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Re: GSBN:Question re R-values
Bob was involved in the research that led to the Energy Commission report,
as were Greg and Turko (those Straw Dawgs), David Eisenberg, and myself.
The numbers were all over the place. However, the best test gave a value
that equates to about R-1.5/inch. for the 'standard' bales in central
California (~22.5" wide), that results in an R-33. The Energy Commission
took the conservative approach of assigning straw bales walls an R-30,
until someone comes along who has the time and energy to devote to more
I generally tell people who ask that the tested value is around R-30, but
that in California, the walls perform more like R-45 due to the thermal
lag. I put the "California" qualifier in there because in a location where
the temperature drops below freezing and stays there for a couple weeks,
the tested value is likely to be the more accurate one. The thermal lag
only comes into play where the day time temperatures are significantly
higher than the night time temps.
> [Original Message]
> From: Bob Bolles Bob@...
> To: GSBN GSBN@...
> Date: 12/29/2004 10:37:13 AM
> Subject: Re: GSBN:Question re R-values
> 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,
> > 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
> > are reviewing a project in the Northwest USA.
> > I'm wondering what answer you would give to this question?
> > Joyce
> > --
> > Joyce Coppinger
> > Managing Editor/The Last Straw, the international quarterly journal of
> > strawbale and natural building
> > The Green Prairie Foundation for Sustainability/GPFS (publisher)
> > PO Box 22706, Lincoln NE 68542-2706 USA
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> > of
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> GSBN is an invitation-only forum of key individuals and representatives
of regional straw construction organizations. The costs of operating this
list are underwritten by The Last Straw Journal in exchange for use of the
GSBN as an advisory board and technical editing arm.
> For instructions on joining, leaving, or otherwise using the GSBN list,
send email to GSBN@...HELP in the SUBJECT line.