# Thermal barrier over foam plastic



## jwilly3879 (Feb 20, 2018)

How many are enforcing R316.4 IRC 2015?


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## Sleepy (Feb 20, 2018)

Hopefully everybody, the foam plastic thermal barrier requirement is not new and strikes me as fairly important. Note that R316.5 offers lots of exceptions.


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## jwilly3879 (Feb 20, 2018)

It came to my attention that some are allowing 3/4" V joint t+g  pine over spray foam.


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## fatboy (Feb 20, 2018)

That does not meet the definition of "wood structural panels"..........


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## TheCommish (Feb 21, 2018)

I do.   I also allow it to be coated with inducement  paint width supporting  documents,   bear width supporting  documents, cover with sheet rock or wood sheeting  not taped and tight board such as ship lap or T&G


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## mtlogcabin (Feb 21, 2018)

R316.5 is an exception to Ignition Barriers in an attic. The gypsum board ceiling meets the thermal barrier requirement separating the foam from the occupied space below.
 The 3/4" V joint t+g pine over spray foam does not meet the specific requirements of R316.4 since I doubt you can find where it has been tested to NFPA 275 requirements.


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## Sleepy (Feb 21, 2018)

The American Wood Council, publication DCA-1 has some information on flame spread and smoke developed for wood products, but it is for ASTM E84, not NFPA 275. 
Link: http://www.awc.org/pdf/codes-standards/publications/dca/AWC-DCA1-FlameSpreadPerformance-1706.pdf


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## Sifu (Feb 21, 2018)

Yes, has been and may always be a real thorn in the side of some of the encapsulated crawlspace and attic installations.


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## Francis Vineyard (Feb 21, 2018)

jwilly3879 said:


> It came to my attention that some are allowing 3/4" V joint t+g  pine over spray foam.


"In the 70s the Society of the Plastics Industry in cooperation with the foam plastics industry conducted testing of various products as thermal barriers over foam. 3/4" tongue and groove wood decking was one of the materials tested that passed the thermal barrier tests. However, it is not specifically listed in the national codes and I am not aware of recent tests on the product."
Ask Mason Knowles - SPF Consultant


*R316.5.2 Roofing.* The thermal barrier specified in Section R316.4 is not required when the foam plastic in a roof assembly or under a roof covering is installed in accordance with the code and the manufacturer’s installation instructions and is separated from the interior of the building by tongue-and-groove wood planks or wood structural panel sheathing in accordance with Section R803, not less than 15/32 inch thick bonded with exterior glue and identified as Exposure 1, with edges supported by blocking or tongue-and-groove joints or an equivalent material. The smoke-developed index for roof applications shall not be limited.

Does the above require wood planks that are typically 2 inches thick?


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## mtlogcabin (Feb 21, 2018)

The NFPA 275 test limits the average temperature rise to 250 degrees F for all the termocouples or 325 for a single thermocouple. Smoke development is not a part of the test that I could find


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## jwilly3879 (Feb 21, 2018)

Wood planks are typically 2" nominal. Boards are 1" nominal.

The roof assembly mentioned in 316.5.2 I understood to be on top of the rafters where the wood planks separate the foam from the interior. The foam is exterior.


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## tmurray (Feb 26, 2018)

We enforce the equivalent in our code here. When we first started enforcing it, we were the only ones, despite it being in the code as early as 1985. It certainly caused a big stir and contractors went to our town manager with complaints claiming it was a new requirement. When I showed the manager the 1985 code (literally year I was born) was when it was introduced, he fully backed us up. Other adjacent jurisdictions have also started strictly enforcing this requirement now too.


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## JBI (Feb 27, 2018)

All other R&D and history aside, you'd think the Station Nightclub disaster would be enough to change a few minds...
NYS has had requirements since the late 90's for the thermal barrier. ALL NYS jurisdictions outside of NYC are required to enforce these provisions.


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## tmurray (Feb 27, 2018)

JBI said:


> All other R&D and history aside, you'd think the Station Nightclub disaster would be enough to change a few minds...
> NYS has had requirements since the late 90's for the thermal barrier. ALL NYS jurisdictions outside of NYC are required to enforce these provisions.


We complain about teens taking risks because "it'll never happen to me", but we all do it. We just improve our risk reward assessment is the only real difference. When I asked other municipalities why they were not enforcing this provision I was told that in the application it is in, it is not a hazard. I asked what technical evidence they used to come to this conclusion. They had none. They were just risking tax payer money to save private contractors money. Let alone risking the lives of the building occupants and first responders. Sometimes, even we need to be ready to do an honest self assessment to ensure we have the public's best interest at heart.


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## jwilly3879 (Feb 27, 2018)

Apparently some are under the impression that v-groove pine is acceptable. I will be raising this question at the upcoming Code Conference next week.
The spray foam applicators fail to mention this and then the contractor doesn't include the thermal or ignition barriers where required in their bids.
Here in the Adirondacks the v-groove pine is widely used for the "Rustic" look. Add 3 or 4 coats of poly to the pine and the problem compounds.


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## Paul Sweet (Mar 5, 2018)

http://www.greenbuildingadvisor.com...mal-barriers-and-ignition-barriers-spray-foam


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## jwilly3879 (Mar 5, 2018)

Apparently there is a document floating around that came from NYSDOS that states 3/4" tight fitting tongue and groove is equivalent to a 15 minute thermal barrier. I have yet to see it though and have requested a copy from the CEO that told me about it.


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## Coder (Apr 25, 2018)

I have reluctantly let 3/4" T&G pine pass in lieu of 23/32 wood structural panels on one house. It was installed throughout the entire house. The owner installed it all unknowingly to me then begged for forgiveness so he didn't have to tear it all out. I fretted over it for days until I came up with a document from AWPA that helped me feel a bit more confident in my decision. Is it perfect? no. but will it suffice? I believe it will.


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## rogerpa (Apr 26, 2018)

Coder said:


> I have reluctantly let 3/4" T&G pine pass in lieu of 23/32 wood structural panels on one house. It was installed throughout the entire house. The owner installed it all unknowingly to me then begged for forgiveness so he didn't have to tear it all out. I fretted over it for days until I came up with a document from AWPA that helped me feel a bit more confident in my decision. Is it perfect? no. but will it suffice? I believe it will.


Link?


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## Builder Bob (Jul 17, 2018)

NDS...


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