HVAC Ducts through 2hr Horizontal Assembly - 4 unit, 2 stacked units.

[stefana85]

Hello, we permitted a 4 units, 2 and 2 stacked on top, in Cleveland OH. We have approved MEP drawings - see attached but I am not longer confident they are optimal:

1. Building commissioner is asking us to make all floor ceiling assemblies 2 hr rated - ok fine
2. HVAC ducts to second floor will extend from basement, through 1st floor walls, and provide air to second floor. - they will receive 1.5 hr rated dampers (for 3hr max assembly penetrations per 717.3.2.1 Fire Damper Ratings).
3. I need help confirming this is acceptable by ICC and OBC 717.6.1 Through Penetrations - a duct that penetrates a fire resistance floor clg assembly that connects not more than two stories. Is the duct not connecting more than two stories or is the assembly not connecting more than two stories??? I chose to read it as assembly not connecting more than two stories - so we can run our ducts through walls of both 1st and 2nd units with dampers.
4. We only have 2 occupied levels over not occupied basement so shaft is not necessary.

Any other thoughts or clarifications - would love to hear.

Thank you all

717.6.1 Through Penetrations​

Amendment
In occupancies other than Groups I-2 and I-3, a duct constructed of approved materials in accordance with the 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 714.4. For air transfer openings, see Section 712.1.9.

 

[Yankee Chronicler]

Why does the commissioner want a 2-hour rating when Table 508.4 doesn't require any rating? Footnote a sends us to Section 420, and section 420.3 in turn sends us to section 711. I see nothing in section 711 to require any rating greater than the "Not Required" found in Table 508.4.

 

[stefana85]

Why does the commissioner want a 2-hour rating when Table 508.4 doesn't require any rating? Footnote a sends us to Section 420, and section 420.3 in turn sends us to section 711. I see nothing in section 711 to require any rating greater than the "Not Required" found in Table 508.4.

It is not logical nor code based. We're in the Residential Ohio Building Code btw. The commissioner refuses to have a discussion about it and wouldn't let us move forward otherwise (or he would have made me put a 2hr separation wall in a one exit only basement!). We need to get building. Regardless ... I would still like guidance on the duct penetration restrictions for 2hr floor assemblies in a 2 level over basement

 

[Yankee Chronicler]

Four dwelling units, two over two? How is that in the Residential Code?

 

[steveray]

Four dwelling units, two over two? How is that in the Residential Code?

Because certain jurisdictions are rolling back safety so poor people can die in affordable housing....

 

[stefana85]

They treat this as townhouses, one on top of another with 1 hr separation between, separated from another one over one by a 2 hr rated wall, including roof fire resistance for 4 feet each side. Separate entrances of course. No sprinklers needed but high on fire rating. Check out Ohio Residential code 302.2 if you want to know more. I don't see how any of this is unsafe. The amount of unpermitted and non sprinkled or protected 4 or 6 or 12 units in Cleveland would amaze you, this "allowance" is way better. Also none of this is affordable housing, I work on affordable housing too, and in many instances quality control is way higher due to funding requirements.

 

[Yankee Chronicler]

They treat this as townhouses, one on top of another with 1 hr separation between, separated from another one over one by a 2 hr rated wall, including roof fire resistance for 4 feet each side.

Who is "they"? Whoever "they" are, this is frightening in its idiocy.

IRC 2021:

TOWNHOUSE. A building that contains three or more
attached townhouse units.

IRC 2021 Commentary on the definition:

A configuration of three or more single-family dwellings
attached together in a single structure constitutes
a townhouse if all of the following conditions exist:
1. Each unit extends vertically from the foundation
to the roof (townhouses cannot be stacked,
though two-family dwellings can be).
2. Each unit is open to the exterior on at least two
sides, providing some degree of independence
from other units.
3. The structure is not more than three stories in
height above grade plane.
4. Each unit must have independent egress to the
exterior.
A townhouse structure that does not meet all of the
preceding four criteria is regulated by the IBC, not the
IRC.
It should also be noted that townhouses within the
IRC must be separated by a wall or walls meeting
specific criteria. A townhouse structure could be built
with any number of attached units on the same lot, or it
could be developed such that a property line lies at
each common wall separating dwelling units (see the
definition for “Lot”).

 

[stefana85]

Who is "they"? Whoever "they" are, this is frightening in its idiocy.

IRC 2021:



IRC 2021 Commentary on the definition:

I gave you the code section above. This is an existing structure, we just legalized it for the available zoning and code. Anyway, this conversation is not helping resolve my question.

 

[Yankee Chronicler]

I gave you the code section above. This is an existing structure, we just legalized it for the available zoning and code. Anyway, this conversation is not helping resolve my question.

I'm not in Ohio. I just checked UpCodes, and unless they missed it entirely, it doesn't appear that Ohio adopted the IRC. UpCodes doesn't list an "Ohio Residential Code." Do you have a link? If not, please reproduce the section so we can all know what you're going by.

 

[klarenbeek]

Any ducts that start in the basement and go up to 2nd floor DO connect more than two stories: basement, 1st floor, 2nd floor is three stories. It doesn't matter if there are no openings onto the first floor. A shaft is required since you are going through two fire resistance floor/ceiling assemblies. See 2021 IMC section 607.6.1. Ducts that only go from the basement to first floor will only require a fire damper.