I encountered this on a new-construction inspection. Air handler in a closet with round, flexible ductwork penetrating the ceiling. Large gaps around the penetration. Some of the gap was filled with non-fire rated expanding foam.
How should this be properly installed? This kind of ductwork would burn or melt within seconds, rendering any firestopping irrelevant.
Any suggestions on how to call this out? I’m unsure of what the local codes require.
Since you local inspector knows the codes, what was his/her thought?
Well, getting through to one of them is a challenge. They are overwhelmed with work (it’s an overheated market here) and it’s nearly impossible to get hold of one unless they happen to be in the office when you call.
The builder’s response is generally “well, the local AHJ passed it so that’s all I care about”.
I’m more interested in the general practices called out by the IRC than what is locally required.
The question is really why flexible ductwork is permitted to pass through attic ceilings at all.
Plastic pipe goes through ceilings and walls. No fire rating on that stuff.
That’s a great point.
When they fire stop it’s more about preventing the air movement. The draft feeds the fire.
I recommended that the gaps be sealed and the area covered with insulation.
I hope that’s enough.
That’s perfect.
Thanks, everyone.
This is coming from an interior closet?
Is the utility closet sealed from the interior? If so, it is the fire stop.
What is the fire spread rating for flex duct? The duct must be metal if you need to seal the opening. Flex won’t cut it.
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BUILDING CODE REQUIREMENTS
FOR FIREBLOCKS
Prepared for
Don Holmes
Marketing Development Manager for Fire Protection Products
3M Company
by
Vickie J. Lovell
Building Code Consultant
InterCode Incorporated
December, 2003
The 2003 International Building Code (IBC) and 2003 International Residential Code (IRC)*
have established a means by which fire spread can be controlled within void spaces created
within wood framed assemblies: fireblocking.
During a fire, flame and heated products of combustion can spread via paths of least resistance.
Certain assemblies, particularly wood frame assemblies, result in concealed voids or cavities
within walls, ceilings and attics, which not only affect the spread of fire, but also make
suppression more difficult.
Fireblocking involves the use of field-installed building materials to prevent the movement of
undetected flames and gases to other areas through such concealed spaces. Although such
materials are not required to be tested for fire resistance, they are to be installed to slow fire
migration, and to contain a fire until it can be suppressed.
Fireblocks should not be confused with firestops. Firestops are required by the codes when a
higher degree of fire protection is required, particularly when penetrations through fire resistance
rated assemblies are to be protected with a specific assemblage of materials that have been tested
under severe fire conditions for a prescribed period of time. Unlike fireblocks, the purpose of a
firestop is to prevent the spread of fire from one compartment to another through service and
utility openings in floors, ceilings, roofs, and walls.
Fireblocks are required between floors, between a top story and a roof or attic space, in furred
spaces or the cavities between studs in wall assemblies, at connections between horizontal and
vertical spaces created in floor joists or trusses, soffits, drop or cove ceilings, combustible
exterior wall finishes and architectural elements, and at openings for pipes, vents, ducts,
chimneys, and fireplaces.
Fireblocks conform to innumerable configurations, depending on the dimensions and location of
the concealed space. Section 717 of the IBC is a dedicated section that provides the description of
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concealed spaces and fireblocking. Section 717.2.1 identifies the materials that are acceptable for
use as fireblocks. Fireblocks can be constructed of materials such as 2 inch nominal lumber,
structural wood panels, gypsum board, cement fiber board for larger fireblock, and batts or
blankets of mineral wool or glass fiber, loose fill insulation, and caulks, sealants, and putties for
smaller fireblocks. Similar text appears in the IRC.
Frequently, and inevitably, pipes, vents, ducts, and similar items penetrate fireblocks. The IBC
requires that the integrity of the fireblock be maintained in 717.2.1. This may be accomplished by
using an sealant, caulk or putty as permitted by 717.2.5. Such materials are required to be
approved for such use, and may be either combustible and noncombustible per the specific code
section and application. The use of a noncombustible sealant would address both conditions
where either combustible or noncombustible are required, but not vice versa. Therefore, a
noncombustible material would serve a broader range of uses than a combustible sealant, caulk or
putty. (Noncombustibility shall be determined by testing to ASTM E 136 per other sections of the
code).
All chimneys and fireplaces are required to be fireblocked by the code. Factory-built chimneys
and fireplaces are required to be fireblocked by the code, but are also required to be tested in
accordance with UL 103 and 127. Those test methods contain specific information pertaining to
fireblocking beyond the code requirements.
As a side bar, the IBC also requires the use of such noncombustible sealants in other locations
that are not related to fireblocks, but serve a similar purpose, such as small metallic membrane
penetrations within certain size restrictions in section 712.3.2, exceptions 1.3 and 2.2 In
penetrations of non-fire resistance rated assemblies, the IBC permits both combustible and
noncombustible sealants to be used to limit the migration of fire and the products of combustion.
The sealants used to protect noncombustible penetrations that connect not more than three stories
in section 712.4.3.1 are required to be noncombustible. 712.4.3.2 permits any approved sealant on
any type of penetration provided that the penetration does not connect more than two stories.
In all building codes, the designs and location for fireblocking are required to be indicated on the
construction documents, and are subject to inspection before occupancy in new construction.
Your local code may or may not adopt this code. You need to check if your going to try to enforce it.
The fire rating of PVC is a lot more than flex duct…
What is the fire rating? Last I heard it’s a combustible material but hey I’m willing to learn new things. ASTME E 136?
The fire rating of the building component it passes through is what the fire rating of the duct must be.
The fire rating of a garage barrier is higher than the interior of the house partitions. Therefore 24ga metal duct or 5/8ths Sheetrock to protect the duct is required.
So I ask what the fire rating of the utility room/closet is. The HVAC can’t just be out in the room. If the closet has a 1 hr rating, it is protecting the flex duct penetration.
If this is too complicated to hold a conversation with the builder, maybe you should not have that conversation. As he said the AHJ allowed it and you have no authority above that.
Some things to consider:
ASTM/UL 181
4.1.2.4Air connectors shall not pass through any wall, partition, or enclosure of a vertical shaft that is required to have a fire-resistance rating of 1 hour or more.
4.1.1.1.5
A Class 0 or Class 1 rigid or flexible air duct shall not be used in an air duct containing air at a temperature in excess of 121°C (250°F).
4.2.2 Duct Openings.
In buildings where vertical openings are required to be enclosed by walls or partitions having a fire resistance rating, openings in the enclosures for connections to vertical ducts carrying return air from more than one story shall be protected by approved fire dampers in such openings.
4.3.4 Protection of Vertical Ducts.
Where vertical ducts are installed within closets or rooms, they shall be enclosed with materials equivalent to those used in the closet or room construction. (See 5.1.3.) 4.1.2.4
Air connectors shall not pass through any wall, partition, or enclosure of a vertical shaft that is required to have a fire-resistance rating of 1 hour or more.
4.1.1.1.5
A Class 0 or Class 1 rigid or flexible air duct shall not be used in an air duct containing air at a temperature in excess of 121°C (250°F).
4.2.2 Duct Openings.
In buildings where vertical openings are required to be enclosed by walls or partitions having a fire resistance rating, openings in the enclosures for connections to vertical ducts carrying return air from more than one story shall be protected by approved fire dampers in such openings.
4.3.4 Protection of Vertical Ducts.
Where vertical ducts are installed within closets or rooms, they shall be enclosed with materials equivalent to those used in the closet or room construction. (See 5.1.3.)
