# Is XPS Foam Toxic



## HomeSealed (Jan 3, 2008)

XPS is hazardous when burned/melted. Most building codes will call for it to be covered by sheetrock when installed in living spaces. There are some gray areas when you get into crawlspaces, attics, etc. I have found that different municipalities look at it in different ways, but generally speaking it needs to be covered if it is within the building envelope (ie: conditioned living space). For example, in a kneewall attic, if you have it on the back side of the kneewall it does not need to be covered. If you switch it up to the underside of the roof deck you do, because that is now conditioned space even if it is only used for starage and is separate from the regular "living space"... Make sense?

On the "best way to insulate", the answer to that question will vary depending on the application.


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## leungw (Apr 20, 2009)

When I did my basement, I put XPS on the concrete wall, then framed 2x4 in front of it. I was going to leave the wall cavities empty and just drywall. Inspector said I needed a fireblock directly in front of the XPS. I ended up adding fiberglass in all the wall cavities.


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## ryanmcl (Jan 7, 2013)

I was planning on taking my time and doing the basment over a 2yr period. Not sure what he menas when he says i need to cover with sheet rock "immediatly".


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## HomeSealed (Jan 3, 2008)

It does not need to be covered the same day, but you are not going to want leave it for two years either. It is a potential safety hazard, so just use some common sense. Either expedite the project to a couple months, or finish of one section at a time where you foam, then Sheetrock, foam, then Sheetrock.


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## AGWhitehouse (Jul 1, 2011)

HomeSealed said:


> For example, in a kneewall attic, if you have it on the back side of the kneewall it does not need to be covered.


This a potentially false statement as it is in potential direct conflict with section R316.5.3 Attics from the 2009 International Residential Code. It reads as follows: 

*R316.5.3 Attics.* The thermal barrier specified in Secion 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-inch-thick (38 mm) mineral fiber insulation
3.2 1/4-inch-thick (6.4 mm) wood structural panels
3.3 3/8-inch-thick (9.5 mm) particleboard
3.4 1/4-inch-thick (6.4 mm) hardboard
3.5 Corrosion-resistant steel having a base metal thickness of 0.016 inch (0.406 mm)

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

*R316.4 Thermal barrier.* _(essentially states all foam shall be seperated from the interior living space by 1/2" gypsum board)_
*R316.6 Specific approval.*_ (must meet NFPA 286 with the acceptance criteria of R302.9.4, FM4880, UL 723, UL 1040 or UL 1715.)_
*R807.1 Attic access.* _(essentially states attics over 30sq.ft. and 30" high shall have an access panel)_

My statement of "potentially" is because in areas where the IRC doesn't apply, the above may not apply and your statement could be correct if the AHJ agrees and approves. Also, if the purchased foam meets the specific approval criteria, it wouldn't need to be covered either. BUT, in any areas following standardized code systems (all of CT for sure) and installing standard XPS foam (no factory facings, coatings, etc.) that statement is false and illegal based on the code sections referenced.


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## HomeSealed (Jan 3, 2008)

AGWhitehouse said:


> This a potentially false statement as it is in potential direct conflict with section R316.5.3 Attics from the 2009 International Residential Code. It reads as follows:
> 
> *R316.5.3 Attics.* The thermal barrier specified in Secion R316.4 is not required where all of the following apply:
> 
> ...


Thank you for saying "potentially":laughing:
My comments and recommendations on this are based on my professional training and experience in this specific area, as well as my daily interaction with local building inspectors and officials of federally funded energy efficiency programs. Of course what I should have added is: Be sure to check with your local building department for their interpretation and enforcement of code. :thumbsup: Around here, it is widely accepted among the community of home performance professionals and building inspectors that XPS does not need to be covered up if outside of the building envelope. In a specific recent example, we had a client with a turn of the century home that had a finished room in a walk-up attic, where you walked through unconditioned attic space to get to the room. The energy auditor spec'd XPS board over the plaster facing the unfinished attic, and it was approved by the inspector. I would be interested to know if things are done differently in your area. Perhaps you could share an example? 
In addition, if you are going to quote my comments in the future please do me the courtesy of quoting my entire comment so that it is not taken out of context or lacking the explanation/reasoning behind it.


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## Gary in WA (Mar 11, 2009)

I agree,check locally. Chapters 4; http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1826.pdf

http://commercial.owenscorning.com/assets/0/144/172/174/5deb06d2-43b4-44b2-b4ec-20579af27e5d.pdf

http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2670.pdf

Gary


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## ryanmcl (Jan 7, 2013)

So if i want to finish my basement slowly over the course of the next two years do i frame and use fiberglass batts? I don't see how i can possibly use XPS if it needs to be covered within 30 days.


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## VonTed (Feb 6, 2013)

Save your pennies and do it all at once. It takes relatively little time to install the XPS on the walls.... once the XPS and insulated walls are up take your sweet time "finishing" the basement.


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## AGWhitehouse (Jul 1, 2011)

HomeSealed said:


> Thank you for saying "potentially":laughing:
> My comments and recommendations on this are based on my professional training and experience in this specific area, as well as my daily interaction with local building inspectors and officials of federally funded energy efficiency programs. Of course what I should have added is: Be sure to check with your local building department for their interpretation and enforcement of code. :thumbsup: Around here, it is widely accepted among the community of home performance professionals and building inspectors that XPS does not need to be covered up if outside of the building envelope. In a specific recent example, we had a client with a turn of the century home that had a finished room in a walk-up attic, where you walked through unconditioned attic space to get to the room. The energy auditor spec'd XPS board over the plaster facing the unfinished attic, and it was approved by the inspector. *I would be interested to know if things are done differently in your area.* Perhaps you could share an example?
> In addition, if you are going to quote my comments in the future please do me the courtesy of quoting my entire comment so that it is not taken out of context or lacking the explanation/reasoning behind it.


Sure are...rule of thumb here is if you can physically get to an area where you can see the foam after installation, then it needs to be covered. The only exception being right along rim joists and top plates because that is a direct exception to the code here. My 13 years in CT has always been 100% to the letter of the code. If the code says it, it's done, no question. Any exceptions need fully documented approvals. The "evaluation reports" that GBR posts alot as exceptions only are applicable here if the AHJ signs of on a code variance with them as submitted evidence of general compliance with the code intent. Was hired on a job a couple years back after they were instructed to demo out all of the sheetrock because the AHJ found a few instances of improper fire rating measures. lawsuits abounded, but every single fire joint was inspected and individually approved. CT is, generally (not always), very much by the book...sometimes I feel like I'm more lawyer than architect as I've had hour long debates with colleagues over the verbiage of a code line.


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## HomeSealed (Jan 3, 2008)

Fair enough AG. Like anything else there are some areas in code that require "interpretation", however ultimately the advice that we all gave in regard to checking with the local building department is best.


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## Windows on Wash (Aug 30, 2011)

Totally depends in this area as well.

I have gotten 3 different answers from inspectors on the same job go figure.

If you want to make sure you are covered...cover it.

Potentially....I love it. AG for Political Office.


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## Gary in WA (Mar 11, 2009)

Lol, WoW, that is funny, and probably from the same employer... Here is one for you;

1" STYROFOAM rigid sheeting on attic knee wall covered *with Tyvek *on attic side not requiring a thermal/ignition barrier; *4.2.1.3*;http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2142.pdf
From, for further research; http://www.iccsafe.org/Pages/SearchResults.aspx?cat=StoreSearch&q=thermal/ignition%20barriers%20for%20XPS

If no access door/hatch to the attic (size limited, 30sq.ft., 30" high, per IRC, that requires access), or flooring, and other requirements; no ignition/thermal barrier is required;http://www.icc-es.org/News/Articles/AY126ThermalBarriersSPF2011-51811.pdf

More info on the* ICC-ESR papers* I sited earlier (and forgot this link) and* how *to get a report, when talking to your inspector; http://www.icc-es.org/Help/about.shtml

Gary


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## AGWhitehouse (Jul 1, 2011)

Call me a scaredy-cat, but with the way this stuff burns, I have yet to really question the IBC's requirements for an ignition and thermal barrier. All those evaluation reports are manufacturer's trying to skirt the extra expenses of ignition barriers and get their product put EVERYWHERE. It's my opinion that foam products have places they're great and places they stink...balancing life safety to put something somewhere it doesn't want to be isn't good building practice, it's usually done for good business and we all know good business doesn't always mean good practice...


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## Windows on Wash (Aug 30, 2011)

+1

When in doubt...cover it.

When I do my home...I will be covering it as well.


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## RTC_wa (Mar 12, 2013)

well yah its going to be toxic if you burn it. But how many times are you going to stay in a home that is burning down around your head? put it in cover it up call it good don't lose sleep over it.


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