or can they be recirculating ?

You can get hoods that are recirculating but they are frowned upon by the folks here. Really depends on your cooking. If you do a lot of frying, stir frying which generates more heat, grease, smoke then recirculating is not the best way to go. We bought a Broan hood that can be vented vertically or horizontally but can also be used as recirculating with the use of special filters you must buy. We chose this because we started before winter. DH did not want to vent out into the roof with the cold and snow. Right now, we have the special filters and it is being used as recirculating. When weather gets nicer DH intends to vent out to the roof.

To answer the OP's question - yes over-the-range microwaves just recirculate the air back into the room. I think that would be your solution.

Another thing you should know is that the manufacturers of most downdraft hoods do not advise or warranty installation behind a range of any sort. You need to expect it to be difficult to find a downdraft hood that fits under a cooktop with an under counter oven.

They do make convection/micro/speedcook over the range hoods and it might be more appealing to you or give you more choices in ranges since you could pick out a single oven unit.

Over the range micros can generally be installed to either vent or recirculate. In some of them, the hood component moves over 400 cfm. If you don't do a lot of frying and aren't looking at a high btu range, 300 cfm or over should be ok and there are plenty to choose from.

I believe that you can not use an over the range hood and vent downwards - if you were thinking of somehow connecting the ductwork up to something like a microhood.

If you are not required to vent by code I suppose you would get some trapping of grease and some reduction in cooking smells from the charcoal filters inside the hood.--But maybe you could do without anything. I don't know of anyone personally who has ever changed the filters in their recirculating hoods, so I wonder if they are really doing much at all.

The soffit could actually work in your favor although it would require some demo. My vent pipe, as well as my downstairs neighbor's and my downstairs downstairs neighbor's all run through the soffit above my kitchen cabinets for at least part of their journey. Could you go across the top of you cabinets and out a side wall that way?