2013 CBC 1018.5 Air movement in corridors?

[JPohling]

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?

 

[JPohling]

Bump No mechanical plan checkers want to respond?

 

[cda]

how about if you resubmit the plans and do not call the corridors ,,,,,,corridors??

Or take a saws all to the walls, every so often, and there will be no walls

 

[JPohling]

Our plans call them hallways.............I think we are close to resolution

 

[rgrace]

Bump No mechanical plan checkers want to respond?

I'll respond I've been out for a couple of weeks, and haven't had access to the forum, so I apologize for my delayed response.

I do not know what the 2013 CBC 1018.5 says; I assume that it is the same as 2012 IBC 1018.5 or 2012 IMC 601.2, or at least similar.

So here is my take on this section. The purpose of this section is to prevent the corridor (rated or non-rated, doesn't matter) from filling up with smoke during a fire event. The corridor, after all, is an egress element that you want to maintain smoke-free. If an air distribution system served multiple spaces, and one were to locate the return intake of that system in a corridor, the supply-to-return path would naturally flow into the corridor. If one of those spaces served by this air distribution system contained a smoldering fire that created smoke, the smoke would be drawn into the corridor, filling the corridor, and making egress through the corridor deadly. We want to design our systems to prevent this from happening.

I don't know if I completely understand the proposed design that generated this post. It sounds like the design is consistent with what I described above, and I would have concerns with putting a return (ducted or plenum) in that corridor. You are asking the system to draw smoke from other spaces into the corridor by putting a return in the corridor. However, if a corridor were to be provided with a dedicated HVAC system (serving no other spaces except the corridor), the possibility of filling the corridor up with smoke from other spaces would be near nil. This design would be similar (not exact) to that permitted in IBC 1022.6.

Ultimately, if a design looks like it has the capacity to fill an egress corridor up with smoke, redesign the system.

 

[cda]

I'll respond I've been out for a couple of weeks, and haven't had access to the forum, so I apologize for my delayed response.I do not know what the 2013 CBC 1018.5 says; I assume that it is the same as 2012 IBC 1018.5 or 2012 IMC 601.2, or at least similar.

So here is my take on this section. The purpose of this section is to prevent the corridor (rated or non-rated, doesn't matter) from filling up with smoke during a fire event. The corridor, after all, is an egress element that you want to maintain smoke-free. If an air distribution system served multiple spaces, and one were to locate the return intake of that system in a corridor, the supply-to-return path would naturally flow into the corridor. If one of those spaces served by this air distribution system contained a smoldering fire that created smoke, the smoke would be drawn into the corridor, filling the corridor, and making egress through the corridor deadly. We want to design our systems to prevent this from happening.

I don't know if I completely understand the proposed design that generated this post. It sounds like the design is consistent with what I described above, and I would have concerns with putting a return (ducted or plenum) in that corridor. You are asking the system to draw smoke from other spaces into the corridor by putting a return in the corridor. However, if a corridor were to be provided with a dedicated HVAC system (serving no other spaces except the corridor), the possibility of filling the corridor up with smoke from other spaces would be near nil. This design would be similar (not exact) to that permitted in IBC 1022.6.

Ultimately, if a design looks like it has the capacity to fill an egress corridor up with smoke, redesign the system.

Does a non rated corridor require doors,,, if there are cased openings in it????

 

[rgrace]

Does a non rated corridor require doors,,, if there are cased openings in it????

Don't know. That's something I ask our building folks. When I need to know if a building element is "required", I ask them. I am an MEP SME

 

[cda]

Don't know. That's something I ask our building folks. When I need to know if a building element is "required", I ask them. I am an MEP SME

Well for grins if they said "no doors were required in a non rated corridor",,,

Would that change your answer??

 

[JPohling]

they relented and just made us install duct detectors at the AHU's...............

I do not believe doors are required in a non rated corridor.

 

[cda]

they relented and just made us install duct detectors at the AHU's...............I do not believe doors are required in a non rated corridor.

Yea!!! Un common sense prevails!!

 

[rgrace]

Well for grins if they said "no doors were required in a non rated corridor",,,Would that change your answer??

For the record ..... No. If the corridor/hallway met the definition of a corridor in the IBC, doors or no doors, my response would be the same.

 

[cda]

For the record ..... No. If the corridor/hallway met the definition of a corridor in the IBC, doors or no doors, my response would be the same.

Well if no doors in any openings of the corridor, smoke will migrate. Just a point.

I would say no doors are required

 

[rgrace]

Well if no doors in any openings of the corridor, smoke will migrate. Just a point.I would say no doors are required

Migrate, perhaps, but not forced in by mechanical means.

 

[cda]

Fires create pressure, yes not mechanical pressure.

 

[Builder Bob]

Are the returns and supplies in the corridors supplying the same areas adjacent to the corridor...... wing A with offices on each side. In essence, the HVAC system that supplies the corridor cannot share returns or supplies with the offices unless special provisions are made. This is to provide a higher level of protection for the egress path in emergencies......

 

[cda]

I guess the fire and smoke will not know that it cannot go through the cased openings in the corridor walls?

 

[JPohling]

Yes, same system serves the non rated corridor and adjacent spaces to the corridor. All rooms, spaces and corridors have their own supply and returns. This is completely allowed per code.