I think it will depend a lot on what cooking you do. Boiling water? Shouldn't be a problem. Pan frying? Not enough unless you love the odors of greasy meals past.

400 CFM is actually good enough for your set up.

All these homes with 1000+ CFM hoods rarely ever use the high speeds and mostly use the 200 to 300 CFM speeds for most of their cooking.

Each cooktop and range will have minimum recommended specs. 400sfm should be fine. Many of the less expensive hoods have smaller numbers, even recirculate filtered air back into the room. The real issues come with large gas ranges, but confirm that with cooktop manufacturers specs.

Use a glass lid when frying so you don't need as much heat and don't create as much smoke/grease.

We have induction and 600 CFM and rarely run on high. Usually on low unless deep frying.

@Jakvis, @Jeffrey R. Grenz, General Contractor, where are you getting information to make your recommendations? What types of cooking does the OP do? How often? How sensitive to odors are they?

Thanks. I think I'm going for a 30 inch range with a 36 inch hood. We are mostly vegetarian but do cook curries. I'm looking into make-up air, and if it isn't prohitively expensive that would obviously be the ideal way to do things, but I'm on a limited budget so trying to tease out whether this is an area that I would truly regret it.

Some more info here: https://www.gardenweb.com/discussions/5161173/hood-faq

We eat a plant slant diet (mostly veggies & legumes, occasional meat (https://www.bluezones.com/recipes/)) so know where you're coming from. Curried veggies & beans is a favorite of mine. For us there's no way we'd plan for a 400 CFM hood for that. Love the taste, really despise the leftover odors. That's my personal preference though.

Keep in mind that a '400 CFM' hood may function at only 100-200 CFM depending on the blower, ducting, and how leaky your house is. Is this a new house or existing? Kitchen remodel? What is your tolerance for odors of meals past? Do you entertain much? If so, what is the tolerance for odors of your guests?

Hi opaone,

"where are you getting information to make your recommendations?"

Well I don't know about the others but I'm getting mine from 46 years in the appliance industry doing service and sales. In these 46 years I've been in roughly 50,000+ homes and probably talked to at least twice that many customers. I guess this would qualify me in most peoples minds to make recommendations.

By the way 200CFM in a 15'x15' kitchen with an 8 foot ceiling will have a complete change of air every 9 minutes. At 300 CFM it is 6 minutes. (15x15 is a little larger than most kitchens but you can see where I'm going.)

200 CFM with a large enough capture area at the correct height will pull all cooking effluent from the cooking area. If you go with a smaller capture area or higher than recommended height you will need higher CFM's.

@Jakvis, I was actually referring to knowing nothing about the size of the OP's cooktop nor the styles of cooking they do.

"200 CFM with a large enough capture area at the correct height will pull all cooking effluent from the cooking area."

All? Really?

"By the way 200CFM in a 15'x15' kitchen with an 8 foot ceiling will have a complete change of air every 9 minutes."

Complete? You are confusing equivalent volumes with changes of air. If the make up air is coming from a doorway adjacent to the hood then it could take 40-200 hours to effect a complete change of air. If 100% of the make up air is coming from the opposite side of the kitchen then you're looking at 1-3 hrs for a complete change depending on temp and humidity.

Worse, you're guessing on the size of the OP's kitchen and that it is enclosed. Even a small open floor plan house could have the kitchen in a corner or side of a 22'x30' room. And likely with at least a 9' ceiling though 10-11' is common as is vaulted.

But worse is how unimportant this is. In even your idealistic scenario any effluent that has not been immediately exhausted will have begun to spread throughout the house.

Thank you all for weighing in and asking probing questions. It is helping me think things through. The house was built in the 50s. If I open a window when running the hood, would that help ensure that it is running at 400 CFM? The ceiling is 8 ft (or maybe lower), and I plan on getting the hood installed as low as possible. Is the chimney shape more effective than an under cabinet ducted hood?

A few points.

If the room volume of air is expelled in T minutes, then in T minutes the odor and grease (not yet deposited) will have been diluted to 1/e of its initial level. The dilution is exponential. e = 2.718... Another 1/e dilution occurs in the next T minutes.

frazzlehead: Blowers are rated at zero static pressure -- hanging in free air. When attached to a hood, even with no ducting and open unscreened windows, there will be a pressure loss in the hood due to baffles or filter meshes, and due to abrupt transitions in the sheet metal. The pressure loss determines the blower's actual volumetric flow rate, and this is documented on the blower's "fan curve." Example fan curves may be found at Fantech's site and at Broan's site.

A hood's primary two functions are capture and containment. Capture requires that the hood overlap the rising and expanding cooking plumes from the pots and pans. (More precisely, it requires the hood to overlap the higher velocity plume components such that the wider angle lower velocity components are entrained into the hood air as it passes over the cooktop.)

Containment requires that the air velocity at the hood's filters and over various sheet metal parts on the cooktop side of the filters be high enough that when a plume portion strikes one of these components, the plume effluent continues to the filter and is pulled past the filter. The air velocity needed depends on the plume velocity and various other fluid dynamics details. For an induction cooktop performing high temperature cooking such as wokking or searing, the plume velocity is in the vicinity of 2 ft/s. The velocity in a baffle gap is probably twice the blower induced air velocity, so lets assume 1 ft/s is needed over the entire hood entry area.

For a 3 ft x 2 ft hood entry aperture (6 sq. ft.), 1 ft/s = 60 ft/min requiring 60 CFM/sq. ft. or 360 CFM actual flow. For lower temperature cooking, lower velocities should be sufficient.

For a hood, duct, screened open window configuration, I would want at least a 540 CFM rated blower. Less will work with more modest cooking. Note that even simmering bacon with a very low plume velocity requires some significant flow rate or else baffle filters will not perform centrifugal extraction of grease. In such is the limiting case, mesh filters may be better. In all other cases involving significant cooking temperatures and plume volumes, baffles are better.

The best hood configurations are commercial configurations, because maximization of performance for electrical cost dominates commercial kitchen ventilation trades. Residential hood configurations that carry over some aspects of commercial configurations are better than those that don't. However, for very low flow rate needs, it probably doesn't matter much whether chimney or under cabinet. Just be aware that a future home buyer may have a different cooking style, and may possibly appreciate his needed expense of upgrading.

In summary, better is the enemy of good enough, but good enough is the enemy of long term planning.

Can't thank you enough for weighing in here, and in all of the archives. I think I'm going to have to bite the bullet, plan for make up air, and buy a cheaper fridge.

For others reading this, if gas cooking, the requirement is around 90 CFM/sq. ft. Certain more restaurant like cooking activities can require even higher specific flow rates. See the Greenheck reference at: https://www.tagengineering.ca/wp-content/uploads/2015/02/KVSApplDesign_catalog.pdf

I have a 400 blower, for my induction, did not want to do make up air and wanted to be within code. It works really well, and was inexpensive. I didn’t read all the expert posts, but I do know that the length of the ducting matters also.

Induction, not gas.

There is a bit less to worry about. Does your range require ventilation per mfg specification?

Going beyond 400cfm is a big commitment.

Perspective note to beginners: There is always make-up air. The air that flows out of the house via the hood system exactly equals that which flows into the house somehow. The more restrictive the inflow, the lower the outflow.

Low restriction passive MUA