choosing a ventilation hood

19 years ago

I see that there are a few vent hood questions already on the top of the list, and I guess I'd like to add a couple more.

I have a 30" Bosch dual fuel range, with a total BTU output of about 46K, so I know I need something that can move 460 CFM+.

My first question deals with ducting:

There is a hole on my roof with a jack now, but if I use that opening, it will add 9-12 feet and at least two 90deg bends to the ducting length. I guess my options are: 1) put in a new hole and jack, or 2) make sure that whatever hood I buy can handle that added distance. A new jack installation should cost about $500-600, so it seems to make more sense to spend money there, and have a nice short, efficient, QUIET duct length rather than to keep the old hole and have to spend more on a stronger (louder) hood.

I hear that there are formulas to calculate the "loss" of CFMs due to distance and angles, but I cannot find them. I dont know if adding 12 feet and 2 bends cuts down efficiency by 20% or 90%, so I'm having trouble deciding what to do.

My second question deals with baffle/filter differences:

As I understand it, baffles are quieter and more efficient at high flow rates, and mesh filters are better at low flow.....sort of correct? I have been told that baffles have no place in a residential kitchen, and that they are popular only because they look professional, but I have also been told that mesh filters are noisier and more difficult to clean, and dont last as long.

We boil a lot of pasta and do stir fry, but not a lot of heavy frying and there is no grill. I guess I want whichever option is best for "moderate" use, and being quiet is very important to me, but not if it means sacrificing a lot of eficiency. Which sounds better in this context- baffle or mesh?

thanks,thanks,thanks!!!

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Comments (3)

weissman
19 years ago
I can try to answer some of your questions. Baffles are far superior to mesh filters and easier to clean. Who told you not to use them in the home? Ventahood doesn't have either - they have squirrel cages - some people find them easy to clean, some don't.

Do you currently have ducting or just a hole in the roof? Different hoods require different size ducts - 6", 8" or 10". Get ducting to match your hood or a hood to match your existing ducting.

600 CFM, a fairly standard size hood will more than meet your needs. If you have existing ducting then I would recommend using it - even if you have to increase the length and add some elbows. If not, then a shorter run with fewer bends is desirable.
muscat
Original Author
19 years ago
Thanks weissman!

What I have now is an 8" hole in the ceiling vented to the roof jack with an electric bathroom fan in the ceiling. Weird, I know. The jack on the roof seems to be in fine shape, but I'm sure that the ducting in the crawl space needs replacing no matter what. The new range and hood will be on a different wall- the drawing below shows the hole (circle with and X) and the new range location. It is about an 8' distance straight across, or 4' along one wall and 7' along the other.

{{gwi:1454999}}

Given those distances- might I be ok using the old hole? The hoods I'm looking at go from 300-750CFM. I dont want to always have to use high power, though.

I wasn't told NOT to use baffles in a home, just that they did not work as well as mesh filters at lower power, but he was vague as to what is "low" and "high" power....so I was not convinced. I have mostly been considering Kobe hoods, as they seem pretty quiet, and they have hoods in all three types- mesh, baffle, and impeller fan type with grease cups, and are under $1K.
thanks!!!
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lascatx
19 years ago
I have 3 feet of duct from the hood to the ceiling and another 12 feet or so to the rof. I have one 90 degree turn and one 45 degree turn. I did go with a 10" duct because of the turn , hopoing not to restrict airflow and increase the sound. I don't remember the formula for the turns, but they didn't change the cfm requirement that much. I'd go with a 600cfm or maybe a 900 if you'll feel better about that and don't put another hole in the roof. Just better not to go punching more holes inthe roof in my book, and you're not talking about anything major here to change that.