[Cob] Exterior finishes for insulated cob

[Bernhard Masterson]

Hello Sky,
  I live in temperate Portland, Oregon and share your views about the value of insulation in addition to thermal mass.  Here are a couple suggestions/options:
  - attach willow withies, bamboo, or other flexible sticks/reeds to the framing like lathe and plaster over the lathe to create a sealed cavity for the celulose.  A not so natural alternative is metal lathe.
  - instead of using cellulose you could use woodchips and clay.  Often called chip-slip, the clay drops the r-value but helps with bugs, moisture, and fire.  Chip-slip sets up so you can plaster directly onto the surface with a clay or lime plaster.
  - use a technique called bale-cob that creates a wall with cob on the interior and a bale or 1/2 bale on the exterior.  Then you could plaster the bales.
  - Do you know of Larson-Trusses? often used in straw-bale building to create thick wall cavities with less wood and less thermal bridging?  You might consider them for the framing.

- Bernhard 



Get under a sustainable lifestyle umbrella, the carbon is going to hit the fan.

____________________________________http://bernhardmasterson.com

Natural building instruction and consultation


> Date: Sat, 8 Jan 2011 17:24:15 -0800 (PST)
> From: Sky Orndoff <skyorndoff at yahoo.com>
> Subject: [Cob] Exterior finishes for insulated cob
> To: coblist at deatech.com
> Message-ID: <996410.67929.qm at web161202.mail.bf1.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
> 
> Hi!
> 
> I'm thinking about making a cob building in Montana.  I'm thinking cob because I 
> like the sculpting and the thermal mass.  Because it will be in Montana, and 
> because I'm an energy auditor who believes in insulation more than thermal mass, 
> I'm interested in insulating it thickly, probably with a shredded cellulose.  I 
> think I'll use wood 1.5"x12"s to frame a cellulose wall onto the outside of the 
> cob. We have a lot of dead and dying trees that are being logged already and can 
> be delivered to a friends sawmill for free.  I'll probably put cellulose between 
> the boards about 24" OC.  What I would like advice on is an appropriate exterior 
> cladding or siding or exterior coating for the celulose insulated wall.  I want 
> to do a floorplan with curved walls, keeping the walls vertical, so the cladding 
> will have to be flexible in one direction.  What would people advise for this?  
> Something with sand-clay?  Some type of product?  Suggestions for other 
> solutions than the one I'm thinking of now?
> 
> Thanks for your consideration,
> 
> JS Orndoff