I am linking to a very good thread going on right now about ventilation that might help you out. Hopefully some of the experts on that post will chime in here to help with your question. Good luck! This hood stuff is confusing.

Here is a link that might be useful: Ventilation Post

Capture area/size works although 54 inches would be ideal amd CFMs are just fine IMO although with a grill, I would opt for 1500 but that is just me. As to noise? In a word YES! Remote is measurably quieter. You probably cannot get a 1500 CFM internal blower either.

If you told me you had a 48 inch hood and 1200 CFM REMOTE blower, I would say go with it and you would be fine but if noise is a real concern??? then...its your decision.

There is a very good discussion of these issues at a post just a few down titled "help please with ventilation"

Thanks for the references to the post below -- yes, I read it prior to posting my question. While it gives some great information (that really should be posted under the forum facts section) it didn't give me a clear indication of what I should do.

Any other experts out there want to chime in? Is there a reason why maunfacturers don't post the sound ratings for their fans? That certainly would be helpful information....

Conventional wisdom says that most of the "noise" comes from the air flow through the vent pipes, not from the fan itself. Yes, remote may be a little quieter but it may not make that much a difference. Also, remote fans are much harder to service, particularly if they're on the roof. At this point I wouldn't second guess myself, I think the hood you bought will be fine.

We were posting at the same time - one reason that manufacturers don't post ratings is that there are too many variables involved - installation issues, including things like duct length, can have a much bigger impact that the fan itself.

Some DW manufacturers list sound ratings (probably under optimal conditions) and then people complain when the DWs aren't as quiet as they were expecting.

Thanks for the advice, everyone. After weighing everything carefully, I think I'm just going to try to stick with the Monogram hood. Hopefully it won't be so noisy that I can't live with it --- and if it is, well, I guess I'll just suck it up (no pun intended) and have a different hood installed with a remote blower.

Also, to be fair nc, I know there are those here who I consider to be very objective and they place much less emphasis on the noise reduction gained going remote. I have to reemphasize that my experience with internal was a remodel. I had to compromise on duct size from the minimum req' of 8 inches to 7 and I had 2 hard 90 degree turns to boot. Most have said that accounted for additional noise in my case.

I think you will be very happy! If this is your first experience with ventilation of this caliber, you will be more amazed by the sheer volume of fumes and cooking output readily wisked away by the power of the unit and less focused on noise.

Also, I looked at your unit when you first posed your question and it is quite the attractive unit.

I'm installing a 1400 CFM remote blower, the roof is only about 4' from the top of the hood. Is there anything we can do from the installation side to help quiet things down?

How is the duct running to the roof? Is it through a chimney or chase in the kitchen? Or is it through an unfinished attic space? If the former, breezy2 had previously posted ideas about running a chase to allow a longer duct run: hopefully he'll add his (her?) 2 cents worth.

If the latter, you might have enough space for the Fantech LD10 silencer (it's 42'' long and 18'' in diameter) which should help.

Having used this type of exhausting venting system many times it is important to note the longer the duct run the lower the CFM performance. In one instance we had to add an extra "in-line"/"in-duct" fan extractor to keep the CFM's at the level necessary at the input or vent hood. Just FYI - Also you can up size the ducting and/or convert from round to rectangular ducting if the spaces you are running through require such, you just need to make sure you keep the cubic inch interior volume of whatever duct you are using equal to or greater than manufacture requirements . . .

Coming in to this thread a few years late but hoping there are still experts who can help. Wife and I are remodeling kitchen and planning a 42-inch hood with 900 CFMs over our 36” six-burner oven with 90k BTUs. Was planning to go with a Best unit that has an external blower mounted on the side of our house but the sales rep told me that it won’t be quieter because the hood will sit on an external wall and vent directly outside with minimal distance and you need at least 15’ to the blower to have any meaningful noise reduction. Do we think that’s accurate?

Please see my response to you at https://www.houzz.com/discussions/2305885/help-please-with-ventilation#n=92. In general, duplicate questions lead to scattered responses, so should be abjured.