weissman: we've batted this around before. It's obviously an issue of what each of us considers acceptable, but it was our experience at the lake house with a 600 cfm VAH hood over a 5 burner PGM365 Dacor cooktop that pushed me to spec a 1200 cfm Fantech remote blower and a 64'' Modern Aire hood liner over the new Lacanche in our home kitchen renovation. If I sear hard over the 15,000 BTU burner on the Dacor (i.e. preheat pan for 5 minutes over maximum heat and then dump in meat or fish) I get smoke that temporarily overwhelms the VAH blower and spills into the kitchen. Since that's kind of how I like to cook, it was an issue for me. So, for me 600 cfm (or, per the VAH hype, "equivalent to 900 cfm with a conventional blower"--which I don't buy) was inadequate for even one burner when doing this kind of cooking. I'm hoping the 1200 cfm will be more effective (though now I have fan envy, as there is someone who has recently posted about his 2500 cfm blower--now there's a reason for makeup air!). yoyoma: Re the continuously variable speed control--it's an option I'd consider a must if you're spending this kind of money on a vent hood. Again, this is based on my experience with our VAH, which also has a 3-speed control. The main thing a continuously variable control gives me is the option to run at a very low cfm setting, say if I'm just cooking one pot of rice. The VAH is just so darn loud even at low that I wish I could run it slower. The sound issue is also obviously why I went with a remote attic-mounted fan and the Fantech LD10 silencer. The silencer is a popular option as I know of several installations where the LD10 was used even when the blower was from a different manufacturer. For example, one appliance dealer quoted me a Wolf hood system but with the Fantech silencer. Do beware of the good point paddy 99 makes. I know that I'm going to get significantly less than 1200 cfm given a 20' duct run and the silencer, as well as one 90 degree turn. I did consider going even higher but at least with Fantech blowers it would have necessitated going to an even larger duct size which I did not have the room to use. BTW, I assume you're aware that it's important to use the largest ducting possible, typically 10'' size. And, as for yoyoma's choice of the Independent liner--it is by all reports a very high quality unit. My only issues with it revolves around the limited number of blower options. Their website makes it sound like you have to use their blowers. That makes sense with an in-hood unit, but I'm not sure that's really true if you're using a remote blower, which I think is the superior option. My guess is that you could use other remote blowers without problems, which would allow you to 1) use a fan with a continuously variable speed control and 2) choose an attic-mounted fan rather than a roof-mounted unit, which is what I think the Independent CFMR1400 that they sell appears to be. Issues with roof mounts are: 1) difficulty in installing (particularly with a multistory house and/or a steeply pitched roof) 2) Potential risk of roof leaks once you punch through it with the ductwork 3) Wear and tear to the fan due to 24/7 exposure to the elements on the roof versus in a protected attic. Well, that's all I know about hoods. Hope it helps.

The OP wrote: "- We can have a 10" duct, but can not install external blower because there will be at least 3 ninety degree turns for the duct to go through the roof (kitchen is on the 2nd floor and there is another floor sitting above the kitchen)." I must have missed this thread. Just what effect is being assumed here such that the location of the blower is affected by the three 90-degree bends, so long as none are right at the blower. (Hint: Pressure loss capabilities of kitchen hood system blowers are minute factions of an atmosphere. Due to this, pressure losses on the blower intake side and pressure losses on the blower output side have the same effect, particularly when a 10-inch duct is to be used for a sub 1000 CFM requirement.) If one wants [relative] quiet in an open area. the blower should be remote from the hood and a silencer placed in the intermediate ducting. As widely noted here over the past decade or so, rated CFM and actual CFM differ by a significant factor, and one cannot address kitchen ventilation with only hood system parameters. The make-up air system parameters are equally important.

As a first approximation, the CFM calculation is based on the flow rate at the entry aperture of your hood. And that directly depends on the area of that aperture. Your hood should be designed so that it captures the entire expanding plume that rises from the cooking surface. That generally means an overhang of about 3" on each side. For a 36" range, that typically leaves you with a 42" x 24" hood (or preferably 42" x 27"). You want air velocity of 90ft/min to get a hood that actually keeps up with your cooking (largely independent of the number of burners used concurrently). For the estimated aperture size of 7 sqft, you would need an extraction rate of 630 CFM. Unfortunately, the spec plate of your hood gives you the maximum flow rate without accounting for any losses from ducts and make up air. These loses can be quite substantial. They are a little hard to predict precisely, but a good rule of thumb would be adding 50% to make up for losses. That would be fine as long as you don't have very long ducts, lots of bends, or duct diameters below 8" Applying this correction factor gets you to needing about nominal 950 CFM for a 36" range. And yes, you will need an active MUA system with its own blower. Go any lower than that and your vent hood won't be able to keep up with your cooking. Going higher can be necessary if cooking foods with very bursty smoke development (e.g. wok cooking). A large capture volume for the hood can help contain some of these bursts and is generally a good idea anyway. But at some point extra flow also helps. We have a 1200 CFM blower over our 30" range and it does a great job eliminating all cooking smells. Often, I can turn it down, but there absolutely are meals when I need the full CFM.

I had a Blue Star - don't remember the kind but bottom of their lines. I really liked it. I'm a messy cook too and when food boils over or splats it just goes inside the stove on to a tray that you pull out and hose down in the sink. I like that feature a lot. It was also a piece of cake to pull the star shaped burner off and clean it on the counter or sink. (Though frankly my cleaning person did most of that work.) I loved that there was nothing digital at all on it. When I had a problem during Covid lockdown I followed a youtube video, took a few things apart, and repaired it myself. I'm completely not handy at all and it was a really easy.