Thread: Kitchen Exhaust

This is probably more California-specific because we have some additional codes, but any answer will be welcome.

A question came up at our last chapter meeting regarding the requirement for kitchen exhaust. One of the inspectors has been told that the kitchen hood is required to exhaust to the exterior, but was unable to find a reference.


My memory is that over-range hoods in residential construction are required as of the 2016 CMC to exhaust to the exterior, but I was unable to find it in the California Mechanical Code, California Residential Code or Green Building Standards.


I found the requirement for bathroom exhaust in the CMC (402.5) which refers to the Green Code (4.5.06).


The requirement for kitchen hoods to exhaust to the exterior might be a local ordinance. If no one has anything specific, I will check with that town. Maybe they have it on their website.

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Kitchen hoods are not required for residential unless the cooking appliance manufacturer requires a hood.

Residential hoods are not required to exhaust to the outdoors unless required by the manufacturer.

The above are also subject to state / county / local amendments which may require such exhausting to the outdoors.

Kitchen hoods are also not in place of clearance to combustible material unless so listed or meet code requirements for specified materials and thickness.

Thanks Jerry,

I wonder where I got the exhaust to the exterior requirement. Oh, well... Probably old age.

Over the past year I am seeing a number of high end appliance manufacturers non duct recirculating range hoods.
Not to worry Gunner.
Manufacturer trumps the call.

The issue becomes a bit more interesting (or confusing). The City of Petaluma does state that vented range hoods are required and then cites two codes and an ASHRAE standard. One from the California Mechanical Code (based on the UMC) and the other seems to be from the California Energy Code (CEnC). But, CMC 504.2 is about the back draft, damper - not a ducted hood, CEnC 150.1 is about whole-house ventilation (there is no Exc. 5) and there is also no CEnC 152.0 I don't have the ASHRAE standard. Unless CEnC is not the California Energy Code... but then, I don't know what it could be.

The only thing that I can think of is that this is a local ordinance.

From the City of Petaluma's website:

• In kitchen specify the local exhaust system vented tooutdoors shall have a minimum exhaust rate of 100 cfm.[CEnC 150(o), Exc. 5 to 152(a) & ASHRAE Std. 62.2]
  
• A ducted residential exhaust hood is required. A metal,smooth interior surface duct required on vent hood ordown draft exhaust vent. Aluminum flex duct is notapproved. Provide back draft damper [CMC 504.2]
  
• Add this note to the plans: Upper cabinets shall be aminimum of 30” above cooking top or a hood is to beinstalled per manufacturer’s requirements with clearancesas required by the range/cook top manufacturer’sinstallation instructions. Provide minimum clearances tocombustible materials per [CMC 916.1.2]"

From the 2016 California Energy Code

CEnC 150.1 (0) Ventilation for indoor air quality. All dwelling units shall meet the requirements of ASHRAE Standard 62.2. Ven*tilation and Acceptable Indoor Air Quality in Low-Rise Resi*dential Buildings. Window operation is not a permissible method of providing the whole-building ventilation airflow required in Section 4 of that ASHRAE Standard 62.2. Contin*uous operation of central forced air system air handlers used in central fan integrated ventilation systems is not a permissi*ble method of providing the whole-building ventilation air*flow required in Section 4 of ASHRAE Standard 62.2. Additionally, all dwelling units shall meet the following requirements:
I. Field verification and diagnostic testing.
A. Airflow performance. The whole-building ventila*tion airflow required by Section 4 of ASHRAE Standard 62.2 shall be confirmed through field veri*fication and diagnostic testing in accordance with the applicable procedures specified in Reference Residential Appendix RA3.7

Much,many thanks Gunner, for the information. Great info.

As for, From the 2016 California Energy Code
CEnC 150.1 (0) Ventilation for indoor air quality. All dwelling units shall meet the requirements of ASHRAE Standard 62.2. Ven*tilation and Acceptable Indoor Air Quality in Low-Rise Resi*dential Buildings.
CEnC 150.1 (0) Ventilation for indoor air quality. and would not pertain to recirculating hoods or appliances, ie built in microwave recirculation.

Likely the mention is for HRV and ERV system particle and energy count. But I could be mistaken.

Jerry, Bob, Garry, you views on the subject or code?

We try to avoid quoting code when possible. This is one of our standard statement concerning non venting kitchen fans. ( Kitchen exhaust fan does not vent to exterior. Exhaust fans should exhaust to the exterior, to ensure moist air is vented to the outside of the home, and to reduce humidity inside the home. It is important to note that non ducted, recirculating kitchen range hoods provide no real ventilation – they simply recirculate the air collected from the cooktop back into the kitchen. They do not reduce moisture and have limited value in managing odors. For optimal kitchen air quality, always use kitchen range hoods, downdraft kitchen exhausters or fans, which vent directly to the outside of the home )

Originally Posted by Steven Abbott

We try to avoid quoting code when possible. This is one of our standard statement concerning non venting kitchen fans. ( Kitchen exhaust fan does not vent to exterior. Exhaust fans should exhaust to the exterior, to ensure moist air is vented to the outside of the home, and to reduce humidity inside the home. It is important to note that non ducted, recirculating kitchen range hoods provide no real ventilation – they simply recirculate the air collected from the cooktop back into the kitchen. They do not reduce moisture and have limited value in managing odors. For optimal kitchen air quality, always use kitchen range hoods, downdraft kitchen exhausters or fans, which vent directly to the outside of the home )

I have something of a problem with the above statement. Not all kitchen fans are exhaust fans and thereby not required to vent outdoors. True, an exhaust fan should, by definition of the word 'exhaust', vent to the outside. In Ca, basically the only fans I see that are required to vent outdoors is a downdraft and that's either by local code or manufacturers recommendation. If the fan is built in to the microwave I check to see if the fan has been reversed during install to vent to the outside via ducting and if not, I mention it in the report.

Originally Posted by Ian Page

True, an exhaust fan should, by definition of the word 'exhaust', vent to the outside.

Ian pointed out an excellent aspect - "exhaust" versus "cooking hood" or even "vent".

All cooking hoods which are "exhaust" ... "exhaust" to the outdoors ... all others are simply "cooking hoods" and typically are recirculating designs, typically with grease filters and even charcoal filters.

There is absolutely nothing wrong with recirculating cooking hoods.

To say there is, you might as well point out that all incandescent lamps "should" be replaced with LED, that all non-dimmer switches "should" be replaced with dimming switches, the list of "should" items is endless ... depending on the whims of the inspector.

Originally Posted by Jerry Peck

Ian pointed out an excellent aspect - "exhaust" versus "cooking hood" or even "vent".

All cooking hoods which are "exhaust" ... "exhaust" to the outdoors ... all others are simply "cooking hoods" and typically are recirculating designs, typically with grease filters and even charcoal filters.

There is absolutely nothing wrong with recirculating cooking hoods.

To say there is, you might as well point out that all incandescent lamps "should" be replaced with LED, that all non-dimmer switches "should" be replaced with dimming switches, the list of "should" items is endless ... depending on the whims of the inspector.

Of course if you feel that a recirculating fan does not pose a problem that is your call But here in Washington state when I enter a house and find electric baseboard heating, a bathroom with no fan because it has an operable window and a recirculating fan sitting over a gas cook top I am going to spend quite a bit of time explaining the negative ramifications of these issues.

- - - Updated - - -

Originally Posted by Jerry Peck

Ian pointed out an excellent aspect - "exhaust" versus "cooking hood" or even "vent".

All cooking hoods which are "exhaust" ... "exhaust" to the outdoors ... all others are simply "cooking hoods" and typically are recirculating designs, typically with grease filters and even charcoal filters.

There is absolutely nothing wrong with recirculating cooking hoods.

To say there is, you might as well point out that all incandescent lamps "should" be replaced with LED, that all non-dimmer switches "should" be replaced with dimming switches, the list of "should" items is endless ... depending on the whims of the inspector.

Of course if you feel that a recirculating fan does not pose a problem that is your call But here in Washington state when I enter a house and find electric baseboard heating, a bathroom with no fan because it has an operable window and a recirculating fan sitting over a gas cook top I am going to spend quite a bit of time explaining the negative ramifications of these issues.

Originally Posted by Steven Abbott

We try to avoid quoting code when possible.

"We"? Got a mouse in your pocket, Steven?

I agree about quoting code and I write something very similar to what you posted. This was just in reference to something that a colleague of mine had been told and I was just trying to follow-up and get specifics. A part of the eternal learning that is home inspection.

Originally Posted by Steven Abbott

... a bathroom with no fan because it has an operable window and a recirculating fan sitting over a gas cook top I am going to spend quite a bit of time explaining the negative ramifications of these issues.

Somehow, you made a giant leap from kitchen cooking hood to a bathroom

What negative ramifications does a non-vented (recirculating) cooking hood present?