What island hood should I get?
I have a 30 inch induction cooktop and a 15*20 inch electric grill on a peninsula. The peninsula separates the kitchen from the family room – no wall on that side.
We use the grill a lot for chicken, fish, and steak, so it’s important to have a good vent system. We have a 48 inch downdraft with an 8 inch blower, and it is totally inadequate (the installation is correct with no turns, solid vent piping, and a short run to the outside). The vent/blower is rated for a max of 600 cfm’s. Even with the help of a small room fan to direct the smoke, the downdraft can’t suck out the smoky air when grilling steak. When we test the downdraft, it sucks air from only about 5 inches or so away (not good when the grill is 20 inches long).
Bottom line: the down draft simply can’t do the job for the grill. After a lot researching, looks like our best bet is to buy an island hood. Our primary purpose is to vent the grill – the cooktop really doesn’t create much smoke. Island hoods come in many sizes, with varying CFM levels, and duct diameters.
Questions:
If two hoods have 900 CFMs, but one is 36 inches, and the other 30 inches, will we get better exhausting from the smaller hood? 30 inches will still be wider than the 15 inch grill. It’s OK not to have much of the hood over the cooktop.
Does it make any difference if we have a flat glass or curved glass for the hood?
Is a 600 CFM 42 inch hood with an 8 inch duct better (meaning will exhaust more smoke/air) that a 500, 600, or 900 CFM smaller hood with a six inch duct?
We want an island hood with the best exhaust capabilities, and can’t figure out what combination of hood size (30, 36, 42, or 48 inches), CFM, or duct diameter.
I hope someone can help us!
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Replies
Willa,
I'll let other readers answer your questions about the best type of 900 cfm range hood. I just want to warn you that 900 cfm range hood fans can cause backdrafting problems. In most homes, such a powerful fan will require the installation of a makeup air system.
For more information on this issue, see Makeup Air for Range Hoods.
I know the 48 inch downdraft with a potential 600 CFMs is inadequate to vent our 15*20 grill with only two steaks on it. How many CFMs, then, do I need for a hooded vent? Will 600 CFMs be adequate? We live in Southern California, so our windows are generally open year round. I don't know if backdrafting will be a problem or not. I wasn't planning on a makeup air system. To make things worse, I can't seem to find anyone who is knowledgeable to answer the questions (except on board like this one). Thanks for your advice! More is appreciated...
Downdraft ventilation is utterly useless, and shouldn't be a basis for comparison. Your discovery that you can't suck air from very far away is why downdrafts don't work. In residential duct design, return ducts generally pull air from ~ one duct diameter from the register. Effective kitchen ventilation is first about hood placement, and second about cfm. At the risk of repeating myself, at the end of Happy Birthday no one asks you to suck out the candles.
HVI writes standards for kitchen ventilation. In my view, they over-ventilate, and folks should generally target the minimum end of their proposed range. Regardless, for a 30" cooktop not against a wall their highest rate is 375 cfm. Their minimum, is 125 cfm.
http://hvi.org/publications/pdfs/HVIRangeHood_4Feb08.pdf
I would do this via a remote fan from Fantech - either wall or roof:
http://host0158.csmhosting.com/Catalog/sheets/p27.pdf
If you go with a cabinet-style hood (strongly recommended), then couple a FanTech fan with the cabinet manufacturer recommended liner, or at least verify compatibility of the hood liner with the cabinet (trust me). Use FanTech's butterfly damper and add a duct silencer if you go over 200 cfm.
Larger duct diameter per cfm are probably indicative of greater manufacturer honesty. It's really unlikely that a 6" duct on a range hood is getting anywhere close to 500 cfm, let alone 900. Big hoods close to the action are better. I follow JLC Field Guide for hood placement, and couldn't readily find something online, but I'm sure NKBA has the same standards if you could find them.
Here's a decent powerpoint from a recent Build America conference:
http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/cq7_kitchen_ventilation_singer.pdf
Thanks for your responses, they've been very helpful. Here's my plan thus far - what do you think?
The downdraft is working fine for the cooktop, so I've decided not to deinstall it.
I am planning to get a 30 inch chimney island hood for the grill, which is 15*20 inches. Most of the 30 inch island hoods I've looked at are at least 20 inches deep, so the hood will extend beyond the width of the grill and will be about the same size as the depth of the grill, maybe an inch or so larger. The hoods range in CFMs from 400 to 900. Do you think a 400 CFM will be able to handle smoke from grilling steaks?
A true 400 cfm hood will definitely be adequate for grilling steaks. A true 200 cfm hood will be enough for grilling steaks. However, if you're leaving the downdraft in place and adding 400 cfm, a shrewd code official could call for make-up air based on the total ventilation system exceeding 400 cfm. Either way, I'd recommend checking for hot water and furnace spillage with all ventilation systems running and the air handler both on and off.