Thank you both. Let's see if I can be more clear. Our kitchen is decades old in design, cabinets and some wall ovens. When kitchen Ventilation was undertaken, it appears all exterior vented HVAC included not only the over the range or cooktop area vent hood and run but (at least in our house) a 6" diameter vent over the wall double ovens. There are a few GW comments of others who have this arrangement in their older kitchen, some of whom choose not to upgrade from 24" ovens nor change layout because of this vented wall oven arrangement. In my kitchen, the tall double oven wall cabinet with 6" vent on top sticks out like a sore thumb in its location. Very ugly and makes the kitchen smaller in many ways. By removing the soffit above and this tall cabinet, I will open up the width of the kitchen dramatically and make it much more aesthetically appealing. That is why I started this thread to see if the 6" HVAC vent can be capped. I don't want to keep the wall oven cabinet (nor move it to the side a bit) as it affronts me so badly where it is. Regarding the current over the cooktop HVAC arrangement, I have a decades old Thermador 42" under-cabinet vent hood, back draft damper and then a 3 1/4" x 20" w x 47" h enclosed galvanized steel rectangle box running up behind the shallow 36" width cabinet to a 14" soffit. I'm still trying to figure out the very top of the venting directly behind the soffit itself and under the ceiling. It's a maze of galvanized steel as I crane my head up through those 3 1/4" by 20" holes with a LED flashlight. As I see a curvature of the galvanized metal on the back of the cabinet side, I suspect they may have installed a 3 1/4" x 20" 90 degree Elbow Round. There appears to be a box like opening on opposite this, on the back kitchen wall at this height/location. Problem is, I can't measure this opening, can't probe it with my pull out tape measure to see if it's 90 degrees, and can't fully visualize it. All I know is this is where the ventilation moves through, and that eventually a long run of 10" round duct goes into the 1000 cfm Thermador centrifugal fan on the exterior side roof (I climbed up to the top of the addition and removed screen venting to peak in and yep, there was the round duct leading to the exterior fan). When the soffit comes down I will see the truth but in the interim I am planning a new vent hood and replacement of all the kitchen visible galvanized steel that can be done. Still, I'm not going to tear out walls to change the run: that's what I inferred about using the run as is, exiting the kitchen proper onward but to a new exterior 1000 or 1200 cfm blower. And modifying the electric turn switch of course from the current infinite 6 amp to whatever the new specs on the selected blower require. Our house is not overly tight and yet I am planning on the Broan MUA adaptor (can't recall model number off hand). I have a goodly amount of electrical panel open (200 Amp total) which is a benefit. Thanks for your help. I hope it's clearer now. This post was edited by SparklingWater on Sun, Jan 27, 13 at 16:45

wdccruise/dadoes - thank you but I’ll most likely get someone else to do it mxk3 - for a number of reasons, main ones being that I miss the efficiency of a vented dryer and I hate the way the dryer adds heat to the apartment. We originally had a Miele stacked, vented unit that was superb. They worked beautifully until the dryer gave up after 15years. Miele couldn’t fix it and recommended we “upgrade“ to their new ventless model. They also recommended we replace the washer although we had no issue with it. As we’ve always used Miele in different countries and trusted their appliances we went with their new ventless dryer/washer combo (t8023/w3038) despite misgivings about a ventless unit in an nyc apartment. The washer is fine but the dryer is frustrating to use as it takes longer to dry clothes, adds heat to the apartment and generates a layer of fluff/lint into the apartment. The dryer broke down 4 times in the first year of use and they replaced it. Their customer service was also very disappointing. I seem to have gone off on vent (!) about Miele when you only asked why we were planning to switch back! Hope I answered your question anyway

That's some improvement and you had a short run to outdoors to start with. Probably will see a bit more with 'normal' mixed loads. Looks much cleaner & will be lots easier to clean. I replaced about 4' of semi-rigid flex with solid, changed the louvered vent outside with a ball seal (Lambro Vent Seal) and got the vent actually connected to the outside vent opening. DH had installed it originally; the tubing was not even connected to the tailpiece of the exhaust on the outside of the house! And no tape. Was a bit of a nightmare getting it connected because it exists thru the rim joist. So I had to work back in the recess over the foundation with floor joists over my head. Got it connected & taped up now. The space was so limited that I had to use 4-6" long pieces of tape to seal the joint. Combination of about everything that could be wrong was wrong. The periscope gained me about 2" of floor space, too. Which was huge given how tiny the laundry area is. Looks much more tidy and the reward was a big reduction in dry times.

I used a company that did dryer vent cleaning and repair - might have even been that Dryer Vent Wizard. They did an excellent job correctly reinstalling my vent which was never done correctly in the first place. I'd recommend someone like that if you have them in your area. ETA: just checked - it was Dryer Vent Wizard that I used.