range hood power

8 years ago

I'm seeing range hood power from 300 cfm to 900 cfm and everything in between. Any thoughts? I've got a gas 30" range with double oven

Featured Answer

zneret

8 years ago

All depends on what kind of cooking you do, and how far (and how far up) the fan has to push out to vent. I would go with at least 600 cfm. My old house had a 600 cfm Ventahood that only had to push up 1-2' and then straight out a 90 degree turn (supposedly 5' equivalent for a total equivalent length of 6-7'). I could cook Cajun smoke food (think of heating a cast iron pan until it is white hot (seasoning and oils burnt off) and then putting on a piece of buttered meat) without any smoke in the house, or setting off the kitchen smoke detector.

In my new house and new install, pretty similar but newer unit has to push up 2', go around a less than 90 degree angle. go another 3' and then a 90 degree or ~ 13'.

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Comments (6)

friedajune
8 years ago
last modified: 8 years ago
Yes to the above, but also there are other considerations, like the diameter of your duct from the hood to the outside. A 900 cfm hood will need either a 8" or 10" diameter duct. If your duct is e.g., 6" diameter it could handle no more than 400 cfms. What do you have, or, are you installing new ductwork? If the duct is too small for the amount of cfms, you will get more noise and less efficiency through no fault of the hood.

Another consideration is make-up air. When a hood has a lot of cfms, you run the risk of backdrafting CO into your house with the pull of the kitchen exhaust, rather than have CO exit the home as it normally would. This is a very serious matter. But it also depends on how tight your home is, your climate, and how strict your local Code is about makeup air (hint: they're getting stricter, not easier). A makeup air system can get very expensive. Usually you can get away without makeup air with at most 600 cfms, but if your home is tight, then no more than 300 or 400. Check with your local Building Code.
morphoto thanked friedajune
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barryv_gw
8 years ago
Morphoto, I can't give you much help, other than the say that if you want to know how much power a hood has, CFM may not be of much help. It is sort of like saying a car will get 35 miles to the gallon when driven 1 mile. Is the mile up hill, down hill, is the car loaded, is there a head wind or tail wind. CFM varies with different static pressure - and most don't tell you the SP that applies to the CFM they publish. When I was looking, I decided that a better way of looking at it was trying to find out the wattage of the fan motors- that may be hard to find as well, but to me it was less able to be manipulated by the manufacturers. BTW, I got clued into that when I bought a hood that was rated with a very high CFM, and when I got it , it had virtually no suction, and I checked , and the fan motors were very low wattage, meaning they had no pull if there was any restriction in the baffles or the venting.
opaone
8 years ago
Some info here: https://www.gardenweb.com/discussions/5161173/hood-faq
DrB477
8 years ago
The residential code most of the US follows requires makeup air with a hood of more than 400 CFM (whether you actually need it or not). Local enforcement of code is variable from strict to nonexistent.
User
8 years ago
Use a 36" hood over your 30" range.