[Cob] DSCN0313

[Henry Raduazo]

(Pictures must be requested off list)
Janet: I believe that cob has an R-value of 1 per inch so 24 inches  
thick would be R-24. I am not sure where I read that, but R-value is  
beside the point. What we are talking about is bio-mass. You are  
heating this mass while you heat the air in your house. That is why  
all cob houses are passive solar because the sun heats the air and  
the walls during the day time and the walls heat the air during the  
night. If the heat is moving through your wall at a rate of 1 inch  
per hour then 12 inches of cob is about the most you will need  
because after 9-12 hours of gaining heat it is then night time and  
you are starting to loose heat.

	Fig. 1 below shows an 8 inch cob wall built against a 12 inch thick  
wall of straw bales. By placing the bales on their edge you actually  
get more insulation because the straws run transverse to the  
direction of heat migration. This structure actually has three  
bedrooms and I believe they are wider than 10 feet. 

	I believe that there are several places that give the R-values of  
straw bales and it is a heck of a lot higher than cob.
Ed


(Picture available upon request.)

On Jul 18, 2010, at 7:19 PM, Janet Standeford wrote:
Understood. But I'm getting this permitted and they want to be sure  
the insulation value is there and short of putting regular insulation  
into the wall I don't think I can convince them to let me do it with  
narrower walls. If anyone can get me true r and/or u value for cob,  
let me know.

Like the idea of the front tine tiller or cultivator. There should be  
quite a few people here working on it. I'm going to get the high risk  
youth out here with OIT so the kids can learn another way to build as  
they are already doing stick built.


Janet Standeford OR
www.buildingnaturally.info (Owned by you)
A resource for healthy homes.



On 7/18/2010 3:26 PM, Henry Raduazo wrote:
     "three feet thick"!!!!? Wow that is very ambitious and a lot of  
mixing. With good cob, you could support a 5 story building with that  
wall. Even with fair quality cob that seems excessive.
     I have a picture of a slightly larger building that Ianto built.  
The walls are about 2 foot thick, but at least one foot of that  
thickness is a wall of straw bales. It has many times the insulating  
value of a 3 foot thick wall of cob and plenty of strength to support  
the roof, and the 8-12 inches of cob has more than enough bio-mass to  
store a day's worth of solar heat. You have to buy a lot of straw,  
but I think you will get your money back in lowering the amount of  
wood you need to cut to heat your building.
     Also, consider a front tine tiller or cultivator if you are  
going to mix that much cob. I doubt that two people can foot mix that  
much cob in one season and still have time to do the roof and all the  
other stuff you need.
Ed