Thread: Ducts thru attic floor

I was wondering if anyone has an image of a fireblock for flex ducts?

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Originally Posted by Marc M

I was wondering if anyone has an image of a fireblock for flex ducts?

Marc,

I believe what you are looking for is a draft stop. I probably have one somewhere in the thousands of photos that I have taken, but I have not been able to find one tonight.

Tell you what, how about I stick all of my photos onto a DVD and mail them off to you so you can sift through them.

If no one posts a photo by tomorrow, I will do a bit more searching.

That looks like a flexible air connector which is limited to 14 foot in length and would need to be sleeved at any floor or wall penetration. they sell a duct would be secured to a metal sheet stock with the round metal sleeve through it, and then the flexi attached to both sides. Theres no way you can maintain the integrity of draft stopping in the penetration that you observed.

Originally Posted by Marc M

I was wondering if anyone has an image of a fireblock for flex ducts?

It sounds like if you follow this code section you will be ok.

R602.8.1.1 Unfaced fiberglass.

Unfaced fiberglass batt
insulation used as fireblocking shall fill the entire cross
section of the wall cavity to a minimum height of 16
inches (406 mm) measured vertically. When piping, conduit
or similar obstructions are encountered, the insulation

shall be packed tightly around the obstruction.

you actually want the Mechanical code section

603.6.2.2- Connector penetration limitations.
"Flexible air connectors shall not pass through any wall,floor, or ceiling"

I agree with Josheph and find that, although James advice is true, it can't be applied in this situation because of the collapsibility of the duct. His reference is associated with hard goods like piping or conduit.

The only way to do it is with a sheet metal flange at attic floor and lower level lid that the flex connects to.

Originally Posted by Joseph Ehrhardt

you actually want the Mechanical code section

603.6.2.2- Connector penetration limitations.
"Flexible air connectors shall not pass through any wall,floor, or
ceiling"

Here is what the manufactures installation instructions says:

a.

Shall not be used for vertical risers serving

more than two stories in height.

Originally Posted by Mitchell Toelle

I agree with Josheph and find that, although James advice is true, it can't be applied in this situation because of the collapsibility of the duct. His reference is associated with hard goods like piping or conduit.

The only way to do it is with a sheet metal flange at attic floor and lower level lid that the flex connects to.

In the area I work in the AHJ allows you to fire-caulk around the flexible duct where it goes through a floor or ceiling.

Originally Posted by Gunnar Alquist

Marc,

I believe what you are looking for is a draft stop. I probably have one somewhere in the thousands of photos that I have taken, but I have not been able to find one tonight.

Tell you what, how about I stick all of my photos onto a DVD and mail them off to you so you can sift through them.

If no one posts a photo by tomorrow, I will do a bit more searching.

GA, go thru them first, wouldnt want to get anything questionable...

I agree, metal flange or fiberglass batt around the opening would make sense. Here where I live the attic floor is the ceilings drywall. I have seen metal collars like the ones which pass thru seperation walls, but never in an attic. I would, however, expect to see that (collar) in this specific situation, especially when the duct passes thru the interior walls to the first floor level.

I've seen this 1000's of times without a draft-stop (wouldn it help much in a fire as the duct melts within seconds?) which is the same as saying I've never seen it provided draft-stopping. The photo with the OSB penetration is interesting as I've never seen a paneled ceiling when viewed from the attic. Yes, it makes sense that vertical ducting runs should be metal and draft-stopped. It even makes sense to draft stop a duct chase to prevent pressure differentials within interstitial areas from moving through the building. But...I've never seen it.

Originally Posted by Marc Morin

I've seen this 1000's of times without a draft-stop (wouldn it help much in a fire as the duct melts within seconds?) which is the same as saying I've never seen it provided draft-stopping. The photo with the OSB penetration is interesting as I've never seen a paneled ceiling when viewed from the attic. Yes, it makes sense that vertical ducting runs should be metal and draft-stopped. It even makes sense to draft stop a duct chase to prevent pressure differentials within interstitial areas from moving through the building. But...I've never seen it.

The picture of the OSB penetration was taken on the second floor where the ducts go to the first floor ceiling. It was done the same where the ducts entered the attic but I don't have a picture of that to share. There was two gas furnaces in the attic....one for each level.

If you have seen it done wrong a 1000 times I hope you wrote it up a 1000 times.

Originally Posted by Marc Morin

I've seen this 1000's of times without a draft-stop (wouldn it help much in a fire as the duct melts within seconds?) which is the same as saying I've never seen it provided draft-stopping. The photo with the OSB penetration is interesting as I've never seen a paneled ceiling when viewed from the attic. Yes, it makes sense that vertical ducting runs should be metal and draft-stopped. It even makes sense to draft stop a duct chase to prevent pressure differentials within interstitial areas from moving through the building. But...I've never seen it.

Same here...thousands of times. I have wrote it up when I see it but I have been referring to it as " firestopping needed", I suppose fireblocking may have worked as well.. I also agree with the fact that the duct will melt quickly. I assume the draft stop may decrease the availability of oxygen via drafting to further spread flame?? I'm not a fire man so Im not totally familiar with fire or how it works.

Some of the post seem to be confusing Flexible Air Ducts and Flexible Air Connectors. The code is a bit different for each. Here is a link that explains the differences. You will notice that it is flexible connectors that can not penetrate floors, walls, and ceilings.....not flexible air ducts.

http://www.hartandcooley.com/Librari...?download=true

That looks like a flexible duct to me.

When going through the ceiling or floor it needs to be firestopped around it. That basically means that if you cut a suitably small enough hole through the drywall and fit the flexible duct through it, and the duct insulation was not crushed, that would be firestopped ... except that we know that would also not be tightly fitting around the duct, meaning it may not be effectively firestopped.

If the hole were cut smaller, the duct insulation would be crushed, and that would not be good either, nor would that be allowed.

The "best" solution is to use duct board to penetrate through the ceiling, then attach the flexible duct to the duct board above and below the ceiling - but this is RARELY done - and I do mean rarely done, as in asking for a rare steak and they walk the cow up and cut a piece off for you right there in the restaurant - how ofter does that happen?

Okay, let's go back to the first part about cutting the hole and how tight that hole needs to be around the flexible duct - how tightly fitting is the fireblocking installed (when installed) around metal chimneys and vents? There is a slight gap around the metal chimney and between that and the fireblock piece.

Sooo, let's start here: (bold and underlining are mine)
- FIREBLOCKING.Building materials installed to resist the free passage of flame to other areas of the building through concealed spaces.

Then we go to:
- R602.8 Fireblocking required. Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space. Fireblocking shall be provided in wood-frame construction in the following locations.
- - 1. In concealed spaces of stud walls and partitions, including furred spaces and parallel rows of studs or staggered studs; as follows:

- - - 1.1. Vertically at the ceiling and floor levels.
- - - 1.2. Horizontally at intervals not exceeding 10 feet (3048 mm).
- - 2

. At all interconnections between concealed vertical and horizontal spaces such as occur at soffits, drop ceilings and cove ceilings.
- - 3. In concealed spaces between stair stringers at the top and bottom of the run. Enclosed spaces under stairs shall comply with Section R311.2.2.
- - 4. At openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion.
- - 5. For the fireblocking of chimneys and fireplaces, see Section R1003.19.
- - 6. Fireblocking of cornices of a two-family dwelling is required at the line of dwelling unit separation.
- - R602.8.1 Materials. Except as provided in Section R602.8, Item 4, fireblocking shall consist of 2-inch (51 mm) nominal lumber, or two thicknesses of 1-inch (25.4 mm) nominal lumber with broken lap joints, or one thickness of 23/32-inch (19.8 mm) wood structural panels with joints backed by 23/32-inch (19.8 mm)wood structural panels or one thickness of 3/4-inch (19.1 mm) particleboard with joints backed by 3/4-inch (19.1 mm) particleboard, 1/2-inch (12.7 mm) gypsum board, or 1/4-inch (6.4 mm) cement-based millboard. Batts or blankets of mineral wool or glass fiber or other approved materials installed in such a manner as to be securely retained in place shall be permitted as an acceptable fire block. Batts or blankets of mineral or glass fiber or other approved nonrigid materials shall be permitted for compliance with the 10 foot horizontal fireblocking in walls constructed using parallel rows of studs or staggered studs. Loose-fill insulation material shall not be used as a fire block unless specifically tested in the form and manner intended for use to demonstrate its ability to remain in place and to retard the spread of fire and hot gases.
- - - R602.8.1.1 Unfaced fiberglass. Unfaced fiberglass batt insulation used as fireblocking shall fill the entire cross section of the wall cavity to a minimum height of 16 inches (406 mm) measured vertically. When piping, conduit or similar obstructions are encountered, the insulation shall be packed tightly around the obstruction.
- - - R602.8.1.2 Fireblocking integrity. The integrity of all fireblocks shall be maintained.

First a question: Is that a concealed area below, such as an enclosed chase?

Second, regardless of the answer to the first question above , it is a duct going through the ceiling, which looks to be drywall, and drywall is an "approved material" for fireblocking.

How does it have to be installed?
- "4. At openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion."

If the drywall was/is snug to the gypsum board, it may well satisfy "to resist the free passage of flame". After all, that is not required to be fire-resistance rated nor is it required to be a firestopping material or firestopping system.

The drywall was not very snug up against the duct as pictured. It was a chase to the lower floor.

Originally Posted by James Duffin

Some of the post seem to be confusing Flexible Air Ducts and Flexible Air Connectors. The code is a bit different for each. Here is a link that explains the differences. You will notice that it is flexible connectors that can not penetrate floors, walls, and ceilings.....not flexible air ducts.

http://www.hartandcooley.com/Librari...?download=true

I looked at that info, (BTW thanks) and it looks like connectors are somewhat rigid, this duct was flexible.

I have seen a drywalled first-floor-to-3rd-floor column used for air ducting and other miscellaneous communications/network wiring. In this case, this was an open column with no attempt to put in any kind of stops. What are your comments about this application?

Also, in another home, the AC/airhandler had been moved from the HVAC closet in the one-story home to the attic. The owner required that there be no large return register installed in the hallway ceiling. So, the contractor ran a 24" flex duct down from the attic through a drywalled and sealed column that went from the top of the return air plenum to the ceiling. At the top of the air return plenum (used to be under the updraft air handler), he attached the ducting to a collar to the plywood that separated the plenum from the column. The building inspector would not sign off the installation until the drywall was finished and sealed. Other than the questions raised here, this seems to make sense and is OK. Comments?