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Re: GSBN:fire test -- your opinions?

Hi all,

Interesting points re: edge vs flat, cement vs cement-lime vs lime vs
earthen plasters.

I think it's clear that order to really get the full data, more than
two tests will need to be done. Typically in a scientific procedure
you'd change just one variable at a time, for instance bales on edge
vs bales flat, with all other variables (plaster, etc) remaining the
same. Then you'd vary another constraint, such as the plaster types,
so that if you'd already done edge vs flat with one type of render
you'd be able to predict how the performance would vary (or not)
using different plasters as a result of bale orientation.  Otherwise
you have trouble saying exactly what caused any difference you may
have observed.

I personally don't think that we'll see a huge difference between
edge vs flat, though I can certainly see the reasoning behind doing
such tests to be sure.  I don't think molten strings are going to
make much difference, especially in a test wall which is built within
a four sided frame - it's not likely that the straw is going to go
anywhere. The question is more a matter of how heat is transferred
through the bale - do the hollow straws allow it to move faster
through flat bales?  Do vertical straws cause heat to move to the top
more quickly, causing failure there?

Regarding plasters, curiosity got the best of me and I pulled some
numbers from the SB Registry to see just what people are using on
their walls.  For exterior walls, they can choose from:

cement plaster
earth or clay plaster
lime plaster
wood siding over plastered bales
wood siding over unplastered bales
other - Describe if other

or any combination of the above.  Of those who reported their
exterior finish, the resulting numbers are:


Cement only: 235

Earth only: 72

Earth/lime: 34

Lime only: 51

with a scattering of other strange combinations (perhaps different
treatments for different walls).  For interior walls, they can choose

cement plaster
earth or clay plaster
lime plaster
gypsum plaster
other - Describe if other

or any combination.  The resulting numbers are:


Cement only: 116

Cement plus other: 39 (includes cement & gypsum, cement & sheetrock,
cement & wood, etc)

Earth only: 94

Earth & Gypsum: 13

Earth & lime: 13

earth & other: 15

and again, a few who did other, more bizarre combinations.

So though these numbers are by no means definitive, it looks to me
that cement beats earth for exteriors in general by about 2 to 1, but
they're pretty close to an even match for interiors.

Which then begs the question:  Are we testing for fire resistance of
interior walls or exterior, or both?

On the flat vs edge orientation, I see 316 flat vs 84 on edge.

I don't know if those numbers will help anyone make a decision, but I
figured I'd throw them out there.  There's more reported use of earth
plaster than I expected there to be.

Bill Christensen
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