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Spray foam and fire

I have read, without verification, that spray foam will become an accelerant when heated to a high degree. There was a new house that was built by a reputable builder, they used spray foam and the house burned very quickly. There was no evidence of arson.

I have a client who wishes spray foam and I prefer sprayed cellulose. Does any one have evidence other than anecdotal?


Asked by john winkler
Posted Nov 30, 2012 10:34 PM ET
Edited Dec 1, 2012 6:51 AM ET


10 Answers

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There are two issues here. The first question is whether the heat given off by the exothermic reaction that occurs when spray foam is installed can, under certain circumstances, cause ignition that leads to a fire. GBA has written several articles on that topic, including these:

An NZE Project, a Tragic Fire, and a Will to Rebuild

Three Massachusetts Home Fires Linked to Spray-Foam Installation

The second question concerns whether a fire of unrelated origin -- for example, an electrical fire or a fire started by a cigarette -- burns hotter or faster in a house insulated with spray foam than it would in a house insulated with cellulose. I believe that the answer to this second question is yes, but GBA has no articles on the topic.

Answered by Martin Holladay
Posted Dec 1, 2012 6:44 AM ET

Answered by John Klingel
Posted Dec 1, 2012 4:32 PM ET

Answered by Hein Bloed
Posted Dec 18, 2012 6:46 PM ET


Pure fear mongering.

Next asteroid mass deaths looming just around tbw corner.

Answered by aj builder, Upstate NY Zone 6a
Posted Dec 18, 2012 10:36 PM ET


The link provided by Hein Bloed leads to a forum discussion, and that forum discussion includes a link to a video of a fire at an 18-story building in Roubaix, France:

Wow! Talk about scary. One person died in the fire. I couldn't find much information -- in either English or French -- on the fire, except a reference on another website to the fact that the fuel for the fire was some type of "synthetic siding." Although the fuel was probably some type of rigid foam, I'm not sure what the burning material was.

Answered by Martin Holladay
Posted Dec 19, 2012 8:14 AM ET


That was mineral wool in Roubaix, a wind proof membrane covering the mineral wool was synthetic - as far as I know. As well as with the Moskau fire.

The fire in Dubai was PU foam.

The Frankfurt fire was graphit enhanced EPS.

If you need translation help ( fluent German ,Dutch and very limited French) for technical details on these fire issues let me know.

Answered by Hein Bloed
Posted Dec 19, 2012 9:43 AM ET


Both cellulose and polyurethane foam will light off and become a self-sustaining fire if you get it hot enough and provide it sufficient air. Key to slowing flame spread inside of studwall cavities is air-retardency and filling the cavity completely, since even at temps well above the kindling point it won't burn or spread without an air supply.

The practice of using closed cell foam at less than full cavity depth and leaving an air space between the foam and gypsum is code-legal, but not good practice, even if framed with fire-stops. But open cell foam trimmed flush to the studs is hard to light off. A handful of years ago in central MA a fire in an antique mill building burned most of it down, but the section insulated only with open cell polyurethane incurred only smoke damage.

There have been numerous instances of closed cell foam self-igniting as in the GBA article, usually when applied in lifts thicker than recommended by the manufacturers, but that's the extreme exception, not the rule. I don't know of any cases where this has happened with open cell foam, but most manufacturers specify a 5" or 6" per pass limit even with open cell (a limit often ignored by installers.)

In a single family house by the time the foam is at a temp high enough that it's an accelerant and exposed to sufficient air that it really takes off, it's unlikely that the house (or anybody still in it) would have been saved.

Rainscreened siding cavities on foam sheathed houses is still a potential fire-spread hazard that some local inspectors take issue with, but there isn't much field evidence that it is a menace to be avoided.

Answered by Dana Dorsett
Posted Dec 19, 2012 12:57 PM ET


Since the OP is not looking for anecdotal stories but for clear evidence:


And " ... that spray foam will become an accelerant when heated to a high degree " has to be made clear.
The chief of the fire brigades of Frankfurt/Germany says so, the chief of the fire brigades of Berlin/Germany says so.

All experienced firefighters call for a ban of these substances in the construction sector.
It is an an accelerant without doubt.

The combustion test done to ISO standards should be video taped if the test lab is acredited by the
Ask your prefered manufacturer for this video tape. If they deny that question you know you have asked the right question.

Nothing wrong with reality.

Answered by Hein Bloed
Posted Dec 19, 2012 7:53 PM ET
Edited Dec 19, 2012 7:54 PM ET.



In particular


which had been altered recently (new ISO number/title?), the test being done now in a vertical shaft and not only in a corner as previously demanded by the ISO.

Since most foam filled cavities are penetrated (cables, pipes, ductings but also doors and windows) the wall coverage does not guarantee a fire safety on its own.

The heat exposed foam will melt upwards - that's where hot air goes naturally- and will create a duct, a chimney within the wall. Unseen,undetected. See here a Swiss fire brigade in action, enlarge the picture:


This fire was detected because it was broad daylight, the smoke being seen from outside. At nightime a catastrophe would have happened before detection.

Again: ask your prefered manufacturer/installer for the ISO test protocol, the video etc..

Anecdotal stories on car safety called for Ralph Nader to campaign for safety belts. Nowadays the safety of cars is tested.
Most people spend more time in buildings than in their cars. And in buildings most dy.

The test procedures are there. Ask for the documentation.

Answered by Hein Bloed
Posted Dec 20, 2012 8:06 AM ET
Edited Dec 20, 2012 8:12 AM ET.


Here's the photo of the fire in Switzerland that Hein Bloed is talking about.

Fire in Switzerland 2.jpg
Answered by Martin Holladay
Posted Dec 20, 2012 8:55 AM ET

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