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GSBN:Re: Question re R-values

I think it is risky to pretend that a complex issue is simple, to satisfy a
momentary need.  In talking with clients, enthusiasts, code officials and
the curious, I am constantly bemused by the mis-application of information,
and the incorrect analysis and extension of data.  At a minimum, I feel it
is essential to quote a source for any simplification, as Bob did below.

Most people that I talk to are mentally comparing strawbale to the myths of
the US insulation grail, R-19 fiberglass batts.  If I say that strawbale
has an R-value of thirty, many people conclude that it is just a little
better than fiberglass.  I prefer to say that strawbale as a building
component has an R-value of 50, according to tests at Sandia National
Laboratories tests.  I compare this to the R-19 fiberglass that they are
familiar with.  Next I say that a well-built SB wall will have an R-value
of around 30, according to Oak Ridge National Laboratory (ORNL) tests.  I
compare this with the ORNL ratings of R-7 to R-11 for a wall insulated with
nominal R-19 fiberglass.

I find that most people have never considered the possibility that R-19
fiberglass doesn't guarantee an R-19 wall.  However, they can understand
and accept the concept that a whole wall will have a lower average
insulation value than its most insulating component.  I also mention that a
poorly built wall, whether insulated with SB, fiberglass, or anything else,
can have a much lower insulation value.

This is the simplest way to answer the R-value question that I have found,
while still being effective in conveying some of the essential information,
and providing a fairly accurate basis for comparison.


Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek@...

--On Wednesday, December 29, 2004 10:10 AM -0800 Bob Bolles
Bob@... wrote:

California Energy Commission has set Straw Bales at R-30, and that is the
value we use.

Bob Bolles
Sustainable Building Systems
San Diego, CA - USA

----- Original Message -----
From: "Joyce Coppinger" jc10508@...
To: "GSBN" GSBN@...
Sent: Wednesday, December 29, 2004 10:04 AM
Subject: GSBN:Question re R-values

When answering the question about R-values of bale walls and buildings, I
usually use a range rather than a specific number. A request has come in
asking for a specific R-value to satisfy the building codes officials who
are reviewing a project in the Northwest USA.

I'm wondering what answer you would give to this question?


Joyce Coppinger
Managing Editor/The Last Straw, the international quarterly journal of
strawbale and natural building