Range hoods: capture vs. containment?

2 years ago

last modified: 2 years ago

I have been researching as much as I can on this forum about range hoods (thanks especially to @kaseki and @opaone for their excellent posts and FAQ) and have settled on doing a custom hood with an external blower and silencer. My great room and kitchen are being gut renovated, so I have a decent amount of leeway on rearranging internals in the wall and making a new roof penetration. The ceilings are about 10.25' high, with a 30" attic above that + some space for the ceiling joists. I'm going to have a 36" Thermador Freedom induction cooktop on 24" deep countertops with the oven under it. The hood is currently designed to be about 6' from the ground (36" high countertops, 36" from countertop to hood), though this is adjustable. But with those specs, this gives me about 8' from the bottom of the hood to the roof.

Here is a an older draft elevation for the kitchen wall with the hood (ignore the part where it has an S.S. chimney hood -- that's just a fill-in):

Our kitchen is being planned with all open shelving so I'm pretty keen on getting a hood that performs well enough to keep my shelves as grease-free as possible while being as quiet as possible (the kitchen has an open floor plan so I don't want turning the hood on to stop all conversation!). It also means I have no cabinetry to blend the hood into.

I'm currently leaning towards a 42" wide x 27" deep hood, but as I've been trying to actually find a hood I've had a few questions that I'm curious if anyone in this extremely helpful forum knows the answers to:

Most hoods and hood liners give you the external dimensions of the hood, but am I right in thinking that for capture, the more important dimensions are the dimensions of the actual opening of the hood (so the external dimensions minus any light bar, trim, etc.)?
I love the high capacity hood liner from Prestige because of its increased containment volume compared to most residential hoods, but it is only 21.5" deep externally. Does anyone know what the actual aperture of it is if you exclude the trim?
On the other hand, I'm attracted to the idea of just making a custom hood from Modernaire, Rangecraft, Coppersmith, or Havens (I'm also open to other suggestions of custom hood makers -- it's something I've only recently started looking into). With a custom hood, I could create a 27" deep hood with a larger aperture. Modernaire let me know that on their standard liner, the light bar (5.25") + trim (2") + flange (1") is 8.25". So on a 27" custom hood, I should get a 18.75" deep aperture, which beats the Prestige hood liner. For performance in removing effluent, is it better to have a larger capture area (which I believe the custom hood could get me) or a larger containment volume (which I believe the Prestige high capacity liner would get me)? I would instinctually believe capture, but curious if the real engineers here know better!
I have seen tons of glowing reviews here about Modernaire (and the brand performed well noise-wise on @kaseki and @opaone's noise charts), but does anyone have experience with Prestige, Rangecraft, Coppersmith, or Havens Metal hoods?
If the blower is external and the duct is a straight shot with a silencer, how much does the hood itself matter for noise? And on that note, does anyone have experience with Prestige High Capacity hood liners, Rangecraft, Coppersmith, or Havens Metal hoods and know how loud they are? My primary concerns are performance and noise followed by aesthetics.
Can you create more mechanical containment in a custom hood by simply installing the baffles at a higher angle or higher up inside the hood?

Know that's a lot, but I appreciate any insight on any of these questions! Thanks!

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Comments (4)

kaseki
2 years ago
Looking forward to answering your questions later today.
tassadar thanked kaseki
kaseki
2 years ago
1) Short answer is "yes." A small distance outside of the clear aperture may also be effective. In the case of my Wolf Pro Island hood, I count the inch at each end and back, but not the higher curved part that adds to the specified dimensions. I count an inch of the light bar zone also, which is significantly larger. This is really in the noise, though, given the ability to estimate baffle pressure loss, among other things.

2) Not me.

3) It doesn't help if containment is perfect (which is our goal) if some of the effluent plume is not captured. To the extent feasible, determine the contour of the largest pans you might use on all your burners. Determine your hood height above the pan bases and multiply by the tangent of 10 degrees. (This is the minimum; somewhat larger angles can be argued for in various circumstances.) Extend the outside edge of the pan contour all around by this height x tangent value. Your hood capture area should encompass this larger area. In your case, the back is a wall and the hood need not go any farther.

Larger containment volumes (significantly larger than residential hoods provide) allow averaging of the highest velocity plumes over the baffle space allowing commercial hoods to get away with somewhat lower CFM for a given capture aperture area.

4) @opaone's noise charts. I don't have an iphone to use to contribute values with.

If you use an external or in-line but distant blower, and install a silencer such as Fantech makes in the path from hood to blower, the blower blade tip noise and upper duct turbulence noise will be significantly reduced. My roof-mounted Wolf/Broan 1500 CFM rated (at zero static pressure) blower pulling an actual ~ 100 ft/min across my hood capture aperture is fairly well attenuated such that the dominant kitchen noise in the voice band is baffle hiss. This might vary with baffle design.

5) I can't answer specifically, but with my hood blower on full power one can converse at normal talking level with someone on the other side of the hood or a few feet away. From the cook's point of view, Intelligibility of a TV in the open room on the other side of the peninsula requires a modest volume level increase over listening with no blower flow.

In my opinion, find a hood that best solves your optimization of the trade space of capture, aesthetics, cost and use an appropriate remote blower with a silencer, and you will find the noise is attenuated enough. If you follow the general "prescription" of @opaone's commercial setup, you may be able to run lower flow rates from a large enough blower that the noise is negligible for most cooking tasks. Opaone has discoursed on this in a number of threads that should be reviewed.

6) The more the hood design approaches a commercial configuration, the more volume below the baffles you will have. See this thread for a relatively practical quasi-commercial solution.

https://www.houzz.com/discussions/6204496/range-hood-questions#n=8
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tassadar
Original Author
2 years ago
Thanks a lot for the detailed reply, @kaseki, much appreciated! Will definitely look a further into doing a commercial setup (I had assumed commercial setups would cost a lot more than a custom hood, but from that thread it seems like the cost was comparable).

Had one quick follow-up if you have time: I saw in a separate thread that you had mentioned that you believe the performance trade offs of a chimney-style hood are not worth it (I imagine something like https://www.pinterest.com/pin/65020788347340134/). Why is there a performance trade off for a chimney-style hood like that as long as the chimney itself is large enough to be comparable to a 10" diameter duct?

Thanks!
kaseki
2 years ago
Trades are only relevant in context of all the aspects being traded. I have no objection to hoods of that general configuration, so long as they are sufficiently large in capture area, have baffle filters unless there is some overriding reason for mesh filters, and have sufficient flow rate for containment. My Wolf Pro Island hood is effectively of that type, only much larger. Generally, useful residential hoods are commercial hood configurations that have been figuratively mashed into smaller volumes and prettied up to the point where the relationship is hard to discern by the casual observer.

Please link the thread so I can divine why I wrote whatever I wrote.

Range hoods: capture vs. containment?

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Range hoods: capture vs. containment?

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