[GSBN] Anyone ever try a cob/straw-clay hybrid?

Tue Apr 30 06:00:50 UTC 2013

Here in Hungary we have several buildings - wooden loadbearing structure - locally made cob  between the poles - strawbale outside insulation and earth plaster. This work perfectly in hot summer and cold winter. 

See more:  http://belsoudvar.hu/references#r29   
"Nagyszik" bird-watching center in Balmazújváros

Agnes NOVAK, Dr. PhD
Moholy Nagy University of Art and Design, Budapest,
novag at labor5.hu
+36 20 933 1547

On Apr 30, 2013, at 7:10 AM, מיכל ויטל wrote:

Hello Bruce and friends
i have here in Israel 2 projects involve light straw as exterior / interior insulation, so it had to dry only from one side. one is with metal wall and the other with earth blocks.
(you can watch pictures of the second one here:http://www.vital-baron.com/projects/%D7%91%D7%99%D7%AA-%D7%91%D7%91%D7%A0%D7%99%D7%94-%D7%98%D7%91%D7%A2%D7%99%D7%AA--%D7%91%D7%93%D7%A8%D7%95%D7%9D. the website is only in hebrew at the moment bit if you scroll down there are images)
we had no drying problemsin our hot dry summer, but in the first project it was akready november and we had to wait 3 weeks for drying.
The combination of light straw with heavy wall is working very well thermaly

Michal Vital
Vital-Rosenberg Architects
Israel 

2013/4/30 Jacob Deva Racusin <buildnatural at googlemail.com>
I'm not sure if phasing is an option, but if so and the cob were allowed to dry for a season with the straw-clay applied the following year, the cob could turn from a drying liability to a drying asset, given the hydrophilic nature of the clay.  I'm really not sure if it would be better than a strong breeze (air-dried), but you'd certainly get that from the outside.  It would require phased drying, though, which may not play out well in the construction schedule...

Kevin, great to hear you are using rice hulls, our company has been looking into playing with them but haven't had the right job - that an transporting a container of rice hulls from two days' drive away has been unappealing.  But it sure seems like a material with lots of potential if the resource is available.

Jacob
Jacob Deva Racusin
New Frameworks Natural Building, LLC
P.O. Box 15, Montgomery, VT 05470
(802) 782-7783 (c)
(802) 326-2209 (h)
www.newframeworks.com
jacob at newframeworks.com
On 4/29/2013 1:32 PM, Paula Baker-Laporte wrote:
> My concern would also be that the straw clay would only be able to dry from one side and that the cob would add to the moisture content for a long time...too long to dry the wall out safely.
> Building the straw clay wall first and then adding something like adobe to the interior could work.
>  
> Paula
> 
> On Mon, Apr 29, 2013 at 10:07 AM, Chris Magwood <chris at endeavourcentre.org> wrote:
> My concern would be drying for the straw/clay. We have a hard time getting straw/clay to dry in our warm but humid summer. We count on a week per inch of wall thickness, and that's with both sides of the wall exposed. Sometimes we have to help things along with a fan on the interior because the drying is slower in the still air. With one side of the straw/clay up against cob (which may still be drying itself?) I would worry about the straw/clay not drying out at all before it starts to get mushy in there.
> 
> What about double wythe cob with a dry insulation in between? 
> 
> Chris
> 
> On 13-04-29 11:38 AM, Bruce King wrote:
>> 
>> 
>> A client in North Carolina (mixed climate, no earthquakes) wants to build a large assembly structure on load-bearing cob, which doesn't insulate too well.  He doesn't want to use bales with thick earthen plaster, either.
>> 
>> So our idea was to build a wall that would look like this, from inside to out:
>> 
>> 14" -- 18" of load-bearing cob
>> 8" -- 12" of light straw-clay
>> lime plaster
>> 
>> Has anyone already done this, or heard of it?  Any reports of comments?
>> 
>> Thank you!
>> 
>> Bruce King
>> 
>> (415) 987-7271
>> Skype: brucekingokok
>> Twitter: @brucekinggreen 
>> http://www.housetalkgreen.com
>> http://bruce-king.com/
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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> 
> -- 
> Chris Magwood
> Director, Endeavour Centre
> www.endeavourcentre.org
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> 
> -- 
> Paula Baker-Laporte FAIA,BBP
> Econest Architecture Inc.
> www.EcoNest.com
> paula at econest.com
> Phone: 541.488.9508
> 
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