how high/big should kitchen exhaust hood ductork be

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  #1  
Old 07-31-10, 05:48 PM
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how high/big should kitchen exhaust hood ductork be

I am having a duct put in for a range hood. I plan on redoing the kitchen in the next year or two, but am installing the ductwork for the hood now. (i am putting on an addition and it makes more sense to do it at that time. It will have to be vented up to the roof since the addition will be abutting the kitchen.)

I was wondering if there is a standard height for the ductwork?

my stove it 36inches height. 8ft ceiling (actually 95 1/4in to be precise I plan on having the bottom of the hood about 30inches from the cook top, give or take a few inches. This will of course depend on the height of the hood itself.

The main issue is, I don't want to have it at a height which will cause problems if/when I ever wish to install new kithing cabinets! ie hard time finding cabinets that would accommodate a hood at the height the duct is on the wall.
When the time comes for replacing the cabinets, we are planning on the ones that go all the way to the ceiling.

thanks.

PS, If there is a more appropriate part of the forum for this question, just let me know.
 

Last edited by newhomeshopper; 07-31-10 at 06:14 PM. Reason: spelling
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  #2  
Old 07-31-10, 07:25 PM
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It's hard to speculate, but I would use rectangular ducting. I used it in a previous house. It ran up the inside of the cabinet. Most range hoods will handle the rectangular and you can then transition to round when you get into the attic. as to size, check a few hoods . I'm thinking 4" round, but check it out.
 
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Old 08-01-10, 12:23 AM
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Four inch round duct is way too small for a kitchen range hood. I would use nothing less than seven inch round or 3-1/4 by 10 inch rectangular. This would be for a relatively small hood rated at 250 cubic feet per minute or less. For a decent sized hood (300 cfm or larger) I would use even larger duct.

The fool that installed my kitchen range hood used four-inch and terminated it out a sidewall with a clothes dryer terminal. It is just slightly better than useless.
 
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Old 08-03-10, 06:07 AM
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how high off the floor should I install the hood?
 
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Old 08-03-10, 07:38 PM
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18" - 24" above the cook top surface to the bottom edge of the hood. Furd's right on the duct size - it's been many years since I installed one.
 
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Old 08-09-10, 02:41 PM
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If you haven't yet chosen a fan, you can only guess. If you're going straight through the roof, set up your framing so that it will accommodate the maximum duct size you will use.

If you just want a garden-variety fan/hood combo, the 3-1/4x10 or 8" round would be fine in most cases.

However if you want a second-to-none install with a price to match, you might want a separate hood with lights and baffles only, a silencer, and a roof or inline mount fan. Fantech has them up to 2000 CFM at 0" WC. That would require a 12" round pipe.

The main advantage to the remote fan is it is far quieter than a fan/hood combo, so you can cook and entertain at the same time.

A second advantage is that you are pulling air from the kitchen instead of pushing, so you don't have to worry about blowing cooking odors out through duct seams before the air gets to the roof cap.

A third advantage is that you can locate an additional grille on the exhaust duct at the kitchen ceiling to help get out odors that might evade the hood and rise to the ceiling, such as what might escape from the broiler, from a microwave oven, from the trash can, or from the rotting leftovers in the fridge.

Of course you'll want to think about make-up air too if you're running a larger fan!

Here's a link to Fantech. Their site often runs very slow:
Inline Exhaust Fans | Fantech Residential
 
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Old 10-30-10, 02:41 PM
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The exhaust fan I plan on buying asks for a 3 1/4 x 8, but what i was thinking is installing the largest recommended for non-commercial fans.
what would that size be?

The thought here is that it would be relatively easy to put an adapter if I for a fan that requires a smaller duct, as apposed to the work to enlarge currenct ductwork that I may need for another fan in the future.

I'm also guessing that the narrower the ductwork, the louder the exhaust will sound when it on. Am I wrong?

Thanks.
 
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Old 10-31-10, 07:52 AM
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When you increase size you reduce velocity and turbulence. I can't tell you the effect in your situation, but I would guess lower velocity air would be less likely to push out grease, other particulates, and water vapor, so I would ask questions about accumulation and condensation.
 
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