• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

nonrated duct through 2 story apartment building

Y

Yikes

Gold Member
Joined
Nov 2, 2009
Messages
3,075
Location
Southern California
2-story, Type V-A (1 hour) wood-framed apartment building, sprinklered per NFPA 13R. The 18 units are “flats”, meaning that the upstairs and downstairs are two separate (stacking) units.

I want to run the 7” dia. range hood and bathroom exhaust fan ducts from the first floor across through (1) a horizontal nonrated gyp board soffit below the rated floor-ceiling assembly, then up (2) penetrating the 1 hour floor-ceiling assembly, then (3) through a nonrated furred gyp board wall in the back of a closet in the 2nd floor unit, then finally (4) through the 1-hour roof assembly. The ducts run individually, and do not open into the second floor unit.

Can I do this with no rated shaft and no fire or radiation dampers?

CBC 707.2 (in the 2010 codes, it’s 708.2) exception #1 says “a shaft enclosure is not required for openings totally within an individual dwelling unit and connecting four stories or less.” Obviously, I’m less than 4 stories, and in the scenario I described above, it sounds like I am not “opening” the first floor-apartment duct into the second floor-apartment unit, even though I’m only separated from it by a nonrated furred wall? I guess I've confused myself as to whether the term "opening" refers to a penetration of a fire rated assembly, or to an actual atmospheric connection between the units. The latter means I could do this without shafts or dampers, right?
 
What do you believe is the least expensive system for vducting the first story apartment fans upto the roof?

Back in the good ol' days, UBC 711.3 said "In one- and two-story buildings other than group I occupancies, gas vents, DUCTS, piping and factory-built chimneys that extend through not more than two floors need not be enclosed [i.e. in a shaft], provided the openings around the penetrations are firestopped at each floor".

Is there an equivalent in the IBC?
 
712.4 Horizontal assemblies.

Penetrations of a floor, floor/ceiling assembly or the ceiling membrane of a roof/ceiling assembly shall be protected in accordance with Section 707.

712.4.1 Fire-resistance rated assemblies.

Penetrations of the fire-resistance rated floor, floor/ceiling assembly or the ceiling membrane of a roof/ceiling assembly shall comply with Sections 712.4.1.1 through 714.4.1.5

Sounds like a shaft

Sounds like a Dwelling unit seperation issue

sounds like a penetrated rated horizintal assembly

and a rated wall assembly if its bearing.

There is a method of using a subduct assembly into a rated shaft assembly that is used in hotels to link bath exhausts if that works for you??
 
I would rather use conventional fans inside the apartment below, than rooftop fans at the top of a subduct system.

Architect 1281 I agree that's what it sounds like - - but knowing that the creation of the IBC involved so many compromises amongst the various regional codes, I just have a hard time accepting that the IBC is so much more restrictive than the old UBC when it comes to ducts in this commonplace 2-story situation.
 
The CBC exerpt would not apply, as the opening is not "totall within an individual dwelling unit" The opening is the breach in the fire resistive construction.

CBC is generally similar to IBC, so look at 716, which is the place to go for duct penetrations.

716.6.1 Through penetrations.

In occupancies other than Groups I-2 and I-3, a duct constructed of approved materials in accordance with the International Mechanical Code that penetrates a fire-resistance-rated floor/ceiling assembly that connects not more than two stories is permitted without shaft enclosure protection, provided a listed fire damper is installed at the floor line or the duct is protected in accordance with Section 712.4. For air transfer openings, see Exception 7 to Section 707.2.

Exception: A duct is permitted to penetrate three floors or less without a fire damper at each floor, provided it meets all of the following requirements:

1. The duct shall be contained and located within the cavity of a wall and shall be constructed of steel not less than 0.019 inch (0.48 mm) (26 gage) in thickness.

2. The duct shall open into only one dwelling or sleeping unit and the duct system shall be continuous from the unit to the exterior of the building.

3. The duct shall not exceed 4-inch (102 mm) nominal diameter and the total area of such ducts shall not exceed 100 square inches (0.065 m2) in any 100 square feet (9.3 m2) of floor area.

4. The annular space around the duct is protected with materials that prevent the passage of flame and hot gases sufficient to ignite cotton waste where subjected to ASTM E 119 time-temperature conditions under a minimum positive pressure differential of 0.01 inch (2.49 Pa) of water at the location of the penetration for the time period equivalent to the fire-resistance rating of the construction penetrated.

5. Grille openings located in a ceiling of a fire-resistance-rated floor/ceiling or roof/ceiling assembly shall be protected with a listed ceiling radiation damper installed in accordance with Section 716.6.2.1.

Sounds like no shaft, no damper, just some pooky around the penetration.
 
provided it meets all of the following requirements

Since you can't meet all the requirments, a fire damper will be required since it is over 4". (I see now that you did say 7"). But still, no shaft. This needs to be a "real" fire damper, not just a radiation damper, since the duct is penetrating the entire rated floor-celing assembly.
 
Recirculating "range hood" beneath microwave.

The neighbors don't want to smell the liver and onions.
 
Yeah, we always used to do recirculating hoods, which is why it's taken me several years to get around to asking this question. Now the affordable housing funders are demanding ducted hoods, so I'm finally having to face the issue head-on.
 
Yikes said:
2-story, Type V-A (1 hour) wood-framed apartment building, sprinklered per NFPA 13R. The 18 units are “flats”, meaning that the upstairs and downstairs are two separate (stacking) units.I want to run the 7” dia. range hood and bathroom exhaust fan ducts from the first floor across through (1) a horizontal nonrated gyp board soffit below the rated floor-ceiling assembly, then up (2) penetrating the 1 hour floor-ceiling assembly, then (3) through a nonrated furred gyp board wall in the back of a closet in the 2nd floor unit, then finally (4) through the 1-hour roof assembly. The ducts run individually, and do not open into the second floor unit.

Can I do this with no rated shaft and no fire or radiation dampers?

CBC 707.2 (in the 2010 codes, it’s 708.2) exception #1 says “a shaft enclosure is not required for openings totally within an individual dwelling unit and connecting four stories or less.” Obviously, I’m less than 4 stories, and in the scenario I described above, it sounds like I am not “opening” the first floor-apartment duct into the second floor-apartment unit, even though I’m only separated from it by a nonrated furred wall? I guess I've confused myself as to whether the term "opening" refers to a penetration of a fire rated assembly, or to an actual atmospheric connection between the units. The latter means I could do this without shafts or dampers, right?
Click to expand...
i think you should use conventional fans inside the apartment to be safe
 
welcome icondrive

how do did you find us??

are you an inspector, reviewer, arch, other???
 
You must log in or register to reply here.
Top