'perfect' hood compromise

15 years ago

I've spent the better part of today reading your sage advice about island hoods and shopping for same. It ain't easy.

If I compile the recommendations, I come up with:

*baffle filter

*wider ducting (>6) to reduce noise

*a higher cfm blower run at lower speed is quieter than a medium run at medium speed to achieve same ventilation

*low sones

*trapezoidal shape to capture better

*cfm rated to max usage

Our install will be

*island over 30" induction range

*horizontal outlet

*new construction

*will not have a glass element in the hood (too much maintenance to keep it looking good)

*need about 600cfm

*200 miles from nearest city with a high-end appliance store (although Sears is 50miles away)

*in a great room that will be our main living space

*in home of a partially hearing impaired person, for whom background noise is very difficult

Would like to spend less than $3K. The rest of my appliance package adds to $7500 right now.

FWIW, I like the looks of the kitchenaid architect 36" KXI4336YSS and it's certainly in the price range. Absolutely no sones data anywhere (did find "690 mÃ¯Â¿Â½/h extraction rate at noise level of 65 db" at appliancist.com). Baffle filters, but 6" ducts.

Or the DHI361 Dacor 36" Millennia Island Hood, which has 8" ducts? Can't find a noise rating for it.

Or the Kobe IS2336SQ Kobe 36" Island Hood which has 6" ducts and low sones?

If I have to give up something from the list of recommended specs, which will I least regret? I don't care about brand names, matching appliances, so long as it works reliably and quietly.

If I pick a 6" vented hood, should I ask for 8 or 10" venting for a future replacement? SIPS construction, not sure what the cost differential would be.

Thanks for all the posts, they were very helpful.

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Comments (4)

wallycat
15 years ago
I was just reading the insert from the Seattle Times and it talked about how overpriced vent hoods are.
The guy has a blog and he picked a Zephyr island hood. It is available for under 1K at AJmadison site.
His was an island hood, which is what I may have to get, so it peaked my interest.
Frankly, I don't know much about hoods...I lived 50+ years without using a vent anything.
colin3
15 years ago
Since this is new construction, can you use a remote blower, and perhaps a silencer? See the illustrations on the linked Fantech page. If your aim is quiet, getting the fan far from the kitchen should probably be the priority.

Then you just need a canopy with baffle filters, 8" duct, and whatever lights and aesthetics please you.

Searching will yield pretty thorough discussion of the silencers and blowers.

Here is a link that might be useful: fantech
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davidro1
15 years ago
ditto, remote (inline or external).

then, the "trapezoidal shape to capture better" is empty and holds more cooking fumes.
kaseki
15 years ago
The larger ducting recommendations are to lower pressure loss and hence increase flow rate for a given blower. The velocity in the ducting will be lower with a larger diameter, thereby reducing noise. Depending on whether the ducting is generally warm, or cold, to minimize grease deposits the diameter should enable the velocity in the ducting to be around 500 ft/min (at full power) to 1500 ft/min for warm and cold ducting, respectively.

The trapezoidal shape not only provides a zone for transition from capture to containment, but also can direct the rising effluent to the duct with minimal "reflections" in the wrong direction and with low pressure loss.

Whatever actual flow rate you think you need given your cooking style should be increased when specifying the blower due to pressure losses in the system. A factor of 1.5 should be in the ball park. And what you think you need should account for the nature of the hood. An island hood is open on four sides so it is easier for rising effluent to escape.

Don't forget that to get air out of the house, one has to allow air back in. For low flow rates, this make up air (MUA) is generally obtained via building leakage. At higher rates, one has to use open windows or a dedicated passive or active, conditioned or not, make-up air system.

Furnaces, water heaters, dryers, and other combustion devices can back-flow their exhaust if the pressure in the house becomes too negative. And too negative can in some cases be as small as -0.02 inches of water column. I know experimentally that at -0.065 inches I could back-flow my oil-fired furnace and set off a near-by smoke alarm. I did not determine the threshold pressure for this; it was likely lower. I have since added a separate MUA for the furnace.

kas