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RE: GSBN:CalifoRnian values (was re: from the Crest list)
- To: GSBN GSBN@...
- Subject: RE: GSBN:CalifoRnian values (was re: from the Crest list)
- From: Derek Roff derek@...
- Date: Sun, 11 May 2003 17:44:28 -0600
- Reply-to: "GSBN" GSBN@...
- Sender: "GSBN" GSBN@...
The difference between R-30 and
R-45 means the difference between 0.033 Btu/hr/SF/F and 0.022
Btu/hr/SF/F. Repeat after me, "It just doesn't matter! It just
doesn't matter." I suggest we move on to other, more meaningful
In terms of a functioning house, I agree with Nehemiah that the exact
R-value for SB doesn't matter. I also like the statement that I
first heard from Danny Buck of Living Structures: The R-value of a
strawbale wall is "enough."
When it comes to educating the public about strawbale building, I
feel a need to say more. What I say these days is something like, "A
straw bale has a R-value of 45 or 50. A well-built wall can have an
R-value of 30 for the entire wall, according to tests done at Oak
Ridge National Laboratories. Fiberglass batts for 2 x 6 framing are
rated at R-19 for the material, so that's less than half of the value
for a straw bale. Oak Ridge tested frame walls insulated with
fiberglass batts, and measured R-values from a little over R-7 to
R-12. As with the raw materials, a fiberglass-insulated frame wall
will yield less than half the insulative value of a strawbale wall."
I haven't figured out a way to say it more concisely, and still
convey the needed information. Plenty of people have come up to me
and said, "I hear that strawbales are only R-30. Since fiberglass is
R-19, why should I bother with bales?" I think it takes a bit of
explanation to clarify the fallacies in that kind of statement.
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