# Mech Exhaust Required in Residential Kitchens



## mstehlin

I got dinged by the plan examiner for the first time, requiring an exhaust from each kitchen in an apartment project.  I have done many multi-family residential rehabs and we have always installed recirculating hoods with charcoal filters in kitchens with operable windows.  We have done this, because ducting a hood to the exterior is a nightmare in multi-family buildings, especially some I work on that are in urban neighborhoods with masonry bearing walls built to the property line.

It looks like IMC Table 403.3 footnote b and f are the relevant code sections.   When I look at an older code (2003), I see that the wording of footnote b has not changed ("mechanical exhaust required..."), but it was not previously a footnote for kitchens, only bathrooms, smoking lounges, nail salons, etc...

I also see this is now a requirement in single family houses too: IRC 1507.3

One question though:  is a hood even required?  Seems like you could install a 100 CFM bathroom type vent in the ceiling and eliminate the hood and still meet code.


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## cda

gas or electric


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## mstehlin

All electric


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## RJJ

What code is in effect in your area. latest year?

If these are apartments do you through the owner have access to the units above etc?


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## mstehlin

Our Ohio code for both residential and commercial is based on the 2009 ICC codes.

I can solve the problem this time, I was just bringing up to this forum because I was totally surprised to see that 100 CFM of mechanical exhaust is now required in EVERY residential kitchen both in multi-family and single family.   IRC 1507.3 and IBC 403.3 footnote b

For some reason I never saw this requirement until today.  I think it is overkill.  Most new single family houses already do this, but I really don't like installing ducted hoods in apartments.  The duct will collect grease and be a hazard eventually.  Plus you most likely have to install them in a soffit so you are not into the rated separation.  Then you must discharge them 10' from a property line and away from operable windows etc.


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## jar546

This is news to me.  When did this change?  Not in the 2009 IRC...


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## mark handler

http://web.ornl.gov/sci/buildings/2012/2004%20B9%20papers/012_Password_Removed.pdf


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## mtlogcabin

401.2 Ventilation required.

Every occupied space shall be ventilated by natural means in accordance with Section 402 or by mechanical means in accordance with Section 403

If you have an open-able window in a residential kitchen then a mechanical exhaust is not required


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## jar546

mtlogcabin said:
			
		

> 401.2 Ventilation required.Every occupied space shall be ventilated by natural means in accordance with Section 402 or by mechanical means in accordance with Section 403
> 
> If you have an open-able window in a residential kitchen then a mechanical exhaust is not required


Agree.  If you don't have natural then you have to have mechanical and IF you have mechanical, those numbers/rates apply.  Mechanical is NOT required in kitchens if you have natural.


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## RJJ

I agree! That is why I asked for code year! I was thinking they may have added a new twist.


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## fatboy

Looks like all of 403 was re-written in 2009, except 403.5.


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## mstehlin

I disagree that a window allows you to eliminate the required mechanical exhaust in a multi-family kitchen

IBC 2009 Table 403.3, Private Dwellings - Kitchens, has footnote b, which reads: ""Mechanical exhaust REQUIRED"

Since I do not have a 2009 IBC handy, I suppose this could be a footnote unique to Ohio, but I doubt it.  Maybe it is a typo?

After re-reading the residential code, I do see that 1507.1 does say "where mechanically ventilated" ...the rate must be 100 CFM.  So, I agree, natural ventilation is allowed in one and two-family dwelling's kitchens.


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## mstehlin

View attachment 910


Mark Handler linked to ASHRAE's first residential ventilation standard, which says mechanical ventilation is required because windows are not sufficient.
	

		
			
		

		
	

View attachment 910


/monthly_2013_10/Standard-62.2-Kitch.jpg.71f8887245047d1eebf2eaca622eca25.jpg


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## Gregg Harris

mstehlin said:
			
		

> I disagree that a window allows you to eliminate the required mechanical exhaust in a multi-family kitchen IBC 2009 Table 403.3, Private Dwellings - Kitchens, has footnote b, which reads: ""Mechanical exhaust REQUIRED"
> 
> Since I do not have a 2009 IBC handy, I suppose this could be a footnote unique to Ohio, but I doubt it.  Maybe it is a typo?
> 
> After re-reading the residential code, I do see that 1507.1 does say "where mechanically ventilated" ...the rate must be 100 CFM.  So, I agree, natural ventilation is allowed in one and two-family dwelling's kitchens.


I think you mean IMC 403.3 for kitchen is not (b) but  (g) and does not require mechanical


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## mstehlin

View attachment 911


View attachment 912


Here are images from Table 403.3 of the 2011 Ohio Mech Code, based on the 2009 IMC.  The footnote is b, and Mech exhaust is required.  Maybe this is unique to Ohio.
	

		
			
		

		
	

View attachment 911


View attachment 912


/monthly_2013_10/Table403.3.jpg.5ea8007f406305d5d66a63461955bdd0.jpg

/monthly_2013_10/footnote.jpg.0f6a46950bb903ffa9dbbdbcd49b0348.jpg


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## mtlogcabin

2012 IMC

SECTION 505

DOMESTIC KITCHEN EXHAUST EQUIPMENT

505.1 Domestic systems.

Where domestic range hoods and domestic appliances equipped with downdraft exhaust are located within dwelling units, such hoods and appliances shall discharge to the outdoors through sheet metal ducts constructed of galvanized steel, stainless steel, aluminum or copper. Such ducts shall have smooth inner walls, shall be air tight, shall be equipped with a backdraft damper, and shall be independent of all other exhaust systems.

Exceptions:

1.	Where installed in accordance with the manufacturer’s installation instructions and where mechanical or natural ventilation is otherwise provided in accordance with Chapter 4, listed and labeled ductless range hoods *shall not be required to discharge to the outdoors.*


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## Frank

2006 IMC allowed for natural ventilation of the kitchen, including alcove kitchens

2009 IMC 403.3 added note B mechanical exhuast required, no more recirc fans on range hoods.

The exception in MTlogcabin's post below is an artifact from previous codes and only addresses downdraft exhaust systems--the note B in Table 403.3 likely makes this exception moot.


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## Gregg Harris

Frank said:
			
		

> 2006 IMC allowed for natural ventilation of the kitchen, including alcove kitchens2009 IMC 403.3 added note B mechanical exhuast required, no more recirc fans on range hoods.
> 
> The exception in MTlogcabin's post below is an artifact from previous codes and only addresses downdraft exhaust systems--the note B in Table 403.3 likely makes this exception moot.


I agree Frank, I pulled 06 when checking and posted (g), and then noticed when I pulled 09 it was changed for 09, and 12 with (b) requiring mechanical.


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## mtlogcabin

What I posted is out of the 2012 Mechanical Code. The exception is not limited to down draft exhaust systems

505.1 Domestic systems.

Where domestic range hoods *and* domestic appliances equipped with downdraft exhaust

Read it again the Section includes all domestic systems. It is not referencing down draft systems exclusively. 

If a hood does not vent to the outside then it is not a mechanical ventilation system and it is not required to meet Section 403 then the room (kitchen) must have natural ventilation meeting the requirements of Section 402


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## RJJ

MT he is referring to 2009. IMC should be the code. It does have a footnote and requires exhausted ducts to the outside. See table 403.3 min vent rates.


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## mtlogcabin

IMC 505 is the same in the 06, 09 & 12 codes

Section 505 is the Charging language specific to domestic kitchen exhaust systems. It does not require a range hood or down draft system be installed but if you choose to put one in, here are the requirements and exceptions.

Exception 1 includes all listed and labeled ductless range hoods

If it is ductless you can't vent it to the outside.

Every occupied space shall be ventilated by natural means in accordance with Section 402 *or* by mechanical means in accordance with Section 403.

Designers choice

Example

The kitchen in an apartment is interior adjacent to the corridor wall. Natural ventilation can not be met because there is no window in the kitchen. Now a mechanical exhaust system is required for the kitchen. Nothing requires a hood the only requirement is makeup air which can be handled by the HVAC and an exhaust system to the outside which will remove 100% of the amount of air supplied to the kitchen.

Now move that kitchen to an exterior wall with a properly sized window and no exhaust is required from the kitchen regardless if a listed ductless range hood is installed or not per IMC 505

Table 403.3 footnote b does not require a mechanical exhaust system it simply states if you install one it must vent to the outside and remove 100% of the air supplied to the space.

403.2.1

3.	Where mechanical exhaust is required by Note b in Table 403.3, recirculation of air from such spaces shall be prohibited. All air supplied to such spaces shall be exhausted, including any air in excess of that required by Table 403.3.

MECHANICAL EXHAUST SYSTEM. A system for removing air from a room or space by mechanical means.

A] 102.1 General.

Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall govern

I would argue 505 is specific to domestic kitchen exhaust equipment and is more specific than a footnote in a ventilation table


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## Gregg Harris

mtlogcabin said:
			
		

> IMC 505 is the same in the 06, 09 & 12 codesSection 505 is the Charging language specific to domestic kitchen exhaust systems. It does not require a range hood or down draft system be installed but if you choose to put one in, here are the requirements and exceptions.
> 
> Exception 1 includes all listed and labeled ductless range hoods
> 
> If it is ductless you can't vent it to the outside.
> 
> Every occupied space shall be ventilated by natural means in accordance with Section 402 *or* by mechanical means in accordance with Section 403.
> 
> Designers choice
> 
> Example
> 
> The kitchen in an apartment is interior adjacent to the corridor wall. Natural ventilation can not be met because there is no window in the kitchen. Now a mechanical exhaust system is required for the kitchen. Nothing requires a hood the only requirement is makeup air which can be handled by the HVAC and an exhaust system to the outside which will remove 100% of the amount of air supplied to the kitchen.
> 
> Now move that kitchen to an exterior wall with a properly sized window and no exhaust is required from the kitchen regardless if a listed ductless range hood is installed or not per IMC 505
> 
> Table 403.3 footnote b does not require a mechanical exhaust system it simply states if you install one it must vent to the outside and remove 100% of the air supplied to the space.
> 
> 403.2.1
> 
> 3.	Where mechanical exhaust is required by Note b in Table 403.3, recirculation of air from such spaces shall be prohibited. All air supplied to such spaces shall be exhausted, including any air in excess of that required by Table 403.3.
> 
> MECHANICAL EXHAUST SYSTEM. A system for removing air from a room or space by mechanical means.
> 
> A] 102.1 General.
> 
> Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall govern
> 
> I would argue 505 is specific to domestic kitchen exhaust equipment and is more specific than a footnote in a ventilation table


I would agree with you the first word of 505.1 is "Where" where it is installed with, not "it shall be installed with"


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## RJJ

After reading and re reading this I would have to agree. Good posts MT and Gregg.


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## mstehlin

"I would argue 505 is specific to domestic kitchen exhaust equipment and is more specific than a footnote in a ventilation table"

But... footnote b says mechanical ventilation is required in the kitchen.  It does not say that the hood must be the ventilation method.  In fact it doesn't say anything about hoods.

A ceiling exhaust fan, similar to a bath fan would comply if it was 100 CFM intermittent or 20 CFM constant.

Can someone with the 2009 and 2012 IMC confirm that Kitchens do indeed have footnote b, so I can understand whether this is just an Ohio issue?


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## Gregg Harris

mstehlin said:
			
		

> "I would argue 505 is specific to domestic kitchen exhaust equipment and is more specific than a footnote in a ventilation table"But... footnote b says mechanical ventilation is required in the kitchen.  It does not say that the hood must be the ventilation method.  In fact it doesn't say anything about hoods.
> 
> A ceiling exhaust fan, similar to a bath fan would comply if it was 100 CFM intermittent or 20 CFM constant.
> 
> Can someone with the 2009 and 2012 IMC confirm that Kitchens do indeed have footnote b, so I can understand whether this is just an Ohio issue?


Foot note (b) is in both 09 and 12 but you are dealing with 2 different sections.

401.1 Scope.

This chapter shall govern the ventilation of spaces within a building intended to be occupied. Mechanical exhaust systems, including exhaust systems serving clothes dryers and cooking appliances; hazardous exhaust systems; dust, stock and refuse conveyor systems; subslab soil exhaust systems; smoke control systems; energy recovery ventilation systems and other systems specified in Section 502 shall comply with Chapter 5.

401.2 Ventilation required.

Every occupied space shall be ventilated by natural means in accordance with Section 402 or by mechanical means in accordance with Section 403. Where the air infiltration rate in a dwelling unit is less than 5 air changes per hour when tested with a blower door at a pressure of 0.2-inch water column (50 Pa) in accordance with Section 402.4.1.2 of the International Energy Conservation Code, the dwelling unit shall be ventilated by mechanical means in accordance with Section 403.


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## mtlogcabin

> Where the air infiltration rate in a dwelling unit is less than 5 air changes per hour when tested with a blower door at a pressure of 0.2-inch water column (50 Pa) in accordance with Section 402.4.1.2 of the International Energy Conservation Code, the dwelling unit shall be ventilated by mechanical means in accordance with Section 403.


I see that is new to the 2012 IMC which could make a big change where I live since the state requires 4 ACH max.

I agree the 2012 will require a kitchen exhaust system in a dwelling designed with less than 5 ACH.

The earlier editions do not

Gregg thanks for finding the change


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## Gregg Harris

mtlogcabin said:
			
		

> I see that is new to the 2012 IMC which could make a big change where I live since the state requires 4 ACH max. I agree the 2012 will require a kitchen exhaust system in a dwelling designed with less than 5 ACH.
> 
> The earlier editions do not
> 
> Gregg thanks for finding the change


Vobis sunt grata

delectalio mea


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## Yikes

Just confriming: out here in California, our California Mechancial Code is based on the UMC, not the IMC, so for multifamily housing in CA there is no requirement for domestic kitchen range to have a hood that discharges to the outdoors.  Corollary: if an apartment happens to happens a domestic range hood that discharges to outdoors, there is no minimum CFM requirement.

Am I correct?


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## mtlogcabin

I believe you do

2012 UMC

Chapter 4 has a lot of changes.

402.1.2 requires dwellings to meet Chapter 4 or ASHRAE 62.2

402.2 requires natural ventilation openings to be permanently open or controls to prevent the opening from being closed while occupied

Same as the 2009 UMC

403.7 requires exhaust ventilation

Table 403.7 Residential kitchens requires 50/100 cfm/unit


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## Gregg Harris

Local Ventilation Exhaust Requirements [

ASHRAE 62.2

, Section 5]

:

In addition to meeting the Whole-Building Ventilation Requirements discussed in the previous

section,

ASHRAE 62.2

requires that

each

kitchen and bathroom have a local ventilation exhaust

system installed that exhausts indoor air to outside the dwelling. The Local Ventilation Exhaust

Requirements in one room can be met by a Whole-Building Ventilation exhaust system installed

in that room (in this case Local Ventilation

Exhaust systems would still have to be installed in

other kitchens and bathrooms where the Whole-Building Ventilation exhaust system is not

installed.) Use of operable windows is not allowed for meeting the local ventilation exhaust.


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## Yikes

I agree that 2009 UMC (2010 CBC) table 4-1 requires ventilation air for the apartment unit.  My mechanical engineer uses a continuous running bathroom fan* (and undercuts in the doors) to achieve this.

That said, I do not see anythign that would ADDITIONALLY require kitchen-specific exhaust.  Table 4-4 has exhaust requirements for "Kitchen-commercial" and "Kitchenettes".  I don't know what the code defintion of a "kitchenette" is, but it doesn't sound like an apartment unit kitchen.

As the OP said, on multifamily housing we are getting squeezed between the requirements of the code to provide exhaust to the outside (and makeup air), vs. the city planning requirements to try and avoid wall-mounted louvers.  On my last project I tried to use a subduct system with roof-mounted exhaust, but the requirement for continuous power meant we had to add a generator to the project.


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