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Structural Insulated Panels(SIPs) in Type III-B Ext Wall

R

retire09

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Feb 19, 2010
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Alaska
I have a plan to review for a 2 story B occupancy building of Type III-B construction.

The exterior walls are all structurally non bearing and due to fire separation distance are not required to be rated.

Type III construction requires exterior walls to be of noncombustible materials.

The architect wants to use SIPs with FRT panels on each side as part of the wall assembly.

All materials in the wall are allowed as noncombustible except the SIPs and the FRT panels are within the wall with GYP on the inside and metal siding on the outside.

Since the wall is unrated and nonbearing, will this wall assembly still meet the intent of the code for type III construction as noncombustible?
 
IF FRT is Fire Resistant Treated the answer is no it is still combustible

Last time I checked (about 3 years ago) the SIPs manufacture could not get the fire treated panels to adhere to the styrofoam
 
The insulation in the SIP's would need to be non-combustible, which is unlikely.

I would send the architect's plans to the state board.
 
I was trying to find a UL design no. for a wood framed wall with spray foam between studs. It turned out that you could only get a rating for a wall assembly with metal studs....

I'm with brudgers, the insulation is too combustible otherwise they would have had it tested and passed for a UL design no.
 
Does it have to be a III-B? IBC 602.1.1 Minimum requirements "a building or portion thereof shall not be required to confom to the details of a type of construction higher than that type which meets the minimum requirements based on occupancy even though certain features of such building actually conform to a higher type of construction."

Can it be a V-B building?

If it can, then it is according to the Code.

The designer/owner frequently classifies buildings as a higher "type" of construction for various reasons, including insurance/bonding; the code doesn't have that same restriction.
 
I would start with Peach's approach. It does not work as IIIB, but maybe a type VB. But that is the Architect's job to present to you.
 
retire09 said:
Look at IBC 2603.5 in the 2009 IBC. How does that apply?
Click to expand...
It allows foam plastic inside an exterior wall

Your OP was asking about a Type III building which is required to have 2 hour ressitance on the bearing walls. Foam would be acceptable in a non combustible tested assembly

2603.5.1 Fire-resistance-rated walls.

Where the wall is required to have a fire-resistance rating, data based on tests conducted in accordance with ASTM E 119 or UL 263 shall be provided to substantiate that the fire-resistance rating is maintained
 
Fire retardant treated FRT plywood, while it is still a combustible material, has been chemically treated to provide a lower flame-spread rate than un-treated plywood used in building construction
 
IIIB is used as a "catch all" classification for the lazy architects.

We approve combustible rated construction all the time.

Steel isn't fire rated (which is why it needs to be protected), but it's non combustible (it melts instead).

Read the IBC commentary; it's explanatory information which says "altought FRTW does not meet the specifications of the code as a noncombustible material, it is permitted as a substitute for noncombustible materials in exterior wall assemblies of type III construction... FRTW is required to comply with the provisions in Section 2303.2
 
The issue with a SIP is that the insulation is often combustible.

Maybe you didn't do your homework?
 
The foam is combustible but IBC 2603.5 specifically allows it in type III construction.

Once again, the walls are non rated due to fire distance and non bearing.

I would say the foam is allowed as long as it is separated from the interior of the building by a thermal barrier.

So exterior walls of type III construction are noncombustible except as allowed by 2605.3.

Is this a mistake in the code?
 
retire09 said:
The foam is combustible but IBC 2603.5 specifically allows it in type III construction. Once again, the walls are non rated due to fire distance and non bearing. I would say the foam is allowed as long as it is separated from the interior of the building by a thermal barrier. So exterior walls of type III construction are noncombustible except as allowed by 2605.3. Is this a mistake in the code?
Click to expand...
Umm...if the building is a cold storage building per 2603.5 and the assembly has been tested per 2603.5.7 and labeled per 2603.5.6. and the typical insulation in a SIP is going to have trouble meeting the flame spread and smoke developed ratings in 2603.5.4.

There probably are specialized products out there.

But the average SIPS shop may not have them.
 
Here is a SIP that is fire rated as tested per ANSI/UL 263:
BXUV.U532
UL Design No. U532

Polystyrene core with 5/8" gypsum on each side. Approved since August 8, 2001.
 
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