Cob Earth berming cob buildings?

[Don Stephens]

Way back on Tue, 5 May 1998, Speireag Alden wrote:

> Regarding what Don Stephens previously wrote:
> 
> >Besides the relatively tempurature-stabile storage area this provides, it
> >offers a number of additional benefits - no lateral pressure on the back
> >house wall, a place to run, modify and service plumbing, electrical, etc.,
> >a great place for a composting toilet, a heat plenium to incorporate in an
> >annualized passive solar heating system (using the resultant dry soil as
> >thermal storage/flywheel mass and a place for movable insulation on that
> >wall of the house, to receive or resist heat transfer from that soil mass.
> >
> >I've gone on long enough on peripheral elements on a site to be restricted
> >to cob, but if others are interested in these ideas related to earth-
> >contacted cob and other moisture-sensitive materials and/or techniques of
> >annualized/isolated-gain passive solar, I'd enjoy hearing from you on the
> >side. I'll finish by quoting some sage's (anybody know who?) caution to
> >"Beware of all advice, including this!"
> 
> Don- Very interesting. I am building an above-ground straw-bale structure
> which will someday be the attached accessory apartment to a larger house.
> Since bedrock is between zero and six feet down on our site in western
> central New Hampshire, I'm planning to excavate down to bedrock for the
> larger house, and then bury it as much as possible in a south-facing slope.
> I had thought that for the underground portions I would have to insulate w/
> blueboard or rockwool panels or somesuch, because straw bales would
> deteriorate almost inevitably as part of a below-ground wall.  So says the
> literature.  You seem to be saying that it's feasible.  Have you actually
> used any in this application in a heating climate like mine?  Any long-term
> monitoring? - Speireag Alden, aka <Joshua.M.Alden.91 at alum.dartmouth.edu>

Don replies:  I DO believe it IS feasible to use strawbales subgrade, IF
done right and with great care and I find it a MUCH more sustainable/
healthy/natural/economical way to insulate than with Dow's petrochemical
blue foamboards.  (I have also been building sub-grade with WOOD for over
25 years, with proper peotection and detailing, with no problems and
designed my first earth-sheltered homes in 1960.)

And yes, I have USED strawbales in this type of application (in a poly-
membrane-protected bermed south-facing structure wall and in a perimeter
run-off diverting, soil-insulating "umbrella" extending out from the
structure subgrade and again with protecting 4 mil. cross-laminated poly-
membranes, over and under. This was first done in a test module built in
the summer of '96, adjoining the housesite for a house which I designed
utilizing the same concepts and which is now under construction by its
owners.  (Site climate is perhaps a bit more mild than yours may be: 
Summer highs to ~ 100 degrees F, winter lows to -10/15 [ocassionally to
-40/-50 F.], 5' of snow on snowy winters and around 25" of average annual
precipitation)

The test module is fully monitored and has now gone through two winters. 
Its inside low temperature hovered at ~ 48 degrees F. (~ 11 C.) the first
winter (before the solar thermosyphon had a chance to preheat the soil)
and at 60 degrees F. (~ 17 C.) the second winter, with no occupancy and no
supplimental internal heat sources either year. 

The bales averaged ~ 10% moisture when installed and have not fluctuated
more than a percent or two since.  I realize this is not "long-term" 
monitoring yet, but it first occurred to me to use strawbales as a more
sustainable, natural insulation in subgrade applications in late '95. Did
anybody else out there come up with and test subgrade strawbales from an
earlier date, who can now report a longer history with this approach? 

I realize I've opened a can of worms here and it's not exactly on-topic
for the cob list, so I'll leave it at that for now and send you an off-
list, more detailed follow-up description of how we built the test module
and the data gathered from it on moisture and how it's working to use
summer solar for winter heating.  If there are other daring souls who'd
like a peek at that detailed, 12K report, drop me a line to my address
<dsteph at tincan.org> and I'll send it along.  Include a fax # and I'll send
a couple of sketch sections to clarify the verbage.    : } ....Don

> Nach sgrìobhaidh thugam 'sa Gàidhlig?
 
No sprechen this language, do you translate? - D