Re: Straw Bale Info | <– Date –> <– Thread –> |
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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