Bath fans in rated celings

[ndtolearn]

Hi all,

We are reviewing plans for a two story apartment building with stacked units so the floor/ceiling assembly will be 1-hour rated. The designer is proposing to install the bathroom exhaust fans in the wall and send the duct up through the top plates rather than installing the bath fan in the ceiling membrane and obviously needing a damper. They feel as long as the duct is firecaulked at the plate line and does not penetrate the ceiling a damper is not needed. Is this acceptable? How do other jurisdictions handle bathroom fans in rated ceilings? How about dryer exhaust ducts? A dryer duct goes into a non-rated wall up through the top plates, into the floor/ceiling cavity and outside. As long as the duct is the proper material and they firecaulk at the plate line is this acceptable? Thanks for any advice. Its been along time since we've seen stacked apartments and I'm a bit rusty.

 

[fatboy]

It's what we have accepted in the past, as long as the fire-stopping assembly matches the actual installation.

 

[peach]

look at IBC Section 716.6.1 (which of course sends you to 100 different code sections); you may be ok. (I'm just too lazy to look)

 

[FredK]

I agree with fatboy and peach. Have them find the acceptable ul design and add that to the plans.

I perfer that that detail gets on the mech and/or elect pages to prevent the Polish slap on the forehead in the field when one asks for why it doesn't match any "approved" detail. (Wonder how I know that will be the next question.)

 

[peach]

there used to be an exception for exhaust ducts.. I'm just too lazy to look to see if it's still there. Adopted code version would be helpful.

 

[Architect1281]

BUILD the Rated Assembly and the place the fan and duct in a drop soffit run to exterior wall

same for dryer vents and kitchen exhaust

you cannot rate or damper an exhaust duct unless its in a shaft assembly

it requires a little (VERY LITTLE) forethought and planning

anything more than mechanicals by others can predict the problem

some builders have to learn to bring some type x gyp to the jobsite before the drywall sub shows up

 

[Builder Bob]

The Bathroom wall may not be a fire resistant rated wall as only the walls seperating the dwelling units are required to be rated - hoever, alot of people use this exception #3 because the air exhaust duct does not constitute an air register in a fire rated wall. the code is really silent in this aspect.

The results of seeing residential fires for 30 years really indicates a less likely fire extension from the fan in the wall than in the ceiling. Just obersvations from riding the big red truck for a number of years.

The code section are from the 2006 ----- someday I hope to be in the newer edition of the I-codes.

716.5.4 Fire partitions. Ducts and air transfer openings

that penetrate fire partitions shall be protected with listed

fire dampers installed in accordance with their listing.

Exceptions: In occupancies other than Group H, fire

dampers are not required where any of the following

apply:

1. The partitions are tenant separation or corridor

walls in buildings equipped throughout with an

automatic sprinkler system in accordance with

Section 903.3.1.1 or 903.3.1.2 and the duct is protected

as a through penetration in accordance with

Section 712.

2. Tenant partitions in covered mall buildings where

the walls are not required by provisions elsewhere

in the code to extend to the underside of the floor or

roof deck above.

3. The duct system is constructed of approved materials

in accordance with the International Mechanical

Code and the duct penetrating the wall

complies with all of the following requirements:

3.1. The duct shall not exceed 100 square

inches (0.06 m2).

3.2. The duct shall be constructed of steel a

minimum of 0.0217 inch (0.55 mm) in

thickness.

3.3. The duct shall not have openings that communicate

the corridor with adjacent spaces

or rooms.

3.4. The duct shall be installed above a ceiling.

3.5. The duct shall not terminate at a wall register

in the fire-resistance-rated wall.

3.6. A minimum 12-inch-long (305 mm) by

0.060-inch-thick (1.52 mm) steel sleeve

shall be centered in each duct opening. The

sleeve shall be secured to both sides of the

wall and all four sides of the sleeve with

minimum 11/2-inch by 11/2-inch by

0.060-inch (38mmby 38mmby 1.52 mm)

steel retaining angles. The retaining angles

shall be secured to the sleeve and the wall

with No. 10 (M5) screws. The annular

space between the steel sleeve and the wall

opening shall be filled with mineral wool

 

[ndtolearn]

I apoligize, we using the 2009 I-codes. I know we've accepted bathfans installed this way before but couldn't put my finger on a code section to allow it. Like Peach said, it's one those times where the code sends you in circles to different sections. By the time I get back to where I started I'm totally confused. I guess I'll hang my hat on 713.4.1.2 and move on. Thanks again, its always nice to bounce things off this group to get another perspective.

 

[ccclove499]

I have the same question! I'm going to try to replace my own bathroom fans. If you knew me, you would question this decision. Regardless, I want to try to do it myself. Can someone suggest where to get a replacement fan and how to install it? Thanks for the help!