[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

GBlist: re:Strawbale not good for humid,mixed heating/cooling climates




on Sat, 10 May 1997, John Bower wrote:
re: If my climate were drier, I wouldn't be a crier

>    I certainly don't have anything against straw bale as a building
>    material, but I suspect that there are going to be some failures
>    because of our imperfect knowlenge, or because some houses are going
>    to be built without using the knowledge we've already gained knowledge
>    that still isn't fully diffused throughout the building community.
>    Personaly, I can't afford to risk building a house based on imperfect
>    knowledge.

There is a saying amongst SBers (attributed to Tod Neubauer) that states:

     "It is better to be crudely right
          than precisely wrong".

I don't quite know how to say it politely, (so I won't try to) but I can
state with conviction that the points presented by Fred Lugano (re: Straw
Bale worries/failures) fall into a category described by the latter;
"precisely wrong". 

John Bower is probably correct in assuming that there will be SB building
failures for the reasons stated. However, I'm pretty sure that building
failures due to (mis)application of "imperfect knowledge" is not exclusive
to SB.

I would suggest that building a structure out of baled straw (ie barn-sized
toilet paper rolls for livestock) is a notion that is so seemingly absurd
(on the surface) that prospective builders have to jump through more
rigourous hoops (in addition to the standard ones) with Building Officials,
mortgage lenders and insurers in order to get their plans approved. 

We can be thankful for such intense scrutiny as it probably has served to  
"weed out" some of the more "hair-brained" schemes. 

Since this most recent revival of SB construction (ie SB built in wide-
ranging climatic conditions)is still so young, it's unlikely that the
Usually Dour Bion Howard will get his wish for documented SB failures.
                                   *
As others have already pointed out the inaccuracies in Fred Lugano's post
(re: stucco failures, VDRs, etc.) I'll limit my response to the following:

on Fri, 09 May 1997 
Lugano@ix.netcom.com wrote:
[snipped & chucked]

>    Worry #2-low R-value. These walls are coming in at only R-12 due to
>    the large interstitial spaces between the straw.

I will assume that "these walls" that Frank is citing is a reference to 
the testing that was done by Jeff Christian et al at Oak Ridge National
Labs a short while ago.

It should be pointed out that the results of that test are an anomaly
amongst the tests that have been done to date* which peg the R-value
anywhere between 1.4 -2.9 per inch depending (of course) upon density,
moisture content, fibre orientation etc. 

     [*Tests to determine thermal resistivity of SB have been carried out
     by Joe McCabe for his Master's Eng. thesis (available for viewing at
     the  CREST website) ... Dr. Chris Watts of Tech. U. of Nova Scotia for
     the  National Research Council of Canada, ... + others.]

Given that a straw bale  is composed primarily of cellulose and trapped
insulating air, it hardly seems reasonable that a typical SB wall (which
may consist of 18" to 24" of straw) would have an R-value of 12, lower than
that of a log (ie very dense-packed cellulose) wall as our cellulose
evangelist/SB critic suggests.

Without going into specifics, there were a number of details on the Oak
Ridge test wall that contravene acceptable standards of SB practice. Even
the Oak Ridge researcher acknowledged that his results were unsatisfactory
and that the tests should be re-done.  (At the end of this month, such
testing will be done in the new NFRC-accredited ATI labs in CA, using the
appropriate ASTMs. )
                              *

As Tom Fisher mentioned, moisture concerns are foremost on the minds of
people building with SB in cold/wet/humid climates.

For those who are interested :

     "Thermal and Mechanical Properties of Straw Bales 
     As They Relate To a Straw House" CSAE Paper # 95-209
     by K.C. Watts, K.I. Wilkie, K. Thompson, J. Corson

presents, in addition to the subject matter of the title, results  of 
monitoring (humidity and temperature) of the walls of the first two-storey
load-bearing SB house... built in a Maritime Cold Climate locale (Nova
Scotia) ...and without VDRs on the walls.

Again, here in Canada, CMHC is currently providing some funding to carry
out blower-door testing and moisture monitoring in 8 SB houses in Nova
Scotia ..as well as some core sample inspections of Quebec SB walls and
concrete-encased SB floors that are over ten years old.
     
Last spring, CMHC tested 4 moisture monitoring systems/methods for the
purposes of making recommendations for economical means whereby SB
homeowners can monitor the moisture levels in their walls + gather data for
use by the community at large. (Report available free from CMHC)

On the other Wet Coast, moisture monitoring is actively being carried
out on SB structures in the Kootenays of BC and at Portland Community
College in Oregon.

I would urge interested parties to base their opinions on the suitability
of SB for mixed/humid climates on these findings rather than the
unsubstantiated rantings of one who has been shown to be somewhat less-than
accurate in his presentations.

Apologies (sigh, again) for the somewhat negative tone of this post but 
I was appalled by the amount of misinformation that was being heaped on us
by Mr. Lugano.

--
Rob  Tom
---------- * ------------
be417@FreeNet.Carleton.ca
Kanata,  Ontario,  Canada

__________________________________________________________________
This greenbuilding dialogue is sponsored by Oikos (www.oikos.com)
and Environmental Building News (www.ebuild.com). For instructions
send e-mail to greenbuilding-request@crest.org.
__________________________________________________________________