IMHO, 600 CFMs is more than enough for a 30" range. Is your 6" duct already in? If not, I would consider putting in an 8" duct which will give you more flexibility. How deep is the hood - the deeper the better - capture area is just as important as CFM. Also, what is the requirement in your locale for make-up air? If you get too many CFMs you may have to put in a make-up air system. That's probably why they also offer the hood with a 400CFM option.

OK - I took a look at your link - the hood is only 20.6" deep, and has mesh filters. The price is very good but you ought to consider deeper hoods with baffles.

Thanks weissman.
I tried looking for a 600 cfm hoodfan with a greater depth, but found nothing.
Is there a hood you would recommend?
Also, could I get away with fewer CFMs?

I looked at the City bylaws, and apparently for new build, it is 280 cfms before you need to make up the air. But for older houses, it's on a case-by-case basis and there are no real rules or guidelines.

After searching local forums, one suggestion was as follows: "Open a window in the house, away from the fan, and tape it off with a sheet of plastic. Turn on the fans and see how the plastic gets sucked into the room. If its very dramatic, you may want to think about introducing fresh air into the system. If its a slow, lazy reaction, you might be ok."

I bought my hood years ago - it was a DCS hood with 600 CFMs but only 20" deep. With hindsight, I'd like a deeper hood. I'd take a look at Kobe hoods - they have many different models and sizes and generally get good reviews.

Weissman gave great advice. I would emphasize to avoid the mesh filters. They get clogged with grease and then block airflow so your exhaust won't be good no matter how many cfms you have. Unless you are willing to clean a mesh filter frequently, I recommend a hood with baffle filters instead. Of course baffle filters will need to be cleaned too, but they won't block air flow.

If you can enlarge your duct from 6" to 8" idiameter it will help with air flow and noise. If you can't, that's understandable, but you will get more noise, so don't blame the hood.

Also check out Costco's hoods. Their hood inventory is always changing, so keep checking in if you don't immediately see something you like. The hoods at Costco are a lot of bang for the buck, and Costco has a great return policy if need be.

Here is a link that might be useful: Hoods at Costco

With clean mesh filters and a six-inch duct and restricted MUA, the actual flow is likely to not exceed 400 cfm at best.

What is needed in my view is 90 cfm actual times the area of the hood aperture in square feet. The size of the room, nearby rooms and beams has nothing to do with capture and containment, the primary functional requirements of a hood. Room size and configuration does have to do with the time it takes to flush the rooms of odor and smoke if the hood is inadequate.

So if you obtained a 24-inch by 36-inch aperture hood (six square feet), the requirement would be for 540 cfm. This would typically require a 800 cfm rated blower. You may find less cfm to be adequate relative to past experience, or less cfm to be more cost-effective, as a 6-inch duct would be a tad tight for such a blower. Smaller hood apertures, while perhaps missing capture of some effluent, would require less cfm to function with the effluent that was intercepted as it moved upward to the hood.

Do not run the fireplace with this hood operating unless you install a source of MUA that keeps the house negative pressure smaller than about 0.03 inches of water. This will generally require a fan-augmented MUA system if the house is closed up, but an open window on the windward side will usually suffice to feed both hood and fireplace with little backdraft.

In the case of combustion appliances, however, you have a CO risk that has to be evaluated. Safety precludes depending on open windows. Either a separate MUA for the appliance is provided (such as the room the appliance is in is closed off and vented to pull air from the outside, or, in the case of furnaces, MUA ducts are installed), or the hood blower has to be linked to the MUA blower in some manner.

kas

Ok. There's an NXR with baffles and it is 24' deep which means good coverage over the range. It has a 7' duct.
800cfms (and I probably wont run it that high since the coverage over the range is good.

It is only $450. That seems like a good price.

What do you think?

Here is the link:

Here is a link that might be useful: my link

BTW: just because the blower might have a higher CFM rating doesn't mean you have to run it on high all the time. A 900cfm vent run on medium will be quieter than a 600cfm on high.

Hydrangea - I am interested in this topic of hoods. I looked at your link for the NXR hood. At first I thought it looked great. But then I was confused by the mention of the "squirrel cage motor". Does someone know if that is the same thing as the VAH/Ventahood "squirrel cage"? Cause I've read on this forum that people think the VAH squirrel cage is a pain to keep clean. But the VAH hoods don't also have baffles at the same time, so I am confused.

On the same link that the NXR hood is on, I see an Ancona Chef Undercabinet II hood with baffle filters. I wonder how that compares to the NXR hood--the cfms are different and it is 22" deep while the NXR is 24" deep. I am still in the planning stages, so I am not even sure whether I will have an undercabinet hood, or go for the "look" with the chimney hood (and the expense of all that tile). I am bookmarking this page though. Thanks.

Here is a link that might be useful: Ancona Chef Undercabinet Hood II at Costco

This post was edited by Sahmmy on Tue, Oct 28, 14 at 20:58

Sahmmy -
Wow, I did about 30 mins research on this topic. I don't think people are clearly expressing the differences between all the vent options. I've posted my findings in a new post.

VAH squirrel cage design blowers use the blower to impel grease particles onto the local blower surround instead of letting them pass by and condense on the ducting, where they could be a fire hazard. Hence they act as both a blower and a filter of sorts.

Baffle designs separate the filtering function from the air movement function. Baffles allow the blower to be roof or exterior wall mounted, thereby reducing noise, among other modest advantages.

My view, occasionally expressed here, is that the most efficient and effective hood designs are by necessity those used in commercial kitchens, which have a very high electricity bill due to ventilation needs. Residential hoods that emulate commercial designs are deemed to have some of their advantages, while usually providing tolerable aesthetics. It is of course always possible to made A look like B without B's benefits, so some care in selecting A is needed.

I believe hood systems made by reputable sources will all work as described. Unfortunately, the descriptions are never complete. I am certain that my Wolf 1500 cfm rated roof blower with Fantech in-line silencer is quieter under my Wolf Pro-Island baffled hood at fullpower than a similar rated flow rate VAH would be at full power in the same sized hood. Clinresga on these pages a few years ago reported measuring two similar hood systems, one VAH and one non-VAH in two houses he owned, and found the then VAH noisier. This is because fan blade tip turbulence noise dominates, and can be suppressed when the fan is roof mounted, but can't when the fan is in the hood. Once that is suppressed, then the next dominant noise is baffle noise, and at 90 cfm per square foot of aperture using reasonably designed baffles this is only a hiss lower in amplitude than a wok doing its thing.

kas

This post is very timely for me. We are in the midst of our kitchen remodel and upgrading to a 36" 6 burner gas range top from a 30" electric. We have been advised to increase the duct pipe to 10" from the current 6". It is a direct horizontal vent of 4 feet. We are prepared to do that - no problem.
I hope this is not too stupid a question: Who provides the duct piping? Does it come as part of the appliance package or does the owner have it in place before the appliance arrives?

thx!