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  • From: YankeePerm@aol.com
  • To: permaculture@listserv.oit.unc.edu
  • Subject: Re: passive solar greenhouse/strawbale
  • Date: Tue, 11 Nov 1997 09:06:43 -0500 (EST)


In a message dated 11/11/97 7:07:01 AM, you wrote:

>We live in the northwoods of northern Minnesota, near the headwaters of the
>Mississippi River. We built a strawbale studio 4 summers ago for Cheryl's
>holistic health practice. We have only glowing reports to give on its
>performance and esthetic appeal.
>
>You mentioned "a number of reasons" strawbale can be questionable
>here...please shed more light on this...
>
>Bruce

1) It is not a place where a lot of straw is produced. Wood is produced in
woods. Therefore wood is in abundance and more appropriate, all things being
equal. Given the proven performance and durability of cordwood (stackwall)
construction, which leaves the biggest and best trees in the forest and need
only thin what would be crowded out anyway, this is another suitable
construction method.

2) Heated cold climate structures invite rodents. Straw bales invite
rodents. The combination is a compelling invitation to rodents. Strawbale
construction sometimes uses bales as bearing walls. It would be difficult to
replace infested sections. This would be less difficult where post and beam
construction and strawbale infilling are used, but still one does not look
forward to routinely replacing walls.

3) The humidity issue is very serious, I think, both as a potential
compromise of the insulating value of the wall and as a promoter of decay
organisms, particularly fungi. "Grow shiitake at home!" :-) North woods
means humidity, or it would be north prairie. As previously posted, vapor
barriers on easy to seal surfaces fail to an extent that they are being
discontinued in some recommendations where experts feel that the vapor
barrier may do more harm than good.

4) I cannot imagine a straw bale bearing wall that will not be compressed
beyond acceptable limits by a heavy snow load of say two feet turned to solid
ice by spring ice storms. Anyone who has live in a genuine winter climate
long enough has experienced this. Of course there are perfectly sound ways
to build with straw bale, as merely a weather barrier and not as load
bearing, that avoids this problem.

>From a performance viewpoint, the humidity factor is the one that most
concerns me in humid climates. This would not show up in initial performance
but in deterioration of performance over time. I'd be delighted to learn of
proven techniques that avoid this. Of course in the climate where I now
live, straw bale would be reduce to termite frass in about two years, I
reckon, without horrifying doses of toxins.

There is a good argument to be made for houses that function at the forest
edge for a certain period of time and then melt back into the soil. You
could pull out your windows and throw a beech nut in the mess and move out
ahead of the successional line of forest again. While a lovely way to live,
and reminenscent of very joyous tribal lifestyles, it is a bit tough in a
world with 6 billion people needing some space to lie down once a day. Alas.
I first heard this very permaculturally appropriate idea from Jack Henstridge
, one of North Americas two cordwood experts, in referring to cordwood using
clay instead of concrete as binding material. He figured 20-30 years for
such cycles--I'd guess 5 to 10 years for strawbale deliberately managed in
this way. I don't know how strawbale will hold up in a humid climate where
we do everything we know to preserve it except to apply toxics. Frankly, I
doubt anyone does.

Also in today's email was a private note from someone on this list who has
access to a published research report on strawbale performance. Since I have
not read it, I should not repeat hearsay. However I am hopeful that this
prod will get him to summarize the report for this mailing list. Please?

To repeat, since it is easy to lose sight of context in these exchanges, I am
convinced that strawbales have many useful applications in shelter. I have
seen brilliant hot beds and cold frames put together with them in Kansas and,
copying that idea, took it a step further and used them as a growing
substrate, as described in Kourik's edible landscaping book, after the need
for hot beds was past. Later they were pretty well on the way to compost and
I used them as mulch. That was a wonderful system. In Georgia, I couldn't
get straw and tried the same with hay--a total disaster. The hay has too
much nutrient and melte d away before the plants were an inch high. A cold
frame that changes shape rapidly is tough to close off when zero F
temperatures are on the way.

Again, if people have proven solutions to my concerns, lets hear them. As a
designer, I can only recommend what I know works and I have no business
recommending anything that is a question, even a small question, in my mind.

For Mother Earth, Dan Hemenway, Yankee Permaculture Publications (since
1982), Elfin Permaculture workshops, lectures, Permaculture Design Courses,
consulting and permaculture designs (since 1981), and now correspondence
courses via email. Next live training: Paraguay, Sept. 1998. Internships
available. Copyright, 1997, Dan & Cynthia Hemenway, P.O. Box 52, Sparr FL
32192 USA YankeePerm@aol.com

We don't have time to rush.i




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