SB: FWD: Re: Fireplace in Bale Wall

[Robert W Tom <archilogic@juno.com>]

--------- Forwarded message ----------
From: Mark Piepkorn <duckchow@greenbuilder.com>

        OK, well, as long as I'm already talking, I'll just go ahead and
dig
myself a bigger hole.

*

>Does anyone have experience building a bale wall 
>with a fireplace in it.

        I didn't build it, but I have experience with a fire in a
plastered bale
wall that was started by a fireplace that wasn't built in the wall, but
against it. Info on that follows further below.


>The design the owner wants is a fireplace with a 
>window on each side in the gable end wall...
>
>Concerns relate to supporting weight of the bales 
>in the gable end wall triangle, placing a 
>fireplace in a bale wall (fire is the basic 
>concern here), and minimal wall space between 
>windows and the fireplace as well as from the 
>windows to the side walls.

        Sounds as if some sort of bearing structure is going to be
required, if
not simply desired, since the amount of space from the corners to the
windows, and the windows to the fireplace (not knowing the particulars of
the design and what consequences spring from it), are "minimal." So
already
the bales are nonstructural in addition to being not all that likely to
significantly temper the thermal qualities of the wall as described.
Without knowing bunches more details, it sounds reasonable to me (and
like
less work, too) to use something other than bales to insulate that wall.
Or
the lower half of that wall, anyway.


>We've talked about dipping the bales around the 
>fireplace and chimney in a slip and mortaring 
>them together and then using uncoated bales for
>the remainder of the wall.

        I get why thoughts turned to dipping, but I'm not sure what the
mortaring
is for; is that for structure, to help hold up the gable bales?

        I guess I'm seeing things like structural window bucks with a
sort of
ladder plate on 'em for gable bales (which might 'cantilever' into the
room
over the less-thick wall below it to nice effect; perhaps an opportunity
to
introduce a bit of Sun Ray madness in the form of tree trunks in the
house
- with limbs and all - on either side of the windows, like columns,
disappearing into that cantilevered section... sort of like the hatrack
in
Steve MacDonald's house. I think there's a photo of that in The Straw
Bale
House and also in The Beauty Of Straw Bale Homes, and for sure in that
Straw Bale Homes Tour video).

        So, about that fire I mentioned at the top of this email... this
next
little bitty piece was in The Last Straw #31 (Fall 2000). I was there
when
this happened.

-----

Trial By Fire
Catherine Wanek

Y2K nearly proved fatal to our straw-bale/cob hybrid building we call
Casa
Chica. A group of New Year's Eve party-goers stayed up late there on
January 1st, drumming into the night. Since the door and windows are
unfinished, they created a blazing fire in the cob fireplace to keep
warm.
The next morning someone noticed flames coming from one corner just in
time, and the fire was quenched before it reached the roof.

We have had many fires in that fireplace before, so what happened? The
best
guess is that over time the cob was "fired" and became ceramic. The heat
vaporized the straw in the cob, leaving spaces for hot gases to travel
through. And, the cob fireplace adjoined a straw-bale wall, without an
air
gap. This combination allowed sufficient heat into the bale wall to start
it smoldering beneath the plaster. Hours later it reached a wooden post,
which did catch fire, and luckily that's where the damage stopped.

The lesson? There's a reason that building codes call for an air gap
between adobe and combustible materials. We will certainly heed this in
repairing the damage. It's easy to have disdain for the "overkill' codes
often require, but remember that codes exist for our health and safety,
and
as they say, know why the rules exist before you break them. 

-----

        The fireplace in question, as mentioned, wasn't cement block or
fired
clay. It was cob. It was built up against an earth-plastered bale wall;
there was a minimum of a about four to six inches of cob between the fire
chamber and the bales.

        How the bales got to smoldering is a subject for speculation.
There's a
couple good theories about it. Thing is, at least in my opinion, there
oughtta have been a vented air space between the firebox enclosure and
the
wall system itself. Norbert Senf (and lots of other people) can speak to
what's really needed better'n me; this is just my own opinion based on
whatever I'm basing my opinions on. (By golly, Norbert has indeed weighed
in while I've been fighting the list software, which is totally ignoring
me
- I can't subscribe! If I can't subscribe, I can't post. Sigh. I knew
there
was a good reason I became a lurker.)

        Whether or not anybody speaks to that here, it's something to
find out.
The article said, "know why the rules exist before you break them..."
what
it didn't say is that you have to find out what the rules *are* before
you
can find out why they exist so you can safely break 'em.

        Sigi Koko, who I've been pleased to see posting here from time to
time,
had an east coast project where they were going to encase a
brick-and-mortar fireplace in cob. The code official was having some
troubles with the idea; I don't know how that turned out. Sigi?

        Finally there's that ASTM E 84 (flame spread and smoke
development) test
that was performed a while back, which DE posted about here a while ago.
(The results have been posted to the DCAT website somewhere, them good
folks having acquired the test results from Katrina Hayes.) While the
results were excellent, let me assure anyone who hasn't been around a
smoldering bale wall that they can smolder GOOD. As tricky Rob Tom has
pointed out on this list in the past, most people who die in house fires
don't die from the fire; they die from the smoke.

        The following article was also in The Last Straw #31 (Fall 2000).

-----

Straw Bales and Flame Spread 
Howard Switzer - Nashville, Tennessee 

Months ago one of my clients, Katrina Hayes, was having difficulty
getting
a permit for a straw-bale garden shed she wanted to build. The Sumner
County building official was requiring ASTM E 84 (Flame Spread) test
results. The considerable evidence of strawbale's fire resistance
indicated
in the successful ASTM E 119 test was not good enough for him. I
contacted
David Eisenberg to find out who could perform such a test and he gave us
the name of the two labs in the country that could. At long last Omega
Point Labs in Texas agreed to do the testing for $850. Katrina contacted
Cat Brown at the Straw Bale Association of Texas, who contacted "Straw
Locator" Karen Nordby who delivered eight bales (donated by Jo and Clint
Wilhelm) to the lab and the testing was done. 

The ASTM E 84 Standard Test Method for Surface Burning Characteristics of
Building Materials tests for flame spread and smoke development, the
latter
extrapolated from measurements of smoke density. The Standard Building
Code, as well as the UBC, requires a maximum flame spread index of 75 and
a
maximum smoke developed index of 450. Straw bales passed the test with...
drum roll please... a flame spread index of 10 and a smoke developed
index
of 350! 

Flame spread ratings are listed in three classifications. Class 3 is the
worst rating, indicating a combustible material. Class B material is in
the
intermediate range and has various uses in commercial construction.
However, class I (A) material which is below a FSR of 25 is considered a
fire-retardant material. Stress this point to building-code officials.
The
E 84 and E 119 are the only two tests relating to fire that are required
by
code that I'm aware of, so getting permits should be greatly enhanced by
these results. Three cheers for Katrina and straw bales! 

Katrina would be happy to share the official results for a $10.00
donation
to offset the $850 that she paid for the testing. Her address is (please
email thelaststraw@strawhomes.com if you want this info). "Ecoville
architect" Howard Switzer helps owner-builders and others build
passive-solar buildings using plastered straw-bale construction, and
presents workshops with his partner Katey Culver throughout the South to
educate folks on what truly constitutes sustainable building. Email him
at
ecoarchitech@earthlink.net
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