1. ATTENTION returning members. If you are coming here from the old forum for the first time, you will need to reset you password. However, we had an email problem getting password reset links set out to a lot of the email addresses. That problem is temporarily rectified but IF you still have an issue, email me direct at info@thebuildingcodeforum.com and I will give you a temporary password.
    Dismiss Notice
  2. 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 clicking here: Upgrades
    Dismiss Notice

Dryer Duct in Multi-Family Wood Apartment Project Questions

Discussion in 'Commercial Building Codes' started by ETThompson1, Mar 6, 2019.

  1. ETThompson1

    ETThompson1 Supporter

    Joined:
    May 22, 2017
    Messages:
    106
    Likes Received:
    2
    Hi

    I've looked at several dryer exhaust threads but still not quite clear on the two issues I have on my project. Multifamily apartment/mixed-use, VB, 12.5k sf, full sprinkler. Ohio Building Code 2017, based on 2015 IBC.

    1. Can the dryer exhaust penetrate a rated wall? The walls are required to be rated for two reasons, either fire separation distance less than 10' (which means they are 1-hour rated from exterior as well as interior) or because some of them are part of an egress court. I know that the mechanical code (IMC) 504.2 says you cannot unless the duct is constructed of the right material (which we can do) and in compliance with the building code.

    IBC 705.10 tells me ducts in exterior FRR walls required to have opening protections shall comply with section 717. But the reference there (717.5.6) is circular, referring back to 705.10. But my reading anyway is I don't have to have opening protectives per 705.8 - we're under the percentage of required openings for that wall. Is that correct?

    2. Secondly, we had planned to run our dryer duct through the floor assembly (L528), based on input from our mechanical engineer. We are using a 14" depth, so we can't have dampers anyway (L528 requires 18" depth for using approved dampers). The concept was that since the dryer duct did not (and cannot) have dampers, this should be allowable. The dryer duct starts at a non-rated wall, turns vertically up into it, penetrates the top of the non-rated partition, and turns from vertical to horizontal laterally to head out (in a straight run) to the exterior facade. Am I right in thinking this should work, and without modifying the 14" depth?

    Thanks
     
  2. cda

    cda Sawhorse

    Joined:
    Oct 19, 2009
    Messages:
    15,463
    Likes Received:
    931
    Not an expert

    But I would say yes to both questions
     
  3. IJHumberson

    IJHumberson Sawhorse

    Joined:
    Oct 30, 2009
    Messages:
    85
    Likes Received:
    21
    With respect to Question #1, so long as your openings are less than 10% of the wall area (which they easily should be), it looks like you'd comply.

    With respect to Question #2, in the UL L528 Floor/Ceiling Assembly, the references are only to ceiling dampers (which is not what you'd have in a continuous duct), and it limits the use of such to the 18-inch deep assembly. Correct me if I'm wrong, but I'm not seeing any exemption in IBC or in the UL L528 listing criteria that would allow the unprotected penetration of a rated floor/ceiling assembly by a dryer exhaust duct, just because the floor/ceiling assembly is less than 18 inches in depth.
     
  4. ETThompson1

    ETThompson1 Supporter

    Joined:
    May 22, 2017
    Messages:
    106
    Likes Received:
    2
    Thanks for the response. Looking back at the reviewer's comments, I think I'm seeing the issue. She cites 717.6.1 and 717.6.3 which deal with through or membrane penetrations of a FRR floor/ceiling assembly. So maybe the issue isn't that we can't have the 14" depth (which would be prevented by having a damper, which we're not allowed anyway), but because we can't penetrate the membrane (or go through the assembly) without a damper. I thought, based on comments from my mech engineer, that there was an exception if we were coming up through the top of a partition wall (and therefore not penetrating the membrane?), but I'm not finding it.

    If not, could we use one of these methods? http://www.ncdoi.com/OSFM/Engineering_and_Codes/Documents/Interpretations4/2012%20Building/0716.6.2%20-%20Dryer%20Duct%20Rated%20Assembly%20Membrane%20Penetrations.pdf
     
  5. ETThompson1

    ETThompson1 Supporter

    Joined:
    May 22, 2017
    Messages:
    106
    Likes Received:
    2
    Update: spoke to my mechanical engineer, he apparently negotiated the approach to the dryer exhaust with the building official directly. It was not clear this is based on any code exception, but the concept is as I noted above - because the penetration comes through the top of the partition wall, she apparently does not consider it a membrane penetration, and therefore is good. My fingers are crossed that he is correct and there has not been a miscommunication...
     
  6. steveray

    steveray Sawhorse

    Joined:
    Nov 25, 2009
    Messages:
    6,163
    Likes Received:
    771
    Penetrating rated structure is probably not an issue (exterior wall)....Penetrating some sort of rated separation gets a little more sticky (floor/ceiling assembly).....
     
  7. ETThompson1

    ETThompson1 Supporter

    Joined:
    May 22, 2017
    Messages:
    106
    Likes Received:
    2
    Thanks - that's the conclusion I've come to. I hope the MEP is right and the floor/ceiling penetration works...
     
  8. cda

    cda Sawhorse

    Joined:
    Oct 19, 2009
    Messages:
    15,463
    Likes Received:
    931
  9. Yikes

    Yikes Gold Member

    Joined:
    Nov 2, 2009
    Messages:
    1,293
    Likes Received:
    127
    Msradell likes this.
  10. ADAguy

    ADAguy Sawhorse

    Joined:
    Sep 11, 2013
    Messages:
    2,863
    Likes Received:
    261
    You mention two (2) horizontal transitions from vertical, both become collection points for lint.
    Does the vent have a blower to suck the lint out?
     
  11. ETThompson1

    ETThompson1 Supporter

    Joined:
    May 22, 2017
    Messages:
    106
    Likes Received:
    2
    Not sure...I think so but will check w mechanical. But the bends factor into the limited length, so I think that already may be taken into account by the code...
     
  12. mtlogcabin

    mtlogcabin Sawhorse

    Joined:
    Oct 17, 2009
    Messages:
    7,058
    Likes Received:
    720
    2012 IMC
    504.3 Cleanout.
    Each vertical riser shall be provided with a means for cleanout.
     
  13. ADAguy

    ADAguy Sawhorse

    Joined:
    Sep 11, 2013
    Messages:
    2,863
    Likes Received:
    261
    Cleanout/outs must therefore be accessible?
     
  14. mtlogcabin

    mtlogcabin Sawhorse

    Joined:
    Oct 17, 2009
    Messages:
    7,058
    Likes Received:
    720
    No they do not have to be accessible to the handicapped. It can be simply moving the dryer out of the way and disconnecting the transition duct or an elbow where it changes from horizontal to vertical.
     
  15. steveray

    steveray Sawhorse

    Joined:
    Nov 25, 2009
    Messages:
    6,163
    Likes Received:
    771
    We don't really define "riser" in the IMC......would you use the IPC "one full story" guideline?
     
  16. ADAguy

    ADAguy Sawhorse

    Joined:
    Sep 11, 2013
    Messages:
    2,863
    Likes Received:
    261
    Wouldn't that be defined as any vertical element between direction transitions?
    If so and as previously noted above that there are multiple transitions then each vertical riser would require access to it, no?
     
  17. mtlogcabin

    mtlogcabin Sawhorse

    Joined:
    Oct 17, 2009
    Messages:
    7,058
    Likes Received:
    720
    No I would not. The term "riser" in the mechanical code is used 5 times to refer to grease and dryer ducts that "rise" either vertically or by offsets. The only time a distance is specified is a return air duct that serves two or more stories.
     
  18. ETThompson1

    ETThompson1 Supporter

    Joined:
    May 22, 2017
    Messages:
    106
    Likes Received:
    2
    I would hope my engineer knows this, but I will check. Thanks!
     
  19. rgrace

    rgrace Sawhorse

    Joined:
    Feb 18, 2010
    Messages:
    154
    Likes Received:
    30
    I believe the reference you are looking for is (2015) IBC 714.4.2 exception 7.

    Item 1 - I'm pretty certain there are no duct wraps out there that are listed for the combination of (1) clothes dryer exhaust duct and (2) use in lieu of a ceiling radiation damper
    Item 2 - Pretty much the same as item 1. Good luck with that too.
    Item 3 - Looks like a reasonable approach.
     
    tmurray likes this.
  20. mtlogcabin

    mtlogcabin Sawhorse

    Joined:
    Oct 17, 2009
    Messages:
    7,058
    Likes Received:
    720

Share This Page