# 2013 CBC 1018.5 Air movement in corridors?



## JPohling (Sep 29, 2015)

I have a project that went back in to plan check for a plan change related to the HVAC ductwork because there were less HVAC units on the roof than the developers plans indicated there would be..  This is a "B" occupancy stand alone pad building for a financial services company.  The building is new.  First generation build out and is fully sprinklered.  The interior corridors are therefore non-rated.

The GC was down there and the plan reviewer said................although these are non rated corridors you still need to comply with 1018.5 " Air movement in corridors".  These corridors are conditioned and there are supply and returns located in the corridors to achieve this.  All returns are ducted.  we are not using the space above the ceiling as a plenum in any way.  I am trying to understand this "NEW" comment?  It doesn't sound correct to me?


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## clear as mud (Sep 29, 2015)

From the 2009 IBC Commentary:

The use of these corridors as part of the air distribution system could render those egress elements unusable. The intent is to have positive pressure in the corridors. Therefore, any air movement condition that could introduce smoke into these vital egress elements is prohibited. It is not the intent of this section to prohibit the air movement necessary for ventilation and space conditioning of corridors, but rather to prevent those spaces from serving as conduits for the distribution of air to, or the collection of air from, adjacent spaces. This restriction also extends to door transoms and door grilles that would allow the spread of smoke into a corridor. This limitation is not, however, intended to restrict slight pressure differences across corridor doors, such as a negative pressure differential maintained in kitchens to prevent odor migration into dining rooms. Note that air distribution via ducted systems located in or above corridors is acceptable since the corridor itself would not be functioning as a duct.


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## cda (Sep 29, 2015)

http://www.ecodes.biz/ecodes_support/free_resources/2013California/13Building/PDFs/Chapter%2010%20-%20Means%20of%20Egress.pdf

If the corridors are not rated, than they can have openings wherever they want and no opening protection is required.

So air is going to go wherever it wants to go.

So it seems like 1018.5 does not apply


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## mtlogcabin (Sep 29, 2015)

> These corridors are conditioned and there are supply and returns located in the corridors to achieve this.


Does the supply and returns for the corridors communicate with other areas of the building? If not you should be good to go. If they do you you may have some more work to do.


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## JPohling (Sep 29, 2015)

The same AHU serves offices as well as the corridor within the same suite.  We have never had this issue previously in any jurisdiction across the US.  I cannot believe that we would somehow need dedicated air handlers to serve the non rated corridors.  like CDA points out there could be a plan that uses cased openings instead of doors so there is no way to separate the air.  I really do not believe that this section applies unless your using the area above the corridor ceiling as a plenum.


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## cda (Sep 29, 2015)

Or have full rated corridor

It is like saying you have a non rated corridor but all of 1018 still applies


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## mtlogcabin (Sep 30, 2015)

ICC Official interpretation

I think you are good to go as long as it is ducted and not using the corridor to move the air.

http://www2.iccsafe.org/cs/committeeArea/pdf_file/BU_03_18_04.pdf

CHAPTER 10MEANS OF EGRESSSECTION 1016.4IBC Interpretation No. 18-042003 EditionIssued: 04-22-051016.4 Air movement in corridors. Exit access corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts.Exceptions:1. Use of a corridor as a source of makeup air for exhaust systems in rooms that open directly onto such corridors, includingtoilet rooms, bathrooms, dressing rooms, smoking lounges and janitor closets, shall be permitted provided that each suchcorridor is directly supplied with outdoor air at a rate greater than the rate of makeup air taken from the corridor.2. Where located within a dwelling unit, the use of corridors for conveying return air shall not be prohibited.3. Where located within tenant spaces of 1,000 square feet (93 m2) or less in area, utilization of corridors for conveyingreturn air is permitted.! ! ! ! ! ! ! ! ! !Q: Can a single HVAC duct system (supply, return, exhaust, relief, or ventilation) serve an exit access corridor andspaces open and/or adjacent to the exit access corridor where the air supplied into and returned out of the open and/oradjacent spaces is through the duct system and not through the exit access corridor?A: Yes. Air supplied from a single HVAC duct system is permitted to serve an exit access corridor and spaces openand/or adjacent to the exit access corridor. Air supplied by the duct system into the spaces open and/or adjacent to theexit access corridor, either by the duct system or by other mechanical or non-mechanical m eans, is not permitted to betransferred into or through the exit access corridor as supply air, return air, make up air, ventilation, or exhaust._________________________________________________________________________


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## cda (Sep 30, 2015)

Non rated corridor =====

No corridor

If the corridor is non rated, the layout can look like anything

The walls could stop within a foot of the ceiling, they could have ten foot openings in the wall to walk thru with no opening protection.

There is no corridor, it might look like one


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## mtlogcabin (Sep 30, 2015)

cda said:
			
		

> Non rated corridor =====No corridor
> 
> If the corridor is non rated, the layout can look like anything
> 
> ...


Agree

CORRIDOR. An enclosed exit access component that defines and provides a path of egress travel.


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## clear as mud (Sep 30, 2015)

Disagree.

Do not confuse a corridor with an unenclosed hallway within a tenant suite. Corridors are specifically defined as "enclosed" "exit access" components.(i.e., leading to an exit) The definition says nothing about a fire resistance rating. Nowhere is 1018 does it say that a corridor is not required in a given situation. It only gives exceptions or reductions to the fire resistance rating. That doesn't mean it can be too narrow for the occupant load, unenclosed, a dead end, or used for air movement. It must still be constructed as, and serve as an exit access component.

While sprinklers provide an alternative protection to the fire resistance rating of the corridor, they do not provide an alternative to the corridor itself. A 0-hour corridor can still provide protection from heat and smoke until the occupants can reach an exit.

jmo


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## cda (Sep 30, 2015)

clear as mud said:
			
		

> Disagree.Do not confuse a corridor with an unenclosed hallway within a tenant suite. Corridors are specifically defined as "enclosed" "exit access" components.(i.e., leading to an exit) The definition says nothing about a fire resistance rating. Nowhere is 1018 does it say that a corridor is not required in a given situation. It only gives exceptions or reductions to the fire resistance rating. That doesn't mean it can be too narrow for the occupant load, unenclosed, a dead end, or used for air movement. It must still be constructed as, and serve as an exit access component.
> 
> While sprinklers provide an alternative protection to the fire resistance rating of the corridor, they do not provide an alternative to the corridor itself. A 0-hour corridor can still provide protection from heat and smoke until the occupants can reach an exit.
> 
> jmo


Than a question

If the building is sprinkled and the non rated corridor provision is used,,,

Are doors required for openings in the corridor ??


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## mtlogcabin (Sep 30, 2015)

The code does not recognize the term "hallway''



> Are doors required for openings in the corridor ??


To meet the definition of "enclosed" I would say yes.

Are doors required at the end of a long corridor? Example where a hotel corridor dumps into a lobby I would say no.


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## Paul Sweet (Sep 30, 2015)

This prohibition has been in the code for some time.  40 or 50 years ago it was not unusual to have louvers in doors to pull room air into the corridor, and the central return louver in the corridor,so the corridor functioned as a return air plenum


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## cda (Sep 30, 2015)

The code allows non rated corridors to be open to adjoining spaces


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## clear as mud (Sep 30, 2015)

cda,

The code commentary under definition of corridor would seem to agree with you. I just happen to disagree. As such, I stated jmo. (just my opinion)

The code does not provide a definition of enclosed but it does define corridor and a fire resistance rating is not part of the definition.

As always,

clear as mud


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## cda (Sep 30, 2015)

clear as mud said:
			
		

> cda,The code commentary under definition of corridor would seem to agree with you. I just happen to disagree. As such, I stated jmo. (just my opinion)
> 
> The code does not provide a definition of enclosed but it does define corridor and a fire resistance rating is not part of the definition.
> 
> ...


Agree not part of the definition but you have to read corridor requirements ,,, if dealing with a rated corridor


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## JPohling (Sep 30, 2015)

How many have seen a dedicated HVAC system for a non rated corridor?  Never in 30 years for me.

went back into some older code books.

2007 CBC  1017.4 Air movement in corridors.  Corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts *when required to be fire-resistive rated in accordance with table 1017.1*

2010 CBC 1018.5 Air movement in corridors.  Corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts.

2013 CBC 1018.5 Air movement in corridors.  Corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts.


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## JPohling (Oct 1, 2015)

So the plan reviewer is still sticking to his correction and the BO has agreed!  WOW  totally shocked.  This was flagged during an over the counter plan change.  The original design was submitted and approved and has been constructed to 40% complete.  Essentially they are saying the only way to achieve this is with a separate dedicated system to serve the corridors.  The corridors have 3 different glass exposures E/S/W sure thats gonna work...................How can they be focused on no mixing of air in ducts or air handlers, but there is no separation between the rooms and the corridors?  NEED ADDITIONAL AMMUNITION


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## mtlogcabin (Oct 1, 2015)

[A] 104.10 Modifications.

Wherever there are practical difficulties involved in carrying out the provisions of this code, the building official shall have the authority to grant modifications for individual cases, upon application of the owner or owner’s representative, provided the building official shall first find that special individual reason makes the strict letter of this code impractical and the modification is in compliance with the intent and purpose of this code and that such modification does not lessen health, accessibility, life and fire safety, or structural requirements. The details of action granting modifications shall be recorded and entered in the files of the department of building safety.

[A] 104.11 Alternative materials, design and methods of construction and equipment.

The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code in quality, strength, effectiveness, fire resistance, durability and safety.

Install smoke detectors in the return to shut the unit down. No air movement in the corridor area if the HVAC unit is not running. 

Do they have a mechanical inspector/plan reviewer who might be able to explain to a building person that the corridor does not serve as a "conduit" for the supply, return, exhaust, relief or ventilation air ducts within the system design.



1018.5 Air movement in corridors.

Corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts.

DUCT. A tube or conduit utilized for conveying air. The air passages of self-contained systems are not to be construed as air ducts.


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## JPohling (Oct 1, 2015)

Thanks MT

I found a 2012 IBC code commentary for 1018.5 that states..........."Note that air distribution via ducted systems located in or above corridors is acceptable since the corridor itself would not be functioning as a duct"  That along with your interpretation from post #7 was sent to the plan reviewer for his perusal.  Hopefully that will be sufficient.   Every room and space has its own independent supply and return ductwork serving the space.  In no way shape or form is the corridor being used as a "DUCT"


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## JPohling (Oct 8, 2015)

Plan checker relented with a couple requirements that are easy for us to comply with.  Smoke detectors in the Air Handler Units tied into the fire alarm panel.  The AHU's did not require detectors individually, but in this jurisdiction they add up the CFM's individually and once over the threshold you need detectors in all units.


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