# foam and foam board flammability



## AGWhitehouse

Under current codes, foam needs to be covered with an ignition barrier within attics and crawlspaces. Below is a code exerpt pertaining to the thermal barrier requirements.

*2009 IRC excerpts:

R316.5.3 Attics.* The thermal barrier specified in Section R316.4 is not required where all of the following apply:

1) Attic access is required by Section R807.1.

2) The space is entered only for purposes of repairs or maintenance.

3) The foam plastic insulation is protected against ignition using one of the following ignition barrier materials:
3.1) 1-1/2 inches (38mm) mineral fiber insulation
3.2) 1/4 inch (6.4mm) thick wood structural panels
3.3) 3/8 inch (9.5mm) particleboard
3.4) 1/4 inch(6.4mm) hardboard
3.5) 3/8 inch (9.5mm) gypsum board
3.6) Corrosion-resistant steel having a base metal thickness of 0.016 inch (0.406mm)

The above ignition barrier is not required where the foam plastic insulation has been tested in accordance with Section R316.6.

*R316.6 Specific Approval.* Foam plastic not meeting the requirements of Sections R316.3 through R316.5 shall be specifically approved on the basis of one of the following approved tests: NFPA 286 with the acceptance criteria of Section R302.9.4, FM4880, UL 723, UL 1040 or UL 1715, or fire tests related to actual end-use configurations. The specific approval shall be based on the actual end use configuration and shall be performed on the finished foam plastic assembly in the maximum thickness intended for use. Assemblies tested shall include seams, joints and other typical details used in the installation of the assembly and shall be tested in the manner intended for use.


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## bubbler

Would the joist bay be considered part of the attic if I have wood planks down for the floors?

Basically I will have foam board used under the knee wall in the joist bay, one side is exposed only to the joist bay between first and second floors. The other side is exposed to the joist bay in the knee wall attic, which will be filled with cellulose. The joists are covered by 1x12 planks.

So the foam is technically not exposed in the attic space itself, but rather in a joist bay.

As for the Great Stuff, using that stuff for air sealing which is then covered by FG insulation would NOT be OK?


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## AGWhitehouse

The foam is allowed within a sealed ceiling joist or stud bay. As long as the foam is covered, by a minimum of the coverings noted, so when the job is done you cannot see any foam from anywhere within the attic space.


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## federer

if foam is being sprayed to achieve 8.5inches, this means it should be done in 2 separate layers to prevent fire?


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## bubbler

federer said:


> if foam is being sprayed to achieve 8.5inches, this means it should be done in 2 separate layers to prevent fire?


See the link in my post here--


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## bubbler

AGWhitehouse said:


> The foam is allowed within a sealed ceiling joist or stud bay. As long as the foam is covered, by a minimum of the coverings noted, so when the job is done you cannot see any foam from anywhere within the attic space.


I decided to use wood. I didn't need the insulation value (since it will have blown cellulose against it... and I also found that the joist bays were almost spot on at 14.5" wide and 8" deep.


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## AGWhitehouse

federer said:


> if foam is being sprayed to achieve 8.5inches, this means it should be done in 2 separate layers to prevent fire?


If it's closed cell, 4 layers in 2" maximum lifts...


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## Gary in WA

Sounds as if you already had it done, tell us how and what materials…..

For others interested in Formular 250, etc. foamboard in an attic, if you meet certain conditions, and present your inspector with a copy of this beforehand- you may be good to go without a covering ignition barrier: 4.2.1--- http://commercial.owenscorning.com/assets/0/144/172/174/5deb06d2-43b4-44b2-b4ec-20579af27e5d.pdf

It’s from the same people that write the “I” codes: IRC, etc.: http://www.ncfi.com/Insulation/uploads/Evaluation%20Reports,%20Acceptence%20Criteria%20and%20the%20Building%20Codes%20SF0608L.pdf

If they don’t buy that you can install some J.M Spider fiberglass batt insulation over it for an ignition barrier: 
http://docs.google.com/viewer?a=v&q...-uEOOx&sig=AHIEtbTldLgFaTlaOxVH0hR298hcCu6EbQ. 



Gary


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## bubbler

GBR in WA said:


> Sounds as if you already had it done, tell us how and what materials…..


If you're talking to me....

I decided to abandon the plan to use the Foamular 250 boards, I got worried about the potential for acrid smoke in a fire, etc--though granted there is only the equiv. of a single 4'x8' board that would have been spread around.

What I did was to buy a 4x8 sheet of 1/2" BC plywood, I cut it into strips 8" thick x 8' long, then cut that into 14.5" chunks (so I had 8"x14.5" rectangles). 

I was able to wedge 80% of them into place w/ no fastners, a few were a little too large so I cut them down and a few were a little too loose so I drove four 1-5/8" sheet rock screws in to the joist to act as a back stop. 

I sprayed the perimeter of each board with Great Stuff Gap & Crack sealer. The purpose of these boards is to act as an air seal under my knee wall and also as a physical stop for blown cellulose insulation to be installed later.

In hind sight the foamular would probably be fine to use in that situation, it's protected from ignition on the attic side by the cellulose and on the joist side it's surrounded by either drywall (ceiling of first floor), 2x8 wood (joists) or plywood (subfloor of second floor).

I'm not sure what to do w/ the foam I bought. I'm considering putting it against my rim joists and then covering the face w/ R13 FG as an "ignition barrier". My opinion is that it's probably less safe in that location then in the joists, but it will serve a better purpose as an air barrier there.


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## AGWhitehouse

GBR in WA said:


> you can install some J.M Spider fiberglass batt insulation over it for an ignition barrier:


For the third time, fiberglass is not an approved ignition barrier...


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## bubbler

AGWhitehouse said:


> For the third time, fiberglass is not an approved ignition barrier...


I didn't post that link, but I did read it, and according to JM it is usable as an ignition barrier...... 

It's the first line of linked app note "...can be used as an ignition barrier over SPF in vertical and overhead applications" ... goes on to specifically include conditioned attics and foam sheathed knee walls.

Now, maybe you believe they are incorrect in their read on the code (which would mean they are open to law suits), or maybe this is not just generic FG which is what you may be thinking of?


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## federer

this is what i mean there is like an argument to every side. it gets confusing!


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## AGWhitehouse

The code very specifically notes "mineral fiber". If that specific product meets the very specific available exceptions, then I appologize.

Point is, if you want to get around covering the foam with the very specific requirements noted in the code, go see the building official first and foremost. This code language was created for life safety issues as the foam burns FAST. You shouldn't mess around here, it could get you into a heap of trouble. Online chatrooms are no place to assume code modifications will be found acceptable.


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## bubbler

federer said:


> this is what i mean there is like an argument to every side. it gets confusing!


No kidding... and even the "pros" don't know everything. 

Part of my insulation quote includes adding foam to the access doors, this foam would be sitting on the attic side of the door... I saw what he brought, noticed a foil/silver face and thought "oh good, that my be an ignition barrier"... nope, written right on the front of the foil it says "THIS IS A FLAMMABLE PRODUCT AND MUST BE PROTECTED FROM FLAMES AND IGNITION SOURCES".


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## bubbler

AGWhitehouse said:


> foam burns FAST. You shouldn't mess around here, it could get you into a heap of trouble.


Absolutely agree here.

Anyone doubts this, go buy three items from a HW store:

A 2x4, a FG batt w/ paper, and a chunk of Foamular (or similar foam board).

Hold a match under each one and you'll see what a VAST difference there is in burn rate, and the smoke produced... foam is scary stuff in that regard.


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## federer

for me that begs the question- code says drywall alone is sufficient as barrier to foam. interesting


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## AGWhitehouse

federer said:


> for me that begs the question- code says drywall alone is sufficient as barrier to foam. interesting


That is plenty sufficient covering. The purpose of the ignition barrier is to delay the inevitable combustion of the product long enough to ensure that the building inhabitants can escape. Drywall is used extensively in fire rated wall assemblies and 2 layers of 5/8" type X is generally considered to give a 1-hour rating.


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## federer

oh ok cool. so that will give me enough time to grab some stuff before i leave!


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