Any thoughts appreciated here. I recently had a conversation with my AHJ regarding the CFM requirements for residential range hoods. Mechanical code says nothing useful, IRC says 100 CFM intermittant/25 CFM continuous. >400cfm requires a makeup air unit. All fine. However, some of the inspectors are of the opinion that the AHJ has the right to reference the range manufacture's recommendations/requirements for hood CFM rather than the code- apparently based on total BTU output of the range. I understand that code is the minimum standard. I also appreciate and respect the importance of indoor air quality, mechanical ventilation etc. However, two issues come up here. 1. range manufacturers vary widely in their recommendations, some have none at al, many just reference a "pairing" of their own hoods with their ranges. 2. makeup air units for a cold climate are incredibly expensive and complex. We avoid these in all cases except for the really big 42"+ commercial style home ranges. First question is, at what threshold do we really concern ourselves with 400CFM being inadequate to vent a gas range. Second question is, if the range is electric, or induction, what are the criteria for CFM? If its a BTU output issue, a 48" induction range can put out some serious heat, comparable with a gas range, albeit without the combustion byproducts.
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Residential Range Hood CFM requirements
- Thread starter MTDB
- Start date
ADAguy
Registered User
Waiting for this answer, maybe also check with fire insurance carrier. also if a wok is included it may be an additional issue.
Beniah Naylor
SAWHORSE
We don't check residential range hoods. No one has ever showed me the manufacturer's instructions for that kind of equipment, and I have never asked to see them. That doesn't mean that there is no cause for concern, just that I have never been concerned about that issue.
Domestic cooking exhaust equipment is required to be listed to specific UL standards (M1503.2). If you don't follow the manufacturer's instructions, you void the listing. If the manufacturer specifically requires a more powerful exhaust system, you have to install one to meet code.
Keep in mind that meeting code and passing inspections are two different things.
klarenbeek
Silver Member
If the range manufacturer "recommends" something, that's exactly what it is, a recommendation, not an enforceable requirement. The IRC actually has no requirement for a hood above a range, including a gas range, unless its an open top broiler. The kitchen ventilation can be accomplished either with a range hood or just general exhaust from the kitchen, like from an HRV. A recirculating hood would not satisfy the ventilation requirement.
klarenbeek
Silver Member
The requirement for makeup air over 400 CFM is actually not for the range, but to prevent drafting issues for other appliances in the house like the water heater or a wood fireplace. Any version of the code after 2018 doesn't require makeup air if all fuel burning appliances that are vented are either direct vented or power vented. A house with a direct vent furnace, direct vent gas fireplace, and an electric water heater doesn't need makeup air.
ADAguy
Registered User
A big ouch, not a lot of grease fires out your way?
Inspector Gift
Sawhorse - Made in USA
Thanks for posting your comments and questions regarding the cfm requirements for residential range hoods. I work in Oregon and we require 150 cfm intermittent. But ironically, we also allow "listed and labeled ductless range hoods... not... required to exhaust to discharge to the outdoors. There are 2 conditions.
Personally, I have seen too many single family homes that have moisture problems due to recirculating kitchen hoods or insufficient ventilation rates. Montana and Oregon used to have the same requirements. I wonder why things have changed.
klarenbeek
Silver Member
Another example of where the code it the minimum requirement, not best practice. We do a fair amount of canning so I made sure to get our (originally) recirculating hood ducted to the outside.
Grease is another matter. Residential hoods are primarily for heat, moisture, and odor extraction. Most of the grease ends up on the stove, surrounding surfaces, some in the charcoal filter, and some in the duct. They are not designed to prevent grease fires the way a commercial hood is.
Grease is another matter. Residential hoods are primarily for heat, moisture, and odor extraction. Most of the grease ends up on the stove, surrounding surfaces, some in the charcoal filter, and some in the duct. They are not designed to prevent grease fires the way a commercial hood is.
Genduct
Registered User
You really nailed the problem by dividing the arear of Concerns:
The "smells" of the cooking Process (maybe the grease could be concern) AND the need for Combustion Air to feed the Nat Gas Stove/ oven
Given the relative short duration of use of these appliances, Nat Infiltration and average quanity of thise smells, seems someone has formally or informally determined the sizing of the exhaust fan.
Great thought about the recid fan that is meant to "Capture" the incidential gresses
Great topic and thought provoking responses
Genduct
Registered User
PS neglected to continue your great observation about Electric Appliances