SB: Re: Topping off the walls/insulative value &creep

["Steve Lewis" <seaweedsteve@newmexico.com>]

Hi.  Lootvik.    Actually, I did see your post on R-values after I responded
to Rob Tom.
Still, I stand behind what I said.  Many times "facts" are only as relevant
as the assumptions they are based on.

1) As I said in my follow-up post ,  perhaps my term was inaccurate or not
well defined.  I should have said perhaps, "slip-straw".  Also, the
application technique matters a lot.  German light clay is rammed, and
seriously from what I can tell.  A whole different animal than "stuffed or
packed".   One indication of the level of density you are getting is what
the ratio of unpacked to packed  straw/clay is in your application.  Light
clay has a high ratio, that is, the volume of mixed material compared to the
volume of wall filled.   Straw stuffing, whether coated in slip or not, has
a low compression  ratio.  A bucket full of stuffing will fill a hole 1/2
it's size more or less.

SO. When we refer to numbers from a book in Germany about an application for
what are probably  rammed light-clay wall panels, we are not really getting
info on crack-stuffing.  To be most accurate, we would want to check the
density of straw-clay stuffing and find where it lands on the scale between
bales, light clay and cob.  I sense that it is closer to bales than light
clay.

2)  Assuming I do RAM it in with a tamper, say,  (I don't)  and get a
light-clay density with  R- 1.4 per inch, what do you have at 24 inches?
R-34.  Would you call that "minimal" ?

Few houses are 100% insulated evenly.  We shoot for that.  Framing,  posts
and beams compromise insulation, as do window and door bucks (forget windows
and doors!),  stuffing, many things act to reduce the net R-value to well
below the "nominal" R-value.  A code specified R-19 house is well below that
when the fenestration and framing members are acounted for.

A six-inch band around the house that is R-34 or likely better seems ok to
me.


Cheers,
Steve



----- Original Message -----
From: "*Lootvik*" <lootvik@usermail.com>
To: "Steve Lewis" <seaweedsteve@newmexico.com>
Sent: Thursday, November 29, 2001 1:38 PM
Subject: Topping off the walls/insulative value &creep


> R 1.442 down to 0.103 per inch.  Strawbale is between 2.38 [bale laying
> down] and 3.15 [bale standing up] per inch.  Did you see my "Straw clay R
> value" post?
>
> The closest you might get is HALF the value as sb.  Like RT said, that
clay
> is filling up the air spaces with a very good heat Conductor--clay.
>
>
>
> >Rob Tom wrote:
> >
> > > The insulative value of straw/clay mixtures can range from negligible
> > > to minimal, depending upon the density of the mix.
> >
> >Rob, you know, I thought to specify the density of the straw-clay mix in
my
> >quip, but didn't.  I use straw dipped in slip then stuffed in.  Might
just
> >use flakes at six inches.   For areas that need more forming (like
edges), I
> >add enough clay to give it some body.  But for mass filling, keep the
> >material light and mostly straw.
> >
> >I believe that a 24" inche thickness of straw-clay filler is far more
than
> >"minimal"  insulation with a low density mix.   Perhaps you are
refferring
> >more to cob levels of density.   Certainly adding a thin clay coating to
> >straw does not change it's insulative properties THAT much.  Just gives
it a
> >fire-proofing and helps it stuff better.
> >
> >Now long term creep is a concern to me.  Which materials will expand to
> >counter that effect?  Maybe compressed flakes are better, they can spring
> >out a bit.    This is one of those areas in which Nebraska-style seems
more
> >elegant.   The building is more of an integrel unit and anyway,
> >pre-compression is the norm.
> >
> >Steve Lewis
>
>


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