I have a microwave with a ventilation unit over my cooktop that vents through the roof. It works ok for what I cook. But I don't cook chinese food in a very hot wok - grill steaks (I use the BBQ for stuff like that) - or anything similar. I doubt the fan would be adequate for cooking like that.

The thing I would be more concerned about is the installation through the attic and roof. Are you dealing with a guy who builds houses - or a guy who just renovates kitchens? It's a big job installing a vent. You have to work around stuff in the attic (HVAC/electrical/etc.). Then cut a hole in the roof which will be bigger than the vent. Then install the vent - sheathing/flashing around the vent (to prevent leaks) - shingles - etc. Our vent is in a cabinet in the kitchen on top of the microwave. How would you propose to hide yours?

You will of course also have to contend with any applicable building codes - permit requirements - etc. (you'd have to submit plans and pull a permit for a job like that where I live).

The only reason I know this is because about 2 years after we built our house - I asked our builder about installing a big vent on our covered porch - which is under our roof - so I could use the BBQ there. And he detailed what would be involved for me. And told me about what it would cost (think it was a little under $2k). It would also create the possibility of giving our leakless roof a new place to leak. I wound up leaving the BBQ outside. Robyn

All good advice.

There have been numbers of recent postings here about these units and some reasonable recomendations on models. I think luv2putt had a thread on this subject a few months ago and several specific models were discussed. He got it for use with his "Racing Red" viking induction range (on which there is an active thread right now.)

The magic search term "OTR" should turn these threads up. OTR = "over the range" and is the abbreviation that is most commonly used.

As part of my incremental remodeling of my small kitchen, I researched replacing my large countertop MW and my range hood with an OTR unit. (I was designing and building a new set of cabinets for the wall above the stove and its countertop). The model I liked was an LG LMHM2017. Like you, I have a small kitchen and was hoping to free up counter space. What I found appealing about the LG was:

(a) it is rated at 400 CFM, which is stronger than most inexpensive range hoods;

(b) it has a "slide-out" extension that pops out to extend over the front burners (most OTRs only cover the back burners); and

(c) It seemed to get mostly good reviews.

I'm not sure that the exact model is still available -- product lines get rearranged so often that it may have a different model number now.

Anyway, I wound up sticking with my range hood and hanging a smaller MW -- a GE Spacesaver II --- underneath the new cabinets. This freed up the counter space and gave more more effective range venting. (When I say "more effective" I mean the Zephyr's centrifugal grease traps had been so effective that I hardly had to do any cleaning on the interior of vent tubing which had been in use for a decade.)

(b) Another factor for me was the height where I had to put the OTR to get clearance over the stove. Partly, this was because I do canning and similar cooking with some very tall kettles. Partly, I was uncomfortable with how high I had to reach to get hot things out of the MW.

(c) Finally, the height also would have created a problem with venting. Because the way the walls were constructed in my house, I would not have been able to use the rear-ward venting to go out the side wall. I would have had to use the top vent and had to go up through the ceiling. Didn't want to do that for three reasons. One of them is that vertical pipes can become a refrigerated cooling column when it gets to -20 degress here in the winter. The other is that there is 20 inches of blown-in insulation in the ceiling above the kitchen. Going through that stuff was way messier than I wanted to deal with. Three was the one shortrobyn identified: punching a hole in an older existing roof was trouble I did not want.

-20 degrees. Yikes! Talk about "your mileage may vary" (lol - sitting here in Florida). I wish our vent would operate as a refrigerated cooling column (but - alas - it doesn't). And since you mentioned weather - our vent does make rattling sounds when we have sustained winds over about 30-35 mph. When I hear that sound - I know it's time to take a look outside - see how the trees are doing. The one thing I'm grateful for is our vent doesn't leak (although it exits through the roof - it has kind of a curved cover area that keeps the rain from falling down it). Robyn