Re: Straw Bale Info
From: Buzz Burrell (72253.2101compuserve.com)
Date: Fri, 16 Jun 95 10:37 CDT
Although the information on the insulation values of straw bales was right in
front of me, I didn't reply to Harry's question at the time because it was so
angry and confrontational;  I stayed away from it.  However, now that it has
come up again, here are the tests I've seen ...

Harry said:
>* Tested R Value of Straw Bales:
>- Can you give me the name of the accredited laboratory (for testing
>insulation) that tested the "R" value of a fresh straw bale and an aged straw
bale ?

David replied:
>As far as testing the R-value of an aged straw bale, I am quite sure that
>that has not been done.  I wonder what the point of this question is, though?

Stacked flat (normal), 2 laboratories tested straw bales and came up with an
average value of R-2.5/inch.  Since most walls are 24 inches, that would achieve
the huge figure of R-60 for the wall (not figuring in the stucco and plaster).
Since fiberglass is R-19 at the standard 6 inch thickness (or R-21 for the high
performance version), plus the sheathing, siding, and wallboard, that means a
straw bale wall would have, in a worst case, twice the insulation of fiberglass
in it's absolute best case;  three times the value is not unsubstantiated.  

"The bottom line though, is that bales insulate extremely well". (see reference
below)  

Those values are not for "aged" bales.  But once it is plastered and stuccoed, a
straw bale would be expected to compress, shrink, or otherwise lose insulation
value at the same or less rate than fiberglass insulation loses value.
Fiberglass is well-known for not performing according to its rated value (gaps
near studs, gaps around plumbing and electrical, thermal bridging at studs,
installer incompetance, settling, etc).  Therefor, I'm not sure why there would
be any difference between aged and new bales (again, once they were installed).

I wish to compliment David on his thoroughly researched and well-reasoned
information, and the efforts he is putting into developing this wonderfully
promising technique.  He is mentioned in the current issue of Environmental
Building News, which is where I got the information and the quote above.  The
May/June issue has a very scientific and exhaustive analysis of Straw Bale
construction, which would be highly recommended for anyone looking into this
method.

For example, and also regarding the ecological aspects of using straw, they
calculated that if all the straw produced in the US was used in straw bale
houses, that would be build 2.7 million houses.  Each year.  Since straw is a by
product and not a crop as David said, that is an extrodinarily ecological
solution.

EBN again:  "As with many new ideas, the use of straw will meet lots of
resistance along the way, and it may find very slow acceptance, but we feel that
its environmental and economic benefits will ultimately result in its widespread
use."  (Just like cohousing).

Environmental Building News
RR1, Box 161
Brattleboro, VT
05301


Buzz Burrell
Boulder

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