Going out through the wall to a down-roof style blower should avoid the snow build up issue unless you get snow to the roof line. A roof chase that is very high could get one above the snow.

The only way to keep noise down without room for a silencer is to use an over-sized blower and run it at partial power. Blade tip turbulence noise typically dominates and increases at some power of the tip speed.

Aim for an actual 90 CFM/sq. ft. of hood entry area at max flow. 600 CFM actual should be enough, depending on hood dimensions, and this can be obtained from operating at the 900 CFM (free air) power level, given adequate MUA. If a 1500 CFM down-roof blower is not quiet enough at that flow rate, then a smaller-sized commercial up-blast blower directed horizontally from the wall could be scaled to achieve the desired flow rate at a low fan speed.

You must have missed multiple examples where I have noted that the duct velocity (CFM/area) should be in the 1000 to 2000 ft/min range, so once actual airflow is determined, size the duct accordingly. Larger duct (lower velocity) in this range will reduce duct turbulence noise.

Do not plan the hood system without planning the MUA system.

Kaseki - we do have significant issues with snow buildup on the ground as well. The home is ranch style and eaves overhang about 20” but the roof is currently still metal so the occasional roof slide along with accumulation on the ground actually can almost reach the eaves during a heavier snow year, and we actually have to dig out to maintain good egress for some windows. We did consider ducting out the wall but the overhang combined with potential snow buildup could be an issue which put us back to internal blower. My husband is not keen about any remote blower on the roof as snow slide, even with a cricket of sorts, and also occassional very high winds with snow just deters from that option.

I do remember the posts regarding duct velocity and determining airflow and then duct determination. i think I even printed that info off and handed to my engineer husband who is working with our contractor to design the system. There is a serious lack of knowledge, or just dont want to be bothered wih complication, among HVAC contractors in our rural area and most, if not all, of them deal with newer homes and new construction that have already ’packaged’ HVAC systems - there is little use or demand for engineering and retrofitting odd custom systems. There is plenty of new construction keeping them busy and we have yet to contact anyone willing to think outside the box right now. We are having to do lots of self educating.

With all of that said, I sort of have a big picture now of what all this entails but there are so many choices and variables within the various range hoods themselves and I do want sturdy, easy to clean (baffles, drip), enough cfm’s to keep fumes at a minimum, and as quiet as possible, albeit I am understanding better the variables affecting the sound levels.

Thank you again for your help and input. We have read as much as possible the posts from both you, OPA1, and a few others. We also are using the Greenheck guide which I printed off.

As a further note: If any combustion appliances have their own externally-drawn MUA, then "passive" (no blower) MUA for the kitchen hood is feasible and significantly less complex.

I just found one of the related threads I had remembered but not printed - https://www.houzz.com/discussions/5584148/bluestar-vs-wolf-vent-hood#n=21

Owners seem to like this Zephyr AK7536CS 36" wall-mounted, stainless steel hood. It's 24" deep (same as Bluestar hoods), has a 650cfm built-in blower, and can be ducted horizontally through an 8" round duct. Specifications. Also sold by build.com and Home Depot.