IECC Vestibule Requirement and 3000 SF Exception

[MKALLAY]

I am looking at a project where the application of IECC (2018) Section C402.5.7 Vestibules is in question. One area of the project (Dormitory, mixed use) has what can best be called a tenant space - essentially a café - that is accessed directly from the exterior. This area is completely separate from the rest of the floor area, the entire tenant space is less than 3000 sq. ft., and so I believe exception 4 of the referenced section applies:

(Vestibules are not required for) doors that open directly from a space less than 3,000 square feet (298 m2) in area.

What is less clear is that there are entrance doors at a lobby space that is well under 3000 sq. ft., but that lobby is atmospherically connected to corridors and other spaces such that the aggregate area will exceed 3000 sq. ft. In this case, it seems to me that the intent of the code would be that a vestibule should be provided, even though the lobby itself is less than needed to meet the exception. Is this correct? And then - what if the lobby is separated from all other areas by doors that are normally kept closed? Would that meet the requirement? In other words - is the exception be based on the specific enclosed room that the entrance opens into, or does it apply to the entire floor area served by that entrance?

 

[steveray]

I say 3000ft without intervening doors....

 

[Henchalwoog]

Doesn't the IECC allow for air curtains? Our version 2012 does not but I believe the 2018 did...

 

[MKALLAY]

Yes - Exception 7 listed in the code section listed above.

 

[Sifu]

I say 3000ft without intervening door

Thats the way I look at it.

 

[MKALLAY]

Thats the way I look at it.

That is the direction the designer took. That said - 3000 sq. ft. is a pretty big lobby space!!

 

[steveray]

The funny thing is they don't define it or put any performance requirements on it....Soooo.....Open ceiling and as many "holes" in it as you want....

C402.6.6​

Building entrances shall be protected with an enclosed vestibule. Doors opening into and out of the vestibule equipped with self-closing devices. Vestibules shall be designed so that in passing through the vestibule it is not necessary for the interior and exterior doors to open at the same time. The installation of one or more revolving doors in the building entrance shall not eliminate the requirement that a vestibule be provided on any doors adjacent to revolving doors.

Exceptions: Vestibules are not required for the following:

1. 1.
   Buildings in Climate Zones 0 through 2.
2. 2.
   Doors not intended to be used by the public, such as doors to mechanical or electrical equipment rooms, or intended solely for employee use.
3. 3.
   Doors opening directly from a sleeping unit or dwelling unit.
4. 4.
   Doors that open directly from a space less than 3,000 square feet (298 m2) in area.
5. 5.
   Revolving doors.
6. 6.
   Doors used primarily to facilitate vehicular movement or material handling and adjacent personnel doors.
7. 7.
   Doors that have an air curtain unit with a velocity of not less than 6.56 feet per second (2 m/s) at 6 inches (152 mm) above the floor that has been tested in accordance with ANSI/AMCA 220 or ISO 27327-1 and installed in accordance with the manufacturer’s instructions. Manual or automatic controls shall be provided that will operate the air curtain unit with the opening and closing of the door and comply with Section C403.4.1.5. Air curtain units and their controls shall comply with Section C408.2.3.

 

[wmott]

I once had a plan reviewer take the 3,000 SF to mean the area served by HVAC equipment.
This was for a 3,500 SF retail space. Sales floor was less than 3,000 SF, and the stock room separated by partitions and doors took the remainder of the space.
The entire 3,500 SF space was served by (1) RTU. So the reviewer determined a vestibule was required.
This only happened this one time.
All other projects (100s and 100s) all took the opinion it was the floor area of the room/space open to the entry.