[GSBN] Fire Case Studies

[Frank Tettemer]

I can't and won't equivocate around your memory, Rob; I'm sure that it's 
just fine!
I can vouch for all the contents of your description of the changes in 
the flash point of the cellulose.

John Gulland, (the author of Wood Heat dot org), has shared this 
similar/same information with mea long while ago.
We had talked about it in the context of standard wood frame 
construction.  Many builders, who lack combustion engineering, often get 
it wrong. That's most of us carpenters.

First the idea that plasters all act as a fireproofing technique, 
instead of offering fire resistance
Second the idea that standard gyprock is in some way inflammable, 
instead of fitting into the class of flammables. We've known this for a 
long time now.

I have participated in a kitchen demolition where the old cookstove had 
stood in that same place for a long time.
Likewise,  within the wall frame behind the stove, the spruce two by 
fours had stood there even longer.
As was the rule of the day, the stud cavities were irregularly filled 
with fiberglass batts, with brown paper backing, lightly coated with 
asphalt, to bear witness for the need of a vapour barrieron this wall.

The fire was contained to the back kitchen, and then the fire department 
managed to put it out. The Forensic investigator from the insurance 
company was puzzled, saying that the stove had been too close for 
acceptable fire clearance for decades.
It had survived all that time, and just now created a fire. Why did it 
take so long?

This is my third reason to back you up. It's about the combination of 
repeated periods of high heat, baking the wood resinsout of the 2x4's, 
over a long time period that is responsible for lowering the flash 
point. In this case, wood frame cellulose, but in any case of cellulose, 
such as dense packed cellulose walls, or, well plastered straw walls, 
there is the need for caution.
For builder's, the need for caution, if the chimney or stove 
specifications are not honoured. Heat shield behind the stove can help.
For designers, the need to be diligent with accurate dimensions, in 
creating the chimney locations to provide adequate fire clearances.
We know this stuff now, and we can all feel the resulting karhma, and 
the huge, Huge decrease in house fires. We can all feel good about 
continually learning and applying knowledge.

Frank Tettemer


On 2018-06-14 1:56 PM, RWT wrote:
>
> on Wed, 13 Jun 2018 bob at bobtheis.net <mailto:bob at bobtheis.net> wrote
>  Re: [GSBN] Fire case studies
> Message-ID: <CEF3C68A-587A-47F1-8F0F-5E3D64323F1F at bobtheis.net 
> <mailto:CEF3C68A-587A-47F1-8F0F-5E3D64323F1F at bobtheis.net>>
> Content-Type: text/plain; charset="utf-8"
>
>
> > Makes me wonder if these massive-looking  bale walls register 
> subliminally as masonry,
> > so people drop their inherent caution about keeping combustibles 
> away from fire.
>
> ================================
>
>
> Bob and PyroBaleHeads;
>
> I have vague memories from years ago of masonry stove builder 
> extraordinaire/engineer Norbert Senf  'splainin' to us on one of the 
> SB lists the phenomenon of thermal decomposition of cellulosic 
> materials like wood framing (and by corollary straw bales) in inert 
> environments like wall and ceiling cavities when subjected to 
> long-term exposure  to elevated temperatures as would happen when 
> proper clearances aren't provided between the cellulosic material and 
> wood burning appliances, exhaust flues and such-like.  If I remember 
> correctly, chemical changes to the cellulosic material takes place 
> that results in a lowered ignition point of the material so that an 
> assembly that otherwise might not burst into flame, will unexpectedly 
> ignite .    I've copied Norbert on this message and hopefully he may 
> find a moment to point out how badly my memory had faltered.
>
>
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