1. Probably not much difference. Indeed, you need to check the specs on your installation, as there is typically a minimum length of ductwork needed if you are going to utilize an external blower. If the distance from hood exhaust to external blower is only a few inches, that may not work. Such a short run of duct really negates many of the advantages of an external blower.

2. More is better. You can always throttle the blower back with a speed control, but you can never run it faster than it's rated. And FWIW, we have a 600 cfm hood over a modest Dacor cooktop at our lake house and there are definitely times I find it wanting.

3. In general, more is again better. Our main home hood is 64'' over a 55'' range and the extra capture area is definitely a plus.

1. I defer to Clinresga

2. Go big, especially if you get a deal. My CC 36" 6 burner rangetop has a 600cfm Rangecraft hood above. I found a great deal on the custom curvy hood with the pre-installed blower, which I could never have afforded otherwise. Sometimes I wish I had gone for a bigger motor rather than the small one I was stuck with when I bought mine. I am happy with my decision overall.

3. My hood is 42", and the proportion over the rangetop seems right to me. A larger hood could possibly look a tad out of scale depending on the rest of your kitchen layout. Will the hood be between uppers on both sides? Between windows? Can you mock up a large hood in your kitchen or on an empty wall someplace? Mock ups helped me tremendously when making decisions throughout our whole house reno.

Agreed with the rest. I wouldn't worry too much about the width if you're doing a custom kitchen design. You can make up for any discontinuity. Or if you want to offset the difference, you can make a counter space under the hood for a small appliance.

As to the external blower, I was told specifically that not only don't they work well in through the wall installations, but that they can be louder that way too. I don't know if this is accurate, but was told by someone in the industry.

Thanks, everyone. This hood will be mounted between two windows (about 60" apart). Can't do a mock up yet, as there is currently a wall in between those windows that we are planning to demolish. I appreciate the confirmation about external blowers.

A follow up question: It's my understanding that the central components of a range hood are:
1. Blower - does the work (i.e., sucks the air).
2. Duct - channels the warm air outside.
3. Liner (with baffle) - helps separate the grease from the air.
4. Cover (what do you actually call this?) - makes the whole thing look pretty. Made of steel, copper, or wood.

If my assumption is correct, is it possible to purchase items 1-3 and then have a carpenter create a custom cover? Or is there something about a hood cover that requires a specific manufacturing process?

You can assemble your own pieces, but you can also buy the whole "guts" as a unit minus No. 4. Theoretically, if you did that, the engineers would have already figured out the angles and distances and all that functional stuff. The guts are also called "liners" (confusing, as sometimes the frame that holds the filters is called a liner), or insert, among other names.

I have a 40 inch dome shaped hood over a 30 inch range. It needed to be at least this big to fit the 1200CFM unit into it, given it's dome shape (or so I was told). At first I thought it looked too big over the range but now I think it looks just right. The shape has a lot to do with whether it will look right. A barrel that is 48 at the top and 48 at the bottom in width is going to look more massive than a dome which is 48 at the bottom but narrows at the top.

Thanks! It's all starting to make sense to me now. I was confused by the "liner" terminology.

Did you ever install this combo? I have a 36' wolf rangetop and found a steal on a 48' hood. Was just wondering how it would look.

Thanks

Note that as the hood gets larger, so does the cfm requirement, even though the range/stove underneath is the same. The reason is that the velocity of air through the baffles needs to be in the ballpark of that of the uprising and expanding effluent for good containment.

Proportionately more cfm through a larger hood will generate the same baffle noise per square foot of baffles, but overall the total sound level will be higher. This baffle noise is not particularly intrusive, though, so it shouldn't be a large concern.

On the other hand, a nearby larger fan could be noisier if it is designed to move air with small high velocity blades instead of large low velocity blades. If part of the hood, the combination should be audited for noise.

For a lot of cooking, adequate capture and containment is achieved at lower fan settings, so noise from suitable components should be below conversation level at reduced power. At high fan power, there will be a difference in the noise with a roof-mounted fan and intermediate silencer versus an in-hood fan.

kas