If you look at the Modern-Aire site, they have several shapes where the front tapers at the top to the depth of an upper cabinet, and the sides are straight so as to butt up to, and cover, the yellow cabinet sides you mentioned. Their typical sizes are 18" and 30" high, but you could get a 24" custom one if your budget allows. Or you could get an 18" and have a box made for above it to cover that area and to which you could attach replacement moulding. The box could be made of either wood matching your moulding or sheetrock. Vent-a-hood has a stainless direct replacement if you decide to stick with the same size you now have. I'm attaching the link to the Modern-Aire page that shows their shapes. PS-10, PS-11, and PS-26 all have the characteristics I was talking about above. Here is a link that might be useful: Modern-Aire Hoods

Hello Houzz Community! I found this thread when Googling a similar topic. I'd like to replace my under cabinet hood with a wall mounted hood, and yes I know I have to remove the cabinet above the current hood which I'm fine with (see photo). My existing under cabinet hood vents out the wall to the side of my house - see photo, and note the vent is not blocked by those shrubs, there is space around it, you just can't tell from the angle of the photo :-) So my question is....can a wall mounted hood be installed to vent out the existing vent in the wall, or does a vent need to be created in the ceiling? Also, what type of professional can help answer any related questions I have about this? Would I ask the wall mounted vent manufacturer? Or a handyman? Thank you in advance for any guidance! I am a newbie homeowner and am learning as I go, so truly appreciate you taking the time to share your knowledge with me!

When moisture and grease particulate laden air flows through a duct, there is turbulence and these two components will be brought in contact with the duct wall. Slow moving air will allow condensation; fast moving air will allow impingement collection. In general, both likely happen at different ratios depending on temperature and fan setting. I wouldn't change a duct diameter just for this reason. What you have for a hood is unconventional. Commercial hoods and "pro" residential hoods use baffles that cause two 180-degree turns in the air flow. The larger grease particulates are deliberately impinged on the baffle surfaces, and given some baffle angle will drain toward a collection point. Even without angle, the grease is trapped where it can't easily drip down onto the cooktop. I don't know the details of this fan scheme, so I won't comment on what it might be doing with grease. When you initially wrote that you were having the hood installed, I didn't bother with commenting on its design -- sorry. Whether grease dripping from the fan grid was intended or not I cannot say, but it likely is consistent with the physics of the hood design. Again let me pontificate for this forum that the farther a residential hood deviates from long-time optimized commercial hood design, some portion of performance and efficiency will be lost. Running the fans for a minute before generating any greasy effluent might help with condensation, but I think the fan blades here are causing grease collection around the grill as well as wherever it is supposed to collect.

It is actually desirable that the hood capture area be extend some distance from the wall, preferably more than 20 inches, such that it overlaps plumes generated from front burners as well as from back burners. Front-to-back limits due to sight lines to back burner pots need to be considered. An example is the Wolf Pro Low-profile hood that is 22-inches front-to-back, probably 20 inches of effective capture area. It is 10 inches high, so one might want to jack the cabinet over it a bit higher to get 30 to 36 inches of clearance. Spaced out 3 inches for a smooth transition to the cabinet doors one would have very good overlap in the forward direction.